Chytrid Fungus Analysis for Soule River Watershed, Southeast Alaska

Soule River Watershed 

Amphibian Data Report 

2009 

Submitted to: 

Alaska Power & Telephone Company 

193 Otto Street 

Port Townsend, Washington 

Submitted by: 

The Shipley Group 

56 North Main Street 

PO Box 908 

Farmington, Utah 

April 2009

TABLE OF CONTENTS 

Introduction and Background 1 

Boreal Toads 1 

Boreal Toads in Canada 1 

Boreal Toads in Southeast Alaska 2 

Chytrid Fungus 4 

Chytrid Fungus in Alaska 7 

Soule River Watershed Survey for Anurans 9 

(Boreal Toad, Wood Frog) and Chytrid Fungus 

(Batrachochytrium dendrobatidis) (BD) 

Water Chemistry 22 

Discussion 24 

Discussion Summary 31 

Literature Cited 40 

Appendix A 55 

PCR Assay Details from Pisces Molecular 

Appendix B 57 

Amphibian Declines, Chytrid Fungus, and Boreal Toads 

i

Tables 

Table 1. Documented Boreal toad records from 3 

Southeast Alaska. 

Table 2 ‐ Chytrid fungus infection for 3371 post 5 

metamorphic and adult amphibians 

Table 3 ‐ Survey of Amphibians Populations 6 

Table 4 – Survey of Anuran populations for Batrachochytrium 8 

dendrobatidis (BD) on the northwest Coast of North America 

Table 5 – Amphibian Chytrid fungus Batrachochytrium 13 

dendrobatidis (BD) Survey Data from Soule River Watershed, 

Southeast Alaska, July 2009 

Table 6 – Water Chemistry of Delta Tadpole Pond 22 

Table 7 – Boreal Toads (Anaxyrus boreas boreas) Observed 24 

in the Field, 2007‐2009 

Table 8 – Recent Major Amphibian survey for Chytrid fungus 28 

(Batrachochytrium dendrobatidis (BD) in Alaska and 

Western Canada 

Table 9 ‐ Total Field Effort at Soule River Watershed, 2007‐2009 32 

Table 10 ‐ Boreal Toads (Anaxyrus boreas boreas) Observed in 

the Field, 2007‐2009 34 

ii

Figures 

Figures A1 through A4 12 


Figures A8 through A 13 19 



Figure A26 through A27 22 

Map 1 11 

Map 2 15 

Map 3 16 

iii

Amphibians of Soule River Watershed, Southeast Alaska 

Introduction and Background 

The class Amphibia consists of three orders: salamanders and newts, anurans (frogs, toads, 

spadefoots), and caecilians (Gymnophiona). Caecilians are poorly known tropical legless 

amphibians with short tails, resembling fat earthworms. It appears that amphibians represent 

a major indicator or canary in the coalmine for ecosystem assessment and monitoring. 

Amphibians, as are all vertebrates, are susceptible to a wide range of diseases and individual 

mortality caused by: fungi, viruses, protozoans, bacteria, and macroparasites (e.g., trematodes). 

However, only the first three have been implicated in the widespread declines and extinctions 

of amphibian populations (Collins and Crump 2009). By far the main pathogen identified with 

amphibian declines and extinctions has been the chytrid fungus Batrachochytrium 

dendrobatidis. 

Boreal Toads 

The Boreal Toad (Anaxyrus boreas boreas) has a very extensive distribution, ranging from all of 

Southeast Alaska, all of British Columbia, and western Alberta in the north; south to northern 

California, most of Nevada north of the Mojave Desert, and the mountains of Utah; and east to 

western Montana, western and southern Wyoming, the Rocky Mountains of Colorado, and 

extending into the northern extreme of New Mexico. The two subspecies intergrade in 

northern California. The Boreal Toad is commonly referred to as the Western Toad in much of 

the literature. Nevertheless, the correct and taxonomically accepted nomenclature is that the 

Western Toad refers to both subspecies of Anaxyrus boreas. 

Boreal Toads in Canada 

The Boreal Toad in British Columbia and Alberta is considered secure, the species “can appear 

very common and abundant”, and all Canadian populations are apparently doing well, at least 

at the turn of the century (Wind and Dupuis 2002). Most of the following assessment is based 

on this report and its references. The Boreal Toad is widely distributed in British Columbia, 

especially in its central and southern portions. The toad is also relatively common in the 

northern portion and spills over into the southern Yukon. The northern populations are in 

valleys that receive high accumulation of annual snowfall, assuring safe winter hibernacula. 

The Boreal Toad has numerous occurrence records on the Pacific coast of British Columbia from 

the Washington state boundary north to Stewart, including Vancouver and Queen Charlotte 

Islands (Wind and Dupuis 2002, Figure 3). North of Stewart the distribution record picks up at 

Mount Edziza Provincial Park and continues north into the Yukon. The Boreal Toad distribution 

gap between Stewart and the Provincial Park may be a lack of surveys or a real absence. Boreal 

1

Toads, particularly for an amphibian, have good tolerance of brackish and even saltwater, and 

therefore, are quite capable of colonizing many islands from the large complex of islands 

available off the coasts of British Columbia (Wind and Dupuis 2002) and Southeast Alaska 

(MacDonald 2003, MacDonald and Cook 2007). They can swim for at least several hours in 

seawater (MacDonald 2003). 

The primary concern for the Boreal Toad was the south‐coast population of British Columbia 

and adjacent Vancouver Island. Boreal Toad numbers on the lower mainland of British 

Columbia and southern, eastern, and central, Vancouver Island, appear to be declining based 

on historical records. Amphibian and other biological surveys between 1998 and 2000 found 

that Boreal Toads were scarce. However, adequate long‐term data to quantitatively assess 

trends is lacking. 

The decline of Boreal Toads from coastal southern British Columbia, surrounding islands, and 

especially Vancouver, has primarily been attributed to human land use; habitat loss, 

degradation, and fragmentation. Human settlements typically drain and fill‐in wetlands, 

channelize rivers and streams eliminating quiet backwater sloughs and pools, and significantly 

alter landscape hydrology. Additionally, other anthropogenic‐related impacts are to blame: 

pollution and pesticides, road and highway mortality, and predators associated with or 

attracted to human developments (see Predation Section). 

Boreal Toads in Southeast Alaska 

Boreal Toads are widespread in Southeast Alaska, and range northward along the coast to 

Prince William Sound, including Montague and Hawkins Islands; with the edge of their range a 

short distance north to the Tasnuna River (a tributary of the Copper River) and west to the 

Columbia Glacier (MacDonald 2003). 

MacDonald (2003) reported that Boreal Toads “are common and widespread on the mainland 

and islands of Southeast Alaska”. Boreal Toad records are certainly widely distributed 

throughout Southeast Alaska (MacDonald 2003, MacDonald and Cook 2007). There are 70 

museum specimen records in Southeast Alaska documented by geographic location (usually 

including latitude and longitude) and a distribution map in MacDonald and Cook (2007, pages 

127‐128). The records are particularly prevalent along the coast and near settlements. Records 

near the British Columbia border and interior, especially in the southeastern portion of 

Southeast Alaska are absent, because of the lack of surveys. 

Island Records of Boreal Toads for Southeast Alaska, museum specimens, MacDonald and Cook 

2007: 

Admiralty Bushy Etolin Hoyspur 

Annette Chichagof Hassler Kosciusko 

Baker Chilkat Heceta Kuiu 

Baranof Dall Herbert Graves Kupreanof 

2

Long 

Mary 

Mitkof 

Noyes 

Prince of Wales 

Revillagigedo 

Sergief 

Suemez 

Sullivan 

Vank 

Woronkofski 

Wrangell 

Yakobi 

Zarembo 

Only five records are documented (Table 1) in the general southeastern region of Southeast Alaska, 

none of them in the Soule River Watershed area. The number of museum specimens are in parenthesis. 

Location North 

Latitude 

West 

Longitude 

Hyder (1) 55.9200 130.0200 

Hyder Area (1) 

Salmon River, at mouth of Texas River 

Approx. 40 miles west of Hyder (1) 

Approx 5 miles east of Behm Canal 

Approx. 25 miles north of Chickamin Bay 

Boca de Quadra (3) 

A bay approximately 30 miles north 

of Portland Fiord inlet 

Smeaton Bay (1) 

Head of Blackwell Arm, 

just north of Boca de Quadra 


of Portland Fiord inlet 

‐‐‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐‐‐‐‐‐ 

56.0269 130.9844 

55.2000 130.4700 

55.2800 

Table 1. Documented Boreal toad records from Southeast Alaska. 

130.6300 

With the exception of the Hyder sites, the other three sites are west of the mountains where the Soule 

River Watershed originates, and the Soule River flows east to the Portland Canal. 

The distribution of the Boreal Toad is or at least was certainly widespread in Southeast Alaska (see 

above). However, the species’ actual abundance in terms of population density estimates or encounter 

rates in the field, particularly in remote areas, are not actually known for most of their Alaskan range. 

MacDonald (2003) reported that they were “widespread and common” in Southeast Alaska. There is 

anecdotal evidence provided by long‐time residents in the area of Skagway and Klondike Gold Rush 

National Historical Park in northern Southeast Alaska that Boreal Toads were “considerably more 

common 20 years ago compared to today” (Hahr 2006). In the same report, a retired National Park 

Service trail crew leader recalled that recent metamorph toads were so abundant in summers that 

3

thousands of them blanketed portions of trails in Klondike Gold Rush Park, and it was impossible to 

avoid stepping on them. The rumored and perceived declines of Boreal Toads in Southeast Alaska 

prompted Klondike Gold Rush Park to initiated surveys in 2003. Intensive surveys over two summers at 

39 potential breeding sites, found tadpoles in only six of the sites (Hahr 2006). 

Alaska Department of Fish and Game (ADFG 2007) initiated a pilot study in 2004 to monitor three sites 

in Southeast Alaska: Prince of Wales Island, Admiralty Island, and Upper Lynn Canal (Chilkat Valley and 

Skagway area). Sampling protocols were developed and preliminary information was provided in this 

report. Four hundred and fifty random and “opportunistic” selected wetlands sites were identified over 

an area of 9642 km 2 . Encounter rates of Boreal Toads in wetlands were preliminary estimated at 20‐25 

percent in the first year of the project (2005). The parameter “encounter rate” was not defined, but a 

good assumption was that toads were found at 20‐25 percent of the sites that were visited in this first 

year. In the second year of the study (2006), the encounter rate was reported as 5‐20 percent based on 

the specific sites that were visited. The data for the third year of the study (2007) reported that a total 

of 544 wetlands sites were surveyed in the three years of the study over an area of 9642 km 2 . There 

were 283 sites surveyed in the last period. Boreal Toads currently occupied 17.5 percent of the 

landscape, with significant variation across the study area. Breeding habitats represented only 8.1 

percent of the landscape, and the toads favored “shallow margins of larger bodies of water”. The 

highest occupancy for Boreal Toads was on Admiralty Island (26.3%), while the lowest was on Prince of 

Wales Island (14.2%). Wood Frogs (Lithobates sylvaticus) and Northern Roughskin Newts (Taricha g. 

granulosa) were also observed in the surveyed wetlands over all three years, and the newts occupied 

nine percent of the landscape. 

Additional information was available in the abstracts of the Alaska amphibian conference held in 

February 2006 (Tessler 2006). Sanjay Pyare, the project leader of the ADFG sponsored study discussed 

above, and others, discussed the paucity of data for Alaska amphibian distribution and abundance 

patterns. The major stumbling block was, of course, the large size of landscapes to sample and their 

remoteness, access, and ruggedness. Pyare provided more details from the first year (2005) of the study 

discussed above. Encounter rates refer to the occupancy rates of visited wetlands habitat patches. 

Amphibian surveys were conducted on 260 (105 random, 155 opportunistic) wetlands habitat patches in 

the three study sites during the prime breeding period, 1 May – 15 July. Encounter rates of all life‐history 

stages of Boreal Toads ranged from 18‐21 percent among the three areas. Encounter rates for evidence 

of breeding (eggs, tadpoles, metamorphs, yearlings) were 10‐18 percent. Therefore, from these data, 

the approximate encounter rates of adults ranged somewhere between 0‐11 percent. Among randomly 

selected wetlands habitat patches in all three areas, both toad (all stages) and recent breeding 

occurrences were encountered at the rate of 10‐40 percent. Roughskin Newts were encountered at 15‐ 

17 percent occupancy on the random patches on Admiralty and Prince of Wales Islands. Pyare 

concluded that their data underestimated true occupancy, because the data were not corrected for 

detection error, which they were still evaluating. Detection error is the major and serious concern in all 

surveys using patch occupancy modeling, and is a function of both species and habitat characteristics 

(Thompson 2004, MacKenzie et al. 2006). 

Chytrid Fungus 

A species of chytrid fungus (Batrachochytrium dendrobatidis) (BD) has been conclusively implicated in 

amphibian declines throughout the world (Young et al. 2001, Daszak et al. 2003, Briggs et al. 2005, La 

4

Marca et al. 2005, Lips et al. 2006, Rachowicz et al. 2006, Skerratt et al. 2007, Collins and Crump 2009 

[pages 159‐174], Rosenblum et al. 2010). 

Chytrid fungi represent a primitive group of fungi, Chytridiomycota, with five orders, approximately 

1000 species, and BD is unique and phylogenetically distinct (James et al. 2006). Chytrids are closely 

related to protozoans, because of their ancestry. Chytrid fungi are globally distributed from the tropics 

to arctic regions in diverse habitats. Most species are probably terrestrial and saprophytes, breaking 

down and feeding on keratin, chitin, and cellulose. Some soil chytrids are plant pathogens. There are 

freshwater and marine species that are parasites of algae and plankton. BD is the only known chytrid to 

parasitize vertebrates (Longcore et al. 1999). 

Time 

Period 

Quebec Rest of Canada 

Number BD Percent Number BD Percent 

Examined Infected Infected Examined Infected Infected 

1895‐1959 38 0 0 136 0 0 

1960‐1969 217 29 13.4 316 16 5.06 

1970‐1979 30 8 26.7 126 2 1.59 

1980‐1989 15 6 40.0 45 0 0 

1990‐2001 1698 302 17.8 0 ‐‐‐‐‐‐ ‐‐‐‐‐‐ 

1960‐2001 1960 345 17.6 487 18 3.70 

Time 

Period 

United States 

Number BD Percent 

Examined Infected Infected 

1895‐1959 29 0 0 

1960‐1969 122 1 0.820 

1970‐1979 89 10 11.2 

1980‐1989 63 8 12.7 

1990‐2001 7 1 14.3 

1960‐2001 281 20 7.12 

Table 2. Chytrid fungus (Batrachochytrium dendrobatidis) infection for 3371 postmetamorphic and 

adult amphibians collected from 1895 to 2001 from Canada, United States, and 23 other countries. 

The data in Table 2 is summarized from Ouellet et al. (2005, Table 3). 

Importantly, Wind and Dupuis (2002) only discussed chytrid fungus as it pertained to amphibian 

populations and declines outside of Canada, (e.g., continental United States, Neotropics, and Australia). 

They did not mention any identification of chytrid fungus infections in Canada. 

5

The first northernmost record for chytrid fungus was in a Boreal Toad from northeastern British 

Columbia (Raverty and Reynolds 2001). A single specimen that exhibited a prominent mid‐dorsal 

cutaneous ulcer was brought in for examination in August 2000. 

Slough (2009) surveyed 11 sites in northwest British Columbia and one in extreme southeastern Yukon 

for chytrid fungus infection in three species of amphibians: Boreal Toad, Wood Frog (Lithobates 

sylvaticus), and Long‐toed Salamander (Ambystoma macrodactylum). The results are summarized in 

Table 3. 

Area Species Adult Metamorph/Juv. Larvae 

‐ + BD ‐ + BD ‐ + BD 

Northwest Boreal Toad 12 5 1 12 ‐‐‐‐ ‐‐‐‐ 

British 

Columbia 

Wood Frog 1 0 ‐‐‐‐ ‐‐‐‐ ‐‐‐‐ ‐‐‐‐ 

(11 sites) 

Southeast 

Long‐toed 

Salamander 

2 0 ‐‐‐‐ ‐‐‐‐ ‐‐‐‐ ‐‐‐‐ 

Yukon 

Boreal Toad 0 1 ‐‐‐‐ ‐‐‐‐ 30 0 

(1 site) 

Wood Frog 0 6 ‐‐‐‐ ‐‐‐‐ ‐‐‐‐ ‐‐‐‐ 

Table 3. Survey of Amphibian Populations for Batrachochytrium dendrobatidis (BD) in Northwest 

British Columbia and Southeast Yukon, Canada. 

Amphibian surveys were conducted during the summers of 2007 and 2008 at 11 sites in northwestern 

British Columbia, and one site in southeastern Yukon (Table 3). 

The (+BD) column indicates the number of individuals that were found infected with the fungus. 

The (‐) column indicates number of individuals that tested negative for BD. 

Because of small sample sizes metamorphs and juveniles were combined. 

Three species were found: Boreal Toad (Anaxyrus boreas boreas), Wood Frog (Lithobates sylvaticus), and 

Long‐toed Salamander (Ambystoma macrodactylum). 

Data are from Slough (2009), where latitude and longitude of the 12 sites are documented. 

The data of Raverty and Reynolds (2001) and Slough (2009) indicate that chytrid fungus occurs as far 

north as northern British Columbia and southeastern Yukon, and both Boreal Toads and Wood Frogs are 

carriers. Table 2 also indicates the difficulty of obtaining significant sample sizes across species and life 

history stages. Five of 17 adult Boreal Toads were infected with chytrid fungus, while two of three 

juveniles were, and all 10 metamorphs examined were infected in British Columbia sites. The single 

Wood Frog and two salamanders found at these sites were not infected. At the Yukon site, the single 

adult Boreal Toad found was infected, but 30 tadpoles were not. All six Wood Frogs found at this site 

were infected. 

Only a single individual that tested positive for fungus showed any symptoms, sloughing skin on the 

thigh of a Boreal Toad. No other individual had any visual signs of the disease, such as redness on the 

legs or lethargy. The author concluded that the low populations encountered may or may not indicate 

recent declines, but the data is insufficient to implicate chytrid fungus. 

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Deguise and Richardson (2009) examined 32 adult male Boreal Toads during the breeding season from 

Alice Lake Provencial Park, southwestern British Columbia for chytrid fungus. Nine (28%) of the 

individuals tested positive for the fungus, even though none of them showed any external symptoms of 

pathology. Interestingly, body condition of fungus infected toads did not differ statistically from toads 

that were not infected with the fungus. The dates for collecting field data were not presented. 

Chytrid Fungus in Alaska 

The first documented occurrence of chytrid fungus (BD) in Alaska was found in a dead subadult male 

Wood Frog near a pond on the Kenai National Wildlife Refuge, Kenai Peninsula, on 25 July 2002 (Reeves 

and Green 2006). Ventral skin in the pelvic patch area and hind limb digits showed epidermal lesions 

with mild hyperkeratosis. Histological examination diagnosed the lesions as mycotic hyperkeratotic 

epidermitis due to infection by BD. No other species of amphibian is known at the wildlife refuge. 

Boreal Toads have never been documented for the Kenai Peninsula, but they occur just to the east on 

Montague Island and in the Prince William Sound area. 

Additional surveys for BD occurrence were conducted from 11 May to 21 July 2006 at three National 

Wildlife Refuges: Kenai, Tetlin, and Innoko (Reeves 2008). Wood Frogs were collected opportunistically 

near the vicinity of 29 breeding ponds. This is the only species of amphibian in interior Alaska 

(MacDonald 2003). Tetlin is located east‐northeast of the Kenai Peninsula, north of the Wrangell 

Mountains, and close to Yukon province of Canada. Innoko is northwest of the Kenai Peninsula and east 

of Norton Bay. Ten Wood Frogs from Tetlin and nine from Innoko were examined, each specimen from 

a different pond. None were infected with BD. All of these 19 pond sites are remote, requiring a 

combination of aircraft and watercraft for access. 

Ten pond sites were surveyed at Kenai. These were different ponds from the 2002 pond with BD 

discussed above, but the access road was the same. One of the four ponds that had road access had BD, 

while two of the six remote ponds had BD. At the three ponds that had BD infections, all captured 

Wood Frogs were contaminated, but sample sizes were small with respective captures of one, two, and 

four. At the seven Kenai ponds without BD infection, 22 frogs tested negative, with sample sizes of: 1, 1, 

1, 2, 3, 6, 8. The three infected ponds were near Swan Lake recreational canoe route or its access road. 

One pond was adjacent to the road, and the two remote ponds were within 3 km of the road and 1 km 

of the canoe trail. Two of the four remote ponds that tested negative had essentially no human access. 

The three ponds with road access that tested negative are in an operating oil field with no public access. 

It is unlikely that oil workers and the non‐amphibian researchers that use this area go into the wetlands 

sampled in this study. Amphibian researchers have visited the oil field wetlands since 2000 and the 

other remote wetlands since 2004, but hygiene protocols to avoid BD were always followed. 

Thirty Wood Frogs, mostly metamorphs, were surveyed for BD in August 2006 at 26 known localities in 

the Wonder Lake region of Denali National Park (Chestnut et al. 2008). Frogs were found at 20 of the 

sites. BD was not detected in the 12 frogs collected at roadsides, nor at the 18 collected in remote areas 

up to 4.5 km from the road. The authors concluded that additional surveys, higher sample sizes, and 

examining individuals across all life history stages are required. 

Adams et al. (2007) summarized the U.S. Geological Survey’s Amphibian Research and Monitoring 

Initiative for the northwest coast of North America. Four general areas, from Vancouver Island to 

7

Skagway Alaska were surveyed for BD collecting all life history stages of anurans. BD was found in three 

of the four areas, in 11 of 22 populations, and in 52 of 242 (21%) individuals tested for BD (Table 4). 

Area Pop. 

Num. 

Skagway 

Region 

Northeast end 

of Southeast 

Alaska, 

including 

adjacent 

British Columbia 

Admiralty 

Island 

Prince of 

Wales 

Island 

Species Adult Juvenile Larvae 

‐ + BD ‐ + BD ‐ + BD 

1 AnBo 8 7 10 0 0 0 

2 AnBo 13 4 0 0 0 0 

3 AnBo 13 4 0 0 0 0 

4 AnBo 0 3 5 2 0 0 

5 AnBo 1 0 0 0 0 0 

6 AnBo 1 0 2 0 0 0 

7 AnBo 0 0 9 1 0 0 

8 AnBo 0 0 2 0 0 0 

9 AnBo 0 0 2 8 0 0 

10 AnBo 2 0 0 0 0 0 

10, 11, 12 RaLu 5 0 3 0 0 0 

10, 12 LiSy 1 0 1 0 0 0 

13 AnBo 17 0 0 0 0 0 

14 AnBo 10 0 0 0 0 0 

15 AnBo 2 3 3 7 0 0 

16 AnBo 14 5 1 0 0 0 

17 AnBo 16 6 0 0 0 0 

Vancouver Is., 18, 19, 20 AnBo 1 0 10 0 10 0 

southern 18, 19, 21, 

22 

RaAu 6 2 2 0 20 0 

Table 4. Survey of Anuran Populations for Batrachochytrium dendrobatidis (BD) on the Northwest 

Coast of North America. 

Amphibian surveys were conducted during the summers of 2005 and 2006 at four general areas, for 22 

populations, and all life history stages. 

Admiralty and Prince of Wales Islands are part of Southeast Alaska, and Vancouver Island belongs to 

British Columbia. Pop. Num. refers to a specific anuran population that was surveyed. 

The (+BD) column indicates the number of individuals that were found infected with the fungus. 

The (‐) column indicates number of individuals that tested negative for BD. 

Four species were found: Boreal Toad (Anaxyrus boreas boreas), Wood Frog (Lithobates sylvaticus), 

Columbia Spotted Frog (Rana luteiventris), and Northern Red‐legged Frog (Rana aurora). 

Data are from Adams et al. (2007), where latitude and longitude of the 22 populations are documented. 

Anuran nomenclature is from CNAH (2010). 

8

Most of the anurans examined were Boreal Toads. Out of the 10 Boreal Toad populations examined in 

the Skagway region, six had BD infections. However, only eight individuals were tested at the four 

populations where BD was not found, while 89 toads were examined at the six sites that were infected. 

The overall BD infection rate of the 97 Boreal Toads examined in the Skagway region was 30 percent. 

The 10 ranids found were not infected. These individuals along with two adult Boreal Toads were from 

populations 10, 11, and 12 where BD infections were not found. Two populations on Admiralty Island 

were examined, and 27 adult Boreal Toads were not infected with BD. The three populations of Boreal 

Toads on Prince of Wales Island were all infected. The overall infection rate of the 57 examined was 37 

percent. The five anuran populations examined in southern Vancouver Island were infected at a rate of 

3.9 percent, but most of the individuals were tadpoles and juveniles, life stages that may demonstrate 

lower infection rates than adults, especially tadpoles. Only a single adult Boreal Toad was available for 

examination from a total sample size of 21, and six adult Northern Red‐legged Frogs were examined 

from a total sample size of 30. Interestingly, based on the entire data set, the overall infection rate of 

juveniles (18/68, 26%) was similar to adults (34/144, 24%). Tadpoles were not infected (0/30). 

Over all these surveys, none of the anuran specimens handled appeared sick or morbid, and dead 

anurans were never observed. The authors did not mention epidermal skin lesions or any abnormal 

condition of the skin. However, there is still a great deal to learn concerning BD epidemiology. 

The 2007 Alaska Department of Fish and Game Performance Report discussed above (see Section Boreal 

Toads in Southeast Alaska) stated that ten sites were surveyed for chytrid fungus, all these sites were 

infected, and approximately a third of all individuals tested were infected (ADFG 2007). The report did 

not discuss the sites, dates, or the pathology of the infected individuals. For example, were the toads 

asymptotic (no symptoms of the fungus), or did they demonstrate mild to severe ventral skin lesions or 

reddening of the skin; conditions that demonstrate successful attack by chytrid fungus. The 2006 Alaska 

Amphibian Conference did not report on chytrid fungus in Alaskan anurans, and only discussed its 

pathogen effects globally and in the United States (Tessler 2006). 

Soule River Watershed Survey for Anurans (Boreal Toad, Wood Frog) and Chytrid 

Fungus (Batrachochytrium dendrobatidis) (BD) 

Observations of Boreal Toads in 2007 and 2008 were opportunistic while searching for wildlife and 

collecting a wide variety of ecological data. The collecting of ecological data in the field consisted of: 

forestry and river measurements, fisheries and big game assessments, documentation of plant 

communities, avian surveys, and opportunistic wildlife and amphibian surveys. 

Over 30 Boreal Toad metamorphs (< 2 cm) were observed while camping 12‐14 September 2007 on the 

delta of the Soule River. These juveniles transformed from tadpoles during the summer (July – August), 

and were observed on the delta in tall dense grass, especially in the association of several large Sitka 

spruce with well developed litter. All metamorphs were very similar in size and in the same location, 

suggesting that they were from a single egg deposition. The Delta has tidal flooding and numerous pools 

develop at the mouth of the Soule River along with brackish marsh habitat. 

Field studies were conducted with three personnel from 21 July – 5 August 2008 in the Soule River 

Watershed. We were camped along the North Fork of the Soule River and at No Name Lake. Habitats 

where ecological data were collected included: montane conifer forest, North and West Forks of the 

9

Soule River, riverine and lacustrine riparian, ponds and wetlands complexes, seeps, and muskeg. Pond 

habitats consisted of beaver ponds, backwaters of the river, or pools at the base of steep slopes that 

filled with snow melt and groundwater seepage. Intense searches were made for amphibians when 

ponds and wetlands were encountered. 

Similar field investigations were conducted in 2009 with two to four field personnel. See Map 1. 

Additional field work was added in 2009 and included: characterization of wetlands, intensive amphibian 

and chytrid fungus surveys, measurement of tidal currents at the Soule delta, and acoustical Goshawk 

surveys. Additionally, we were trying to observe any and all wildlife that we came across, including 

amphibians, and specifically searched for amphibians in quality habitat, such as ponds, wetlands, and 

muskeg. 

The only amphibian species observed in the watershed in 2008 was the Boreal Toad (Figure A1). Boreal 

Toads blend in well with their habitat and are difficult to see, especially if they do not move (Figures A2 

and A3). Adults were seen opportunistically on three different occasions along the North Fork River. All 

three toads appeared to be active and healthy. They did not have any traces of ventral or dorsal skin 

lesions, or ventral skin reddening. Careful searching for amphibians in what appeared to be good 

habitat failed to find any specimens of adults or tadpoles. Considering the large amount of time spent in 

the field, we concluded that amphibians are very rare in the North Fork and No Name Lake area of the 

Soule Watershed. 

Field investigations were conducted in the Soule River Watershed 14‐29 July 2009. The most intense 

amphibian surveys were conducted from 14 to 19 July. The amphibian survey work was a component of 

a much more extensive ecological assessment conducted with four researchers that covered montane 

conifer forest, wetlands, riparian, river, estuary, brackish marsh, fisheries, wildlife, and goshawk surveys. 

Active searches for amphibians were conducted in the following habitats: montane conifer forest and 

forest litter, riverine and lacustrine riparian, ponds and wetlands complexes, seeps, muskeg, river 

channels and small streams, and river delta brackish marsh. However, most of the search time for 

amphibians during this time period was opportunistic, and occurred when other ecological metrics were 

being collected in the field. 

Captured amphibians were swabbed for chytrid fungus, Batrachochytrium dendrobatidis (BD), (Figure 

A4) using currently established protocol (Brem et al. 2007, Brede et al. 2009). The samples were sent to 

Pisces Molecular, Boulder, Colorado, for detection of BD by PCR analysis. Pisces Molecular procedures 

are in Appendix A. Habitat and toad pictures were also from Carstensen (2009). The data are reported 

in Table 5. 

10

Map 1. Survey routes for 2009 Field work 

11

Figure A1 Boreal Toad Figure A2 

Figure A3 Figure A4 

12

Species Date Identification 

and field notes 

ANBO 14 July A 

Adult 

ANBO 15 July B 

Adult 

ANBO 15 July C 

Adult, carcass 

ANBO 15 July D 

Adult 

ANBO 18 July E 

Adult 

ANBO 18 July F 

Adult 

ANBO 18 July G 

Adult 

TAGR 15 July H 

Adult 

TAGR 15 July I 

Adult 

Pisces 

Code 

GPS Chytrid 

Analysis 

(PCR) 

A (068) 95640 N 55 0 51.639’ 

W 130 0 10.847’ 

B (076) 95633 N 55 0 49.923 

W 130 0 11.518’ 

C (079) 95637 N 55 0 49.855’ 

W 130 0 11.456’ 

D (112) 95632 N 55 0 49.550’ 

W 130 0 10.667 

E (049) 95635 N 55 0 49.119’ 

W 130 0 10.012’ 

F (053) 

(054) 

95636 N 55 0 49.129’ 

W 130 0 10.007’ 

G (026) 95634 N 55 0 49.804’ 

W 130 0 10.889’ 

H (021) 

(023) 

95638 N 55 0 50.546’ 

W 130 0 11.366’ 

I ‐‐‐‐‐‐ 95639 N 55 0 50.509’ 

W 130 0 11.398’ 

+++ 

Very Strong 

Negative 

Negative 

Negative 

++ 

Strong 

Negative 

Negative 

Negative 

Negative 

Table 5. Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) Survey Data from Soule River 

Watershed, Southeast Alaska, July 2009. 

Identification and Field Notes: 

A AnBo, Spec #1, SVL = 65mm, Figure A5 

Early‐seral surface of a dewatered pond, near Sitka alder fringe 

B AnBo #2, SVL = 65mm, Figure A17 

Short willow thicket and snags 

Identification and Field Notes: (continued) 13

C AnBo carcass, moldy, Figure A7 

sphagnum bog 

D AnBo, adult, Figure A4 

Soule River Main Stem, West Bank, just downstream of Gauging Station 

Habitat: forest litter, just above river; beaver ponds along river; well‐developed forest of western 

hemlock and mountain hemlock, scattered Sitka spruce, pockets of subalpine fir; good shrub and 

seedling layer; boulders and downed snags were abundant 

E AnBo #5, SVL = 75mm, female, Figure A6 

Swam into deep pond and dove, but came up 

This pond was one of about 20 clear water ponds with buckbean margin, 

in poor fen with Sphagnum but lots of vascular forage species 

F AnB0 #6, SVL = 68mm, male, Figures A11 and A12 

hopped into a shallower buckbean pond, poor fen 

G AnBo #4, SVL = 80mm, female, Figure A15 

Right on the margins of the tadpole pond, 

sedge wetland encompassed by dense Sitka alder thicket 

pond on main stem of river 

H TaGr #1; male, buckbean pond, Figures A21 and A22 

I TaGr #2; female, on land near pond with buckbean 

Buckbean (Menyathes trifoliata) 

Sitka Alder (Alnus crispa) 

Species Codes: 

Boreal Toad (Anaxyrus boreas boreas) = ANBO 

Northern Roughskin Newt (Taricha granulosa granulosa) = TAGR 

All data July 2009 

PCR Chytrid Fungus Analysis by: Pisces Molecular, Boulder Colorado 

‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 

A total of nine amphibians were swabbed for chytrid fungus identification: six adult Boreal Toads, an 

adult carcass, and two adult Northern Roughskin Newts. Four toads and the newts were found negative 

for chytrid fungus. Two adults were positive for BD. All swabbed toads, both negative and positive for 

BD, appeared healthy and active with no ventral or dorsal epidermal lesions or reddening of ventral skin. 

The toad in Figure A4 (ID D) tested BD negative. The toad in Figure A5 (ID A) tested as “Very Strong” for 

BD infection, and the toad in Figure A6 (ID E) tested “Strong” for BD. The moldy toad carcass, in active 

decay and covered with fungus, tested negative for BD (ID C, Figure A7). This is of interest, because BD 

originally evolved as a saprophyte that breaks down keratin, chitin, and other tough tissue (Berger et al. 

2005a). See Map 2 and 3 for locations of identified species A through I. 

14

Map 2‐ locations of species, example (1A, 1B, 1C etc) is species located on day 1 Soule River, (2A, 2B, 2C 

etc) is species located on day 2 Soule River. 

15

Map 3‐ locations of species, example (3A, 3B, 3C etc) is species located on day 3 Soule River survey. 

A, B, C etc is location of Boreal Toad see page 17 and 18 for field notes. 

16

Boreal Toad A, the strongest BD infected specimen, was also the most northern specimen captured in 

the Soule Watershed. The toad was found in a beaver pond wetland site on a bench above and near the 

bottom of the West Fork of the Soule River. The habitat was an old beaver pond that lost most of its 

water, note breached dam on the left (Figure A8). 

The other BD infected toad (E) was the most southeastern toad captured. It was in a wetland fen on a 

bench above the west bank of the main stem of the Soule River (Figure A9). The Soule River cannot be 

seen, but its canyon is in the upper background of the figure. There were approximately 20 small clear 

shallow buckbean ponds in the fen, the right side of Figure A9. Figure A10 is an example. The BD 

infected toad was found in one of the deeper ponds. Another toad was captured in a nearby pond. This 

toad was BD negative (ID F, Figures A11 and A12). 

A BD negative toad (ID D, Figure A4) was captured in the forest litter also on the west bank, upstream, 

and just below the gauging station. The habitat was a well‐developed hemlock forest with both species 

and scattered Sitka spruce (Figure A13). The site was just above the main stem of the Soule River, and 

there were beaver ponds just above the bank of the river (Figure A14). 

Just upstream again on the west bank of the main stem of the Soule River was another beaver pond 

wetland complex. Toad G (Figure A15) was captured here. The habitat is shown in Figure A16. 

Just to the west, toad B (Figure A17) was captured in another beaver pond wetland complex, on the 

south bank of the West Fork just upstream of its junction with the North Fork (Figure A18). The toad 

was in a thicket of short willows in a clear water beaver pond (Figure A19). The toad carcass (ID C, 

Figure A7) was found at a small bog 150 meters southeast and uphill from this site (Carstensen 2009). 

The two Roughskin Newts were captured and swabbed (both BD negative) in a wetland fen that 

contained 10‐15 small shallow buckbean ponds. Figure A20 is an example of one of these ponds. 

Figures A21 and A22 show the first newt caught, which was a male. The second one was a female. 

Other newts were seen swimming in the ponds. This wetlands complex was upslope of and near the 

junction of the North and West Forks of the Soule River. 

At the pond complex where toad G was found there were a number of tadpoles. There were 50‐100 

tadpoles in the shallows, foreground in Figure A23. There were over 200 at the other end of the pond 

complex where toad G was actually captured (Figure A16). These tadpoles were twice as large as the 

other tadpoles. These tadpole swarms were separated by 85 meters, and belonged to different broods 

(Carstensen 2009, pages 41‐42). There were 7 toadlets caught on 24 Aug 2009 that ranged in size from 

8‐11 mm. On 18 October, two toadlets were caught and measured 14 mm. All toadlets tested Negative 

for BD. 

Tadpoles were also found in a tidal pond on the Delta of the Soule River (Figures A24, A25). There were 

at least 50‐100 tadpoles in the pond. The pond was shallow, approximately 20 meters long, with steep 

sides, and was close to the Portland Canal. Carstensen (2009, pages 35‐36) provides an excellent 

description of the vegetation surrounding this pond. There were 10 toadlets caught on 24 Aug 2009, 

they ranged in size from 13‐19 mm. All toadlets tested Negative for BD. Figure A26 shows an aerial view 

of the tadpole pond and its relationship to other features on the Soule Delta. The Soule River outlet is 

on the left, the pond is in the far background of the scene close to the Portland Canal, and the two large 

Sitka spruce in the center of the scene is where all the Boreal Toad metamorphs were seen in September 

17

2007. There is a third tree, a mountain hemlock, which is difficult to distinguish, and is the closest tree 

to the camera sighting. 

Note the snag extending over the pond and the large and smaller snags in the background in Figure A25. 

Figures A27 and A29 show the pond completely inundated by the high tide. Note that the snag that was 

over the pond is now suspended in the tidal water over the pond. Note also, the large and smaller snags 

in the background. Compare Figures A27 and A28 with Figure A25. 

Figure A5 


18




19


Figure A15 



20




21


Water Chemistry 

A water sample of the Delta tadpole pond was taken on 16 July 2009, before the pond was completely 

inundated by the high Spring Tide (Figure A24). The water in the pond was approximately four inches 

deep at this time. Another water sample was taken on 27 July, after the pond was flooded and the tidal 

water from the Portland Canal was receding (Figure A29). The water in the pond at this time was 

approximately two feet deep. The results of the water chemistry analysis are presented in Table 6 and 

compared to the water in the Portland Canal just below the pond. 

Pond Water Chemistry 

Pond Water 

BEFORE 

Tidal Flooding 

Pond Water 

AFTER 

Tidal Flooding 

Portland Canal 

Water 

Below Pond 

Date of Water Sample 16 July 2009 27 July 2009 27 July 2009 

Specific Conductance 

(μmhos/cm) 

3.5 

2.9 3.9 

Total Suspended Solids 

(mg/l) 

7.0 

12.0 16.0 

Total Dissolved Solids 

(mg/l) 

1760 1370 1900 

Turbidity 

(NTU) 

0.59 2.5 8.8 

Alkalinity 

(mg/l) 

31.8 33.7 29.9 

pH 

6.1 6.5 6.3 

Ammonia 

(mg/l) 

0.054 not detectable not detectable 

Nitrogen 

(NO2/NO3) 

not detectable ‐‐‐‐‐‐ ‐‐‐‐‐‐ 

Total Phosphorus 

(mg/l) 

0.17 

‐‐‐‐‐‐ ‐‐‐‐‐‐ 

Dissolved Organic 

Carbon (mg/l) 

6.3 

‐‐‐‐‐‐ ‐‐‐‐‐‐ 

Table 6. Water Chemistry of Delta Tadpole Pond. 

22

The water in the pond on 16 July before it was flooded was approximately four inches deep. The water 

in the pond was approximately two feet deep on 27 July, after it was flooded by the Spring Tide. Alaska 

drinking water standards specify less that 500 mg/l Total Dissolved Solids, and less than 1000 mg/l for 

irrigation and stock watering. 

The specific conductance of both the pond and canal waters were surprisingly very low, indicating the 

very strong influence of the pure glacial melt water of the Soule River. Correspondingly, note that the 

pH ranged from 6.1‐6.5, also confirming that the water chemistry suggested glacial melt water and not 

marine. The approximate pH of the oceans is 8.1, but drops accordingly in estuaries and at river 

discharges. The pH of pure rainwater is typically 5.6‐5.9 (less than 5.6 is considered “acid rain”), because 

dissolved carbon dioxide makes it slightly acidic. Decaying vegetation produces humic acids, which can 

further lower the pH of ponds. Sphagnum moss exchanges cations with soils producing acidic 

conditions. However, if there is a great deal of aquatic vegetation in ponds, the pH can change 

dramatically over a 24 hour cycle, as active photosynthesis takes up CO2 by day (increasing pH), and 

respiration at night releases CO2 (decreasing pH). 

Note that the pond water was clear (low turbidity) before the flooding (Figure A24, Table 6), but turbid 

after flooding (Figure A29, Table 6). The water in Portland Canal was very turbid, because of the 

abundance of glacial flour in the Soule River. Glacial flour is the fine white silt and clay ground by the 

glacier from the granite bedrock. The suspended solids in the water samples, glacially ground silts, were 

high and exactly paralleled the turbidity. The total dissolved solids were extremely high in all water 

samples, again as expected for a river formed by an active glacier. These solids were approximately 

three times those permitted for Alaska drinking water standards. The high dissolved solids in the pond 

water before flooding were probably due to the concentration of minerals as pond water gradually 

evaporated. The ammonia concentration of 0.054 mg/l in the pond water before flooding may appear 

low, but even trace amounts can stress sensitive organisms. The presence of ammonia in pond water 

indicates the breakdown of proteins from decay or organism excretion without adequate bacterial 

transformation to nitrate. 

Additional field work was conducted in the Soule River Watershed in September and November 2009. 

This presented the opportunity to survey Boreal Toad metamorphs for BD infection at the Soule delta 

pond. In early September, 17 newly transformed metamorphs were swabbed and sent to Pisces 

Molecular for BD analysis. The mid‐November survey yielded two additional metamorphs. All 19 Boreal 

Toad metamorphs tested negative for BD infection. 

The complete Boreal Toad observation data for 2007‐2009 are presented in Table 7. The 19 

metamorphs discussed above were not included in this table. 

23

Year Dates in 

the Field 

Field 

Days 

Observers Observer 

Effort 

Boreal Toads Observed 

in the Field 

Adult Metamorph Larvae 

2007 8‐14 

September 

7 3 21 0 >30 0 

2008 21 July – 

5 August 

16 3 48 3 0 0 

2009 14‐29 July 6 & 2 & 44 6 0 3 

16 2 

Table 7. Boreal Toads (Anaxyrus boreas boreas) Observed in the Field, 2007‐2009. 

Most observations were opportunistic while collecting a wide variety of ecological data and searching 

for wildlife. Habitats included: montane conifer forest, riverine and lacustrine riparian, ponds and 

wetlands complexes, seeps, muskeg, small streams, and river delta brackish marsh. Intense searches 

were made for amphibians when ponds and wetlands were encountered. 

Observer Effort = field days X number of observers. 

All Metamorphs were very similar in size and in the same location, suggesting that they were from a 

single egg deposition. 

Larvae = number of ponds or sections of pond complexes where tadpole clusters were observed. 

Over the three years of field work in a very wide range of habitats throughout the Soule River 

Watershed, 13 Boreal Toad observations were made at an effort of 113 observer‐days. That translates 

to 8.7 observer‐days for each adult Boreal Toad, tadpole or metamorph cluster observation in the Soule 

River Watershed. 

Discussion 

Amphibians are closely ecologically dependent on and linked to their evolved environments. This 

represents a double‐edged sword for amphibian populations. They are ecological indicators or sentinels 

of environmental conditions, but also at the same time, they are highly susceptible to environmental 

changes and habitat degradation. Besides their required environmental template for moisture, 

temperature, and substrate parameters; most species also require habitat mosaics to complete their life 

history requirements, specific breeding sites for egg deposition and larval (tadpole) development. On 

top of these environmental constraints, amphibians have poor dispersal ability, while many populations 

and even entire species have very limited geographic ranges. Therefore, the innate ecology of 

amphibians makes them particularly susceptible to habitat destruction and degradation, pollution, and 

predation. Importantly, amphibians are particularly sensitive to climate change because of: demanding 

physiological needs, habitat and dispersal needs for three stages of life history for most species, and 

close ecological relationship to weather‐its variability‐and predictability. Amphibians are usually very 

difficult to monitor for population trends, because of their innate patterns of boom and bust breeding 

cycles; a direct selection pressure and response to local environmental variability, such as weather 

extremes. 

24

Habitat destruction, pollution, and predation or competition from introduced exotic species (e.g., 

Bullfrogs (Lithobates catesbeianus), trout stocking in fishless lakes) has long been recognized as prime 

drivers in amphibian population declines. A variety of pathogens have also been identified in amphibian 

mortality, including: fungi, bacteria, viruses, protozoans, and occasionally parasites. Rapid major die‐offs 

of anuran populations associated with pristine habitats in the mountains of Central America, rainforests 

of eastern Australia, and the southern and central Rocky Mountains of the United States, signaled 

research and additional surveys. 

Chytrids are the most primitive fungi known, very widely distributed, and have been around for over 350 

million years. They include terrestrial and freshwater saprophytes (decay organisms) that break down 

keratin, chitin, cellulose, and other complex tough molecules and cellular tissue. Therefore, evolution 

has long ago provided them with the tools to break down epidermal keratinized tissues (i.e., 

chytridiomycosis). BD, the species linked to amphibian declines, has been found in the water, 

sediments, and rocks of aquatic habitats (Kirshtein et al. 2007, Walker et al. 2007). Interestingly, BD 

zoospores were not detected in water and sediment samples from high elevation lakes in the Rocky 

Mountains of Montana and Colorado where amphibians were absent, but in the same region where BD 

infected amphibians were found at lower elevations (Hossack et al. 2009). 

A single species of chytrid fungus, (Batrachochytrium dendrobatidis) (BD), was identified and linked with 

amphibian declines from local to global scales. This pathogen was identified as either solely responsible 

for at least some global population declines, or a cofactor in the declines (See Introduction and 

Background). BD was implicated in the three major global areas identified above where anuran 

population declines have been most severe. However, BD occurrences in eastern Canada, and 

northeastern and southeastern United States have not been associated with resulting amphibian 

declines (Ouellet et al. 2005, Longcore et al. 2007, Rothermel et al. 2008). Many BD infected amphibian 

populations survive initial declines and remain viable, despite persistent BD infection (Retallick et al. 

2004, Briggs et al. 2005). 

An interesting characteristic of BD is that it is most pathogenic at lower temperatures (Berger et al. 

2004). Individuals infected with BD and demonstrating clinical symptoms recovered from the infection 

when subjected to higher temperatures (Woodhams et al. 2003, Retallick and Miera 2007). Attempts 

have been made to implicate climate change for optimizing the ideal environmental parameters for BD, 

and thus increase its virulence to amphibian populations (Thomas et al. 2004, Bosch et al. 2007), 

especially in the montane Neotropics (Pounds et al. 2006), but this hypothesis remains controversial. 

Recent research suggests that the temperature dependency of amphibian host response to infection by 

BD may be influenced by climate change (Ribas et al. 2009). 

Complicating matters, it appears that there is a great deal of variation in the severity of BD infection and 

subsequent mortality in anuran populations or species. This can be attributed to a number of non‐ 

exclusive factors. Species or populations innately vary in their susceptibility to BD (Blaustein et al. 

2005b, Woodhams et al. 2007). There are different strains of BD that vary in their lethality (Berger et al. 

2005b, Retallick and Miera 2007, Fisher et al. 2009, James et al. 2009). There are environmental 

parameters that enhance the virility of BD (Pounds et al. 2006, Ribas et al. 2009). There are additional 

stressors that weaken or make individuals more susceptible to BD infection. BD was often theorized as 

the agent delivering the final blow to a population already stressed by habitat degradation, drought, 

pollution, acidic deposition, or excess UV‐radiation (Bosch et al. 2001, Blaustein and Kiesecker 2002, 

Blaustein et al. 2003, 2005b). Species specific behavior such as microhabitat selection or basking 

requirements may increase susceptibility to BD infections (Lips et al. 2003, Rowley and Alford 2007). 

25

Skin peptide defenses (Woodhams et al. 2007) and skin microbes (Harris et al. 2009) protect some 

species from BD infections or mortality. 

Bullfrogs are frequently identified as reservoirs and carriers of BD, and infect more susceptible species or 

populations (Mazzoni et al. 2003, Daszak et al. 2004, Hanselmann et al. 2004, Blaustein et al. 2005b, 

Garner et al. 2006, Pearl et al. 2007). Bullfrogs have been widely introduced or they escaped into many 

habitats in many parts of the world, including the western United States and southwestern Canada. The 

Bullfrog does not occur in Southeast Alaska. Although Bullfrogs and their larvae are typically considered 

predators on or competitors with native anurans, they have not been appreciated by natural resource 

managers as carriers of BD and the decimation of native amphibian communities. The Northern Leopard 

Frog (Lithobates pipiens) has also been identified as a reservoir and carrier of BD (Woodhams et al. 

2008) 

Blaustein et al. (2005b) found that Boreal Toad tadpoles were the most susceptible to BD mortality out 

of the four species tested. Mortality of tadpoles to BD appears to be primarily from toxins produced by 

the fungus. The researchers concluded that the tadpoles of all four species (Boreal Toad, Bullfrog, 

Pacific Chorus Frog, Cascades Frog) could be carriers of BD to infect other anurans. 

BD is a chytrid fungus that is phylogenetically distinct and the only known chytrid that parasitizes 

vertebrates (see Chytrid Fungus section). These data, along with genetic analysis, have suggested that 

BD has only recently evolved, and spread rapidly across the globe (Morehouse et al. 2003, Rachowicz et 

al. 2005, Morgan et al. 2007). James et al. (2009) recently reported that the BD amphibian epidemic is 

the result of a recent emergence of a single successful invasive diploid lineage. 

Boreal Toad populations suffered dramatic and widespread population declines and local extinctions 

throughout the central and southern Rocky Mountains, since the 1970s. Many of the most closely 

monitored populations were in pristine areas (e.g., Rocky Mountain National Park). Boreal Toads also 

declined in the northern Rockies, but not to the severe extent as in more southern portions of their 

range. The major agent appears to be the chytrid fungus Batrachochytrium dendrobatidis (BD), although 

many causes have been proposed, alone or as cofactors with BD and other pathogens. Possibly, Boreal 

Toads, or their southern populations at least, are unusually susceptible to this pathogen. 

Ouellet et al. (2005) in their seminal study documented that 81 out of 295 Bullfrogs (27%) collected 

between 1954‐1999 in the United States and Canada were infected with a chytrid fungus, presumably 

BD. Most or almost all of these were from the eastern range of the species. They concluded that chytrid 

infections were widespread and naturally occurring in eastern North American anuran populations, and 

no single cause could explain population declines. 

The distribution of the Boreal species is very extensive; from northeast British Columbia, eastward to 

north of Lake Superior and the western extreme of Indiana, and south to Arizona, New Mexico, and 

Missouri, with a disjunct population in extreme southern Ontario and Quebec. The Midland species has 

a much smaller range, and is found just to the south and east of the Boreal species. 

The Wood Frog has the largest range of any North American amphibian: found in northeastern, the 

Appalachians, and the upper Midwest of the United States; throughout much of Canada; most of Alaska 

to the north slope; and in three small relict populations in the western United States, extreme northern 

26

Idaho, northern Wyoming, and southern Wyoming and adjacent northern Colorado (Stebbins 1962, 

2003, MacDonald 2003). 

Therefore, at least four species of western North America anurans are potential reservoirs and carriers 

of BD. The Bullfrog appears to be doing very well in both its native and introduced range, many 

populations of the Boreal Chorus Frog are in decline, and all species of leopard frogs (at least seven 

species are currently recognized) are doing poorly, while the status of the Wood Frog is variable and 

unclear (Lannoo 1998, 2005). 

Boreal Toads are apparently widespread and secure in British Columbia and Alberta. The main concern 

for Canadian Boreal Toads is in south‐coastal British Columbia and adjacent Vancouver Island, where 

human population increases and associated infrastructure and pollution are taking their toll. Boreal 

Toads were historically widespread and abundant on southern Vancouver Island in the 1970s. However, 

this species has apparently gone extinct at an extensive and undisturbed wetland, Jordon Meadows, 

while Northern Red‐legged and Pacific Chorus Frogs, Rough skinned Newts, and Northwestern 

Salamanders are all doing well at this site. 

MacDonald (2003) reported that Boreal Toads “are common and widespread on the mainland and 

islands of Southeast Alaska”. There are 70 museum specimen records in Southeast Alaska (MacDonald 

and Cook 2007). However, the records are primarily along the coast and near settlements. Records 

near the British Columbia border and interior, especially in the southeastern portion of Southeast Alaska 

are absent, because of the lack of surveys. Only five records are documented in the general 

southeastern region of Southeast Alaska, none of them in the Soule River Watershed area. 

There is anecdotal evidence provided by long‐time residents in the Skagway area of northern Southeast 

Alaska that Boreal Toads were much more common 20 years ago compared to recent times. A retired 

National Park Service trail crew leader recalled that recent metamorph toads were so abundant during 

summers that thousands of them blanked portions of trails in Klondike Gold Rush National Historical 

Park, and it was impossible to avoid stepping on them. The rumored and perceived declines of Boreal 

Toads at the Park initiated surveys in 2003. Intensive surveys over two summers at 39 potential 

breeding sites, found tadpoles in only six of the sites. 

The first northernmost record for chytrid fungus was from northeastern British Columbia in August 

2000. This was a single Boreal Toad with a prominent mid‐dorsal cutaneous ulcer. The first documented 

occurrence of chytrid fungus (BD) in Alaska was found in a dead subadult male Wood Frog near a pond 

on the Kenai National Wildlife Refuge, Kenai Peninsula, on 25 July 2002. The specimen exhibited 

mycotic hyperkeratotic epidermitis due to infection by BD. 

Dramatic mortality in amphibian populations blamed on chytrid fungus (BD) infections in the United 

States, and indeed globally, along with these two pathogenic cases, motivated amphibian surveys in 

Alaska and western Canada in 2005. These data are summarized in Table 8. 

Boreal Toads Tested for Chytrid Fungus, Batrachochytrium dendrobatidis 

Area Years Number BD positive % BD positive 

NW BC & 

SE Yukon 

2007‐2008 31 18 58 

Skagway, AK 2005‐2006 97 29 30 

27

Area 

Admiralty 

Island 

Prince of Wales 

Island 

South Vancouver 

Island 

Southwest 

BC 

Soule Watershed 

(This Study) 

2005‐2006 27 0 0 

2005‐2006 57 21 37 

2005‐2006 11 0 0 

Pub. in 2009 32 9 28 

2009 6 2 33 

TOTAL ‐‐‐‐‐‐ 261 79 30 

Wood Frogs Tested for Chytrid Fungus, Batrachochytrium dendrobatidis 

Area Years Number BD positive % BD positive 

*Danali 

National Park 

2006 30 0 0 

*Alaska, 3 

Wildlife Refuges 

2006 48 7 15 

NW BC & 

SE Yukon 

2005‐2006 7 6 86 

Skagway, AK 

Area 

2005‐2006 2 0 0 

TOTAL ‐‐‐‐‐‐ 87 13 15 

Table 8. Recent MajorAmphibian Surveys for Chytrid Fungus (Batrachochytrium dendrobatidis) (BD) in 

Alaska and Western Canada. 

The upper table is for Boreal Toads (Anaxyrus boreas boreas), and the lower table is for Wood Frogs 

(Lithobates sylvaticus). BC = British Columbia. No date was given for the southwest British Columbia 

site, but the data were published in 2009. Asterisk identifies sites where the only amphibian species is 

the Wood Frog. Twenty‐two additional amphibians of four species were also found at these sampled 

areas, and two of these tested positive for BD. Two of 10 Northern Red‐legged Frogs (Rana aurora) 

tested positive for BD in southern Vancouver Island. See the Results section for more details and 

literature citations. 

The samples of Table 8 may appear large, and they are useful for an overall assessment. However, Table 

8 combines the data from many individual sampling sites over very large areas. The Results section and 

even the original literature need to be consulted for additional and specific details on the samples in the 

areas identified in the table. Out of the nine general areas where major amphibian surveys for BD were 

conducted, only two areas were negative for BD infection, Admiralty Island and Denali National Park. 

The overall Boreal Toad infection rate for BD was 30 percent. Interestingly, this was the approximate 

infection rate in four of seven areas where this species was tested: southwest British Columbia, Prince of 

Wales Island, Skagway area, and Soule River Watershed. Wood frogs were infected with BD at half the 

rate of Boreal Toads. Boreal Toads and Wood Frogs from 11 sites in northwest British Columbia and a 

28

sample from southeastern Yukon were highly infected with BD. There was a general trend for more 

remote or wilderness collecting sites to have fewer BD infections, while more accessible sites could be 

heavily infected or not infected with BD. However, even remote sites were not free from BD. 

Interestingly, in all the surveys reported in Table 8, BD infected amphibians almost never exhibited 

chytridiomycosis, and dead individuals were not observed. In other words, BD infected individuals had 

no apparent external pathology, such as epidermal lesions or reddening of the ventral skin. In BD 

pathology, the ventral skin in the pelvic patch area and hind limb digits show epidermal lesions with mild 

to severe hyperkeratosis. Additionally, the authors of the reports often made the observation that 

infected individuals were active and did not appear sick or morbid. BD infected individuals appeared 

and behaved indistinguishable from BD negative individuals. The two toads from the Soule Watershed 

that were “very strongly” infected with BD (ID A, Figure A5) and “strongly” infected (ID E, Figure A6) did 

not appear different or behave differently than the four toads that tested BD negative (D, Figure A4; F, 

Figure A12; G, Figure A15; B, Figure A17). All BD positive and BD negative toads were active and did not 

exhibit any lethargic behavior. 

The moldy toad carcass, in active decay and covered with fungus, tested negative for BD (ID C, Figure 

A7). This was of interest, because chytrid fungi evolved as saprophytes that break down keratin, chitin, 

and other tough tissue. 

The absence of observable pathology in BD infected Boreal Toads in the Soule Watershed is consistent 

with all the other amphibian surveys in Alaska and western Canada. Additionally, Soule Watershed 

toads had the same infection rate as the large regional sample (Table 8). Interestingly, out of the six 

toads tested for BD, the two that were infected were the individuals that were the farthest separated in 

the Soule Watershed landscape (toads A and E). Toad F was not infected with BD, and was found in 

proximity to strongly BD infected toad E (Table 5). All of the 19 metamorphs from the Soule delta pond 

tested negative for BD. This is also comparable to other studies, where metamorphs and larvae anurans 

typically have much lower BD infection rates than adults. 

The Soule Watershed is considered remote wilderness and not visited by humans. BD has been 

documented in remote, wilderness, and pristine landscapes in Alaska and western Canada. However, BD 

infection rates were much lower in these remote and inaccessible settings when compared to developed 

areas and road accessible sites. Reeves et al. (2008) found that road accessible sites in Alaskan National 

Wildlife Refuges positively correlated with skeletal abnormalities in Wood Frogs. Some of the highest 

reported abnormality rates in published literature. 

Extensive ecological field investigations and wildlife surveys were conducted in the Soule River 

Watershed from 2007 to 2009. Most wildlife, including amphibian, observations were opportunistic 

while collecting a wide variety of ecological data on the North and West Forks and the main stem of the 

Soule River, at Noname Lake, and at the Soule delta on Portland Canal. Habitats included: montane 

conifer forest, riverine and lacustrine riparian, ponds and wetlands complexes, seeps, muskeg, river 

channels and small streams, and river delta brackish marsh. Intense searches for amphibians were 

conducted in all years at ponds, wetlands, and riparian habitats, but especially 14‐19 July 2009. 

Over the three years of field work in a very wide range of habitats throughout the Soule River 

Watershed, 13 Boreal Toad observations were made at an effort of 113 observer‐days. That translates 

to 8.7 observer‐days for each adult Boreal Toad, tadpole or metamorph cluster observation in the Soule 

River Watershed. Many intense searches were conducted in excellent Boreal Toad habitat, including 

29

ponds and wetlands for tadpoles. This represents an extremely low encounter rate for Boreal Toads, 

indeed any amphibian species. Amphibian surveys were particularly intense 14‐19 July 2009 when 

individuals were swabbed for chytrid fungus. Even during this time period, when a great deal of search 

efforts were in a variety of wetlands, including beaver ponds, fens, brackish marsh, and riparian habitats, 

the encounter rate was still poor at 2.7 observer‐days for each adult Boreal Toad or tadpole cluster 

observation. The searched wetlands, beaver ponds, and fens represented excellent amphibian habitats 

(O’Clair et al.1997, Carstensen 2009). 

The scarcity of Boreal Toads parallels the scarcity of other amphibians and mammals in the Soule 

Watershed. The evidence of rarity is based on visual sightings, the lack of tracks in muddy or sandy soils, 

and the lack of other signs of presence. Approximately, 10 Roughskin Newts were seen in the 2009 

season, and on at least five occasions a frog was seen that rapidly disappeared into dense litter or grass 

and could not be located, despite significant efforts. The general color and litter‐disappearing behavior 

strongly suggested Wood Frogs. The habitats included: North Fork riparian floodplain, a rocky ridge 

above the main stem of the Soule where there are small pockets of water, and the Soule delta marsh. 

The only other potential frog in the Soule Watershed is the Columbia Spotted Frog (Rana luteiventris). 

This species has not been observed in the Soule Watershed, and is typically found closer to aquatic 

habitats than the Wood Frog. We have found this species to be easily observed and captured in pond 

and river habitats, so it is unlikely that our unknown frog is this species. 

The steep and very rugged habitat, deep winter snows, up to 20‐30 feet deep covering the landscape, 

and relatively recent retreat from glacial influences, may explain the general lack of amphibians and 

mammals. Because of the deep winter snowfall, the snow‐free season may be short in the deep valleys 

of the Soule Watershed. Anuran adults or metamorphs could have poor survivorship or dispersal 

potential in this landscape. The short snow‐free season may be particularly difficult for recently 

transformed metamorphs that do not have sufficient time to grow and accumulate body fat for their 

extensive winter hibernation. 

The low population densities of Boreal Toads in some parts of their northern distribution, but apparently 

not in other parts, remain an open mystery. The general consensus is that Boreal Toad populations have 

significantly declined since the 1970s throughout their entire range. But most of the evidence is 

anecdotal for their northern populations, where their habitat consists of huge remote landscapes. By 

current estimates, approximately a third of northern Boreal Toads are infected with BD, and there is a 

high variability of infection rate among populations. Complicating the logic is that northern BD infected 

toads appear asymptotic, and apparent declines and actual rarity occur in both developing areas and 

remote pristine wilderness. Climate change, both current and predicted, does not appear to be a 

significant factor in these northern populations. The risks of BD from anuran reservoirs and carriers are 

not a concern in these northern low diversity amphibian communities, as the alien Bullfrog has been in 

the western United States and southwestern Canada. However, the Wood Frog may be a potential 

carrier of BD. 

A priority among federal, Alaska, and Canadian agencies is the planning of additional monitoring, but 

statistically valid surveys of extensive, remote, and difficult to access landscapes, especially for rare or 

becoming rarer species, are challenging both technically and economically. There is still a great deal 

to learn concerning BD epidemiology. The final appraisal on a comprehensive assessment of the 

detailed causes for amphibian global population declines and species extinctions, and the role that BD 

plays remain to be settled (Collins and Crump 2009, James et al. 2009, Rosenblum et al. 2010). 

30

Discussion Summary 

Documentation of amphibian species in the Soule River Watershed are based on 123 Observer‐Field‐ 

Days in 2007‐2009, while conducting a wide variety of ecological field investigations at the watershed, 

the delta, and Portland Canal (Table 9). Most of these observations were opportunistic (see Methods). 

Potential amphibian species in the watershed are based on museum specimens and species 

documentations for Southeast Alaska from MacDonald and Cook (2007). Amphibians from MacDonald 

and Cook refer to verified specimen records in southern Southeast Alaska, south of Stikine River, but not 

including Prince of Wales Island. Additional amphibian distribution data are from Nussbaum et al. 

(1983), Green and Campbell (1984), Stebbins (1985, 2003), Corkran and Thoms (1996), and MacDonald 

(2003). English and scientific nomenclature is from the Center for North American Herpetology 

CNAH (2010). 

Methods 

Vertebrate documentations were opportunistic while in the field collecting a wide variety of ecological 

data. Nevertheless, several more intensive vertebrate surveys were conducted. Intense amphibian 

searches were conducted in all years at ponds, wetlands, and riparian habitats, but especially 14‐19 July 

2009, when we conducted a survey for amphibian chytrid fungus. Chytrid fungus infections have been 

implicated worldwide in amphibian population declines. A great deal of time was spent looking for birds 

and large mammals, and listening for bird territorial singing. This included extensive scanning with 

binoculars: mountain slopes, ridges, boulder outcrops, talus slopes, forest canopies, wetlands, beaver 

ponds, muskeg, subalpine and alpine zones, river and lake shores, and habitat edges. This was 

particularly the case when camping along the North Fork, at No Name Lake, and on the Soule Delta. 

During all of these efforts we were on the lookout for toads, frogs and newts. 

Our total field effort is presented in Table 9. The entire field efforts in 2007 and summer 2008 were 

conducted while camping in the field. This dramatically increased our early morning, evening, and 

nighttime observations. A total of 123 observer‐days were spent in the field: 

Spring 2008 6 observer days 

Summer 2008‐2009 96 observer days 

Fall 2007 21 observer days 

Survey times are heavily biased for the summer. Although the spring survey season was short and the 

weather was poor, a number of migratory bird species and even nesting species were documented. The 

major time for singing territorial male birds is late May through June, so we missed the major activity of 

these species. Nevertheless, we documented most of the breeding birds of the watershed. 

31

Year Dates 

in the Field 

Field 

Days 

Total 

Observers 

Observer 


2007 8‐14 

September 

7 3 21 

2008 14‐16 

May 

3 2 6 

2008 21 July – 

5 August 

16 3 48 

2009 14‐21 July 8 & 2 & 48 

14‐29 July 16 

2 

TOTAL 49 12 123 

Table 9. Total Field Effort at Soule River Watershed, 2007‐2009. 


for wildlife. Observer Effort = field days X number of observers, summed by individual field seasons. 

The status of amphibian species in the Soule River Watershed is as follows: 

Documented Amphibians 

Boreal Toad 

Northern Roughskin Newt 

Unidentified Frog: Has the appearance and behavior of wood frogs, but Columbia spotted frogs 

are more likely, based on the geographical distribution of the limited specimens from MacDonald 

and Cook (2007). 

Unknown Potential Amphibians 

Wood Frog 

Columbia Spotted Frog 

Northwestern Salamander 

Eastern Long‐toed Salamander 

Unlikely Amphibians 

Northern Red‐legged Frog 

Pacific Chorus Frog 

Pacific Tailed Frog 

32

Documented Amphibians 

Boreal Toad (Anaxyrus boreas boreas) 

Local Range: British Columbia; Southeast Alaska; disjunctive and coastal northward 

MacDonald and Cook (2007): >10; well distributed south of Skagway, mainly coastal and islands 

(see below) 

Elevation Range: Sea level to 2250m 

Habitat: 

A terrestrial and wetlands species found in humid open forests with moderate to dense undergrowth, 

including old fields and meadows, often near surface water. Boreal toads breed in permanent or 

temporary quiet pools of streams and sloughs, wetlands, lakes and ponds; including brackish pools. The 

use of at least occasional brackish pools for breeding is very unusual for North American frogs and toads. 

The species tolerance for brackish and even sea water have enabled it to disperse widely in Southeast 

Alaska, including the colonization of islands. 

Boreal Toads are widespread in Southeast Alaska, and range northward along the coast to Prince William 

Sound, including Montague and Hawkins Islands; with the edge of their range a short distance north to 

the Tasnuna River (a tributary of the Copper River) and west to the Columbia Glacier (MacDonald 2003). 

MacDonald reported that Boreal Toads “are common and widespread on the mainland and islands of 

Southeast Alaska”. Boreal Toad records are certainly widely distributed throughout Southeast Alaska 

(MacDonald 2003, MacDonald and Cook 2007). There are 70 museum specimen records in Southeast 

Alaska documented by geographic location (usually including latitude and longitude) and a distribution 

map in MacDonald and Cook (2007, pages 127‐128), including records for 30 islands in the archipelago. 

The records are particularly prevalent along the coast and near settlements. Records near the British 

Columbia border and interior, especially in the southeastern portion of Southeast Alaska are absent, 

because of the lack of surveys. 

Only five records are documented in the general southeastern region of Southeast Alaska, none of them 

in the Soule River Watershed area. The number of museum specimens are in parenthesis. 

North West 

Latitude Longitude 

Hyder (1) 55.9200 130.0200 

Hyder Area (1) ‐‐‐‐ ‐‐‐‐ 

Salmon River, at mouth of Texas River 

Approx. 40 miles west of Hyder (1) 56.0269 130.9844 

Approx 5 miles east of Behm Canal 

Approx. 25 miles north of Chickamin Bay 

Boca de Quadra (3) 55.2000 130.4700 


of Portland Canal inlet 

33

Smeaton Bay (1) 55.2800 130.6300 

Head of Blackwell Arm, 

just north of Boca de Quadra 


of Portland Canal inlet 

With the exception of the Hyder sites, the other three sites are west of the mountains where the Soule 

River Watershed originates, and the Soule River flows east to the Portland Canal. 

Boreal toad Southeast Alaska populations, as well as in other parts of their range, are experiencing sharp 

declines. 


The complete boreal toad observation data for 2007‐2009 are presented in Table 10. 

Year Dates in 

the Field 

Field 

Days 

Observers Observer 


Boreal Toads Observed 

in the Field 

Adult Metamorph Larvae 

2007 8‐14 7 3 21 0 1 cluster 0 

September 

(>30) 

2008 21 July – 

5 August 

16 3 48 3 0 0 

2009 14‐19 July 6 & 2 & 44 6 0 3 

14‐29 July 16 2 

TOTAL 45 10 113 9 1 3 

Table 10. Boreal Toads (Anaxyrus boreas boreas) Observed in the Field, 2007‐2009. 


for wildlife. Habitats included: montane conifer forest, riverine and lacustrine riparian, ponds and 

wetlands complexes, seeps, muskeg, small streams, and river delta brackish marsh. Intense searches 

were made for amphibians when ponds and wetlands were encountered. 

Observer Effort = field days X number of observers. 

All Metamorphs were very similar in size and in the same location, suggesting that they were from a 

single egg deposition. Larvae = number of ponds or sections of pond complexes where tadpole clusters 

were observed. 

Boreal toads are diurnal in Southeast Alaska, especially on rainy days, and tadpoles are present in ponds 

during July and August (MacDonald 2003). At Juneau Alaska, Boreal Toads deposit eggs in late April – 

early May, tadpoles are present mid May – early July, and metamorphs are present late July – early 

August (Pyare et al. 2004). Juneau is located approximately 230 miles northwest of the Soule River 

Watershed, but possesses a more maritime climate, so these dates are probably extended at the Soule. 

34

Over the three years of field work, mostly during July, including many rainy days, in a very wide range of 

habitats throughout the Soule River Watershed, only 13 Boreal Toad observations were made at an 

effort of 113 Observer‐Days: nine adults, a scattered metamorph clump, and three larval (tadpole) 

clumps. An observation consists of an adult or an independent cluster of larvae (tadpoles) or 

metamorphs. That translates to 8.7 observer‐days for each Boreal Toad adult and tadpole or 

metamorph cluster observation in the Soule River Watershed. 

Many intense searches were conducted in excellent Boreal Toad habitats, including concentrated 

searches in numerous ponds and wetlands for tadpoles. This represents an extremely low encounter 

rate for Boreal Toads, indeed any amphibian species. Admittedly, adult Boreal Toads are difficult to 

observe, because of their excellent camouflage color and pattern, coupled with their behavior to remain 

quiet. Additionally, much of their habitat is rugged, consisting of large downed snags, boulders, rocks, 

and forest or riparian litter. Nevertheless, the extremely low encounter rate for tadpoles is especially 

revealing, because tadpoles should be readily revealed in ponds and wetlands during July, when most of 

our field work and amphibian searches were conducted. Amphibian surveys were particularly intense 

14‐19 July 2009 when individuals were swabbed for chytrid fungus. Even during this time period, when 

a great deal of concentrated search efforts were in a variety of wetlands, including: beaver ponds, fens, 

muskeg and bogs, brackish marsh, and riparian habitats; the encounter rate was still poor at 2.7 

observer‐days for each Boreal Toad adult or tadpole cluster observation. All these wetlands represented 

excellent amphibian habitats (O’Clair et al.1997, Carstensen 2009). 

Our records for Boreal Toads in the Soule River Watershed are the first reported for the southeastern 

interior area of Southeast Alaska, outside of Hyder. 

Locations for Boreal Toads: 

3 adults, July 2008: lower North Fork, east bank, riparian/floodplain 

1 adult, 14 July 2009: middle North Fork, west side, fen wetlands complex 

1 adult, 15 July 2009: lower West Fork, south side, near junction, fen wetlands complex 

1 adult, 15 July 2009: middle Main Stem, west side, mature hemlock forest, above beaver ponds 

2 adults, 18 July 2009: middle Main Stem, west side, fen wetlands complex, downstream of above 

1 adult, 18 July 2009: upper Main Stem, west side, fen wetlands complex 

1 metamorph clump, 12‐14 September 2007: Soule Delta, south side, interior uplift, high grass and 

under spruce canopy. 

1 tadpole clump, 14‐29 July 2009: Soule Delta, small pond on south side of Delta, close to Portland 

Canal, completely flooded over during spring high tides 50‐100 individuals, the tadpoles are slowly 

growing in size, but decreasing in number over the observation period. 

2 tadpole clumps, 18 July 2009: upper Main Stem, west side, fen wetlands complex, two different 

clutches at distant ends of wetlands complex, 50‐100 individuals in one clump, over 200 individuals in 

second clump, and tadpoles twice as large. 

35

Northern Roughskin Newt (Taricha granulosa granulosa) 

Local Range: Coastal British Columbia; Southeast Alaska, as far north as Juneau 

MacDonald and Cook (2007): >10; well distributed south of Juneau, coastal and islands 


Habitat: 

Humid coastal forests to high mountain lakes. Found in and around ponds, lakes, and stream 

backwaters; where there is an abundance of aquatic plants. 

All of the records in MacDonald and Cook (2007) are coastal and on islands. One is at Stikine River 


At least 20 roughskin newts were seen in July 2009. The newts were closely associated with clear water 

ponds, typically with an abundance of buckbean (Menyanthes trifoliata) emergents. The ponds were 

typically in fen wetland complexes. One tannin stained pond was associated with a series of pools on a 

rocky boulder ridge above the Main Stem of the Soule, not far downstream from the junction of the two 

forks on the eastern side. 

Our records for Northern Roughskin Newts in the Soule River Watershed are the first reported for the 

southeastern interior area of Southeast Alaska. 

Locations for Northern Roughskin Newts: 

5 adults, 15 July 2009: lower West Fork, north side, just north of confluence, ponds in fen wetlands 

complex. 

15 adults, 15‐29 July 2009: middle Main Stem, east side, ponds in extensive fen wetlands complexes. 

Unidentified Frog 

Frogs were seen on at least five occasions. The individuals rapidly disappeared into dense litter or grass 

and could not be located, despite significant efforts. The general color and litter‐disappearing behavior 

strongly suggested wood frogs. The habitats where the frogs were observed included: lower North Fork, 

east side, riparian floodplain, a boulder‐rocky ridge on the east side of the middle Main Stem where 

there are small pockets of water, and the Soule Delta grassy marsh. There are at least six wood frog 

museum records for the Stikine River drainage area, the southernmost documented locality for this 

species in Southeast Alaska (MacDonald and Cook 2007). The Soule Watershed is over a 100 miles 

southeast of this locality. The only other potential frog in the Soule Watershed is the Columbia Spotted 

Frog. We have found this species to be easily observed and captured in pond and river habitats in the 

northwestern United States, so we thought it unlikely that our unknown frog was this species. There are 

four records for this species at Hyder, two at Salmon River and two at Fish Creek (MacDonald and Cook 

2007). There is also a record of two at Unuk River, approximately 40 miles west of Hyder. These records 

are also the southernmost localities for this species. The lack of museum records for these two frog 

species in southern Southeast Alaska appears to represent an actual absence or rarity, because both 

boreal toads and roughskin newts are clearly documented on islands and south coastal areas of 

36

Southeast Alaska, clearly indicating field surveys in these areas (MacDonald and Cook 2007). 

Nevertheless, the interior eastern boundary of Southeast Alaska, outside of the Hyder area, lacks 

museum records for all amphibian species. The unknown frog remains a mystery, acting like a wood 

frog, but closer in range to a documented Columbia spotted frog locality. 

Amphibians with Unknown Status 

Wood Frog (Lithobates sylvaticus) 

Local Range: Widespread in interior Alaska; Southeast Alaska north of Stikine River; 

The Wood Frog is North America’s only amphibian or reptile found in the Arctic Circle 

MacDonald and Cook (2007): 4; all at Stikine River 


Habitat: 

Wood frogs occur in a wide variety of habitats: open forests, meadows, riparian, muskeg, and tundra. 

They are exceptionally cold‐tolerant and active at near freezing temperatures, and they are also drought 

and dehydration tolerant. Wood frogs breed unusually early in the season throughout their range in 

permanent or temporary shallow pools. They hibernate or are dormant during drought under forest, 

meadow, or tundra litter. 

Soule River Watershed: 

Unknown – see above section discussing unidentified frog 

Columbia Spotted Frog (Rana luteiventris) 

Local Range: British Columbia; Southeast Alaska south of Taku River 

MacDonald and Cook (2007): 7; 3 at Stikine River, 3 in vicinity of Hyder 


Habitat: 

This is a riparian species that is closely associated with permanent water: lakes, beaver and muskeg 

ponds, rivers, streams, and fluvial backwaters. Foraging, breeding, and hibernation all take place in 

these habitats. 


Unknown – see above section discussing unidentified frog 

Northwestern Salamander (Ambystoma gracile) 

Local Range: Coastal British Columbia; 2 records for Southeast Alaska 

MacDonald and Cook (2007): 1; Mary Island, southeast of Ketchikan 


37

Habitat: 

Moist forests or open woods; breeding in usually permanent water, but also temporary pools, including 

beaver ponds and stream backwaters; breeds in early to mid‐spring. Highly fossorial, and are primarily 

active nocturnally and after heavy precipitation. 


Unknown 

Eastern Long‐toed Salamander (Ambystoma macrodactylum columbianum) 

Local Range: British Columbia; 4 records for Southeast Alaska 

MacDonald and Cook (2007): 3; 2 Stikine River 


Habitat: 

Moist forests, open woods, and grasslands; broad habitat tolerance; breeding in permanent or 

temporary quiet pools, including beaver ponds, stream backwaters, and wet meadows; breeds in winter 

to early spring. Highly fossorial and are primarily active nocturnally and after heavy precipitation. 


Unknown 

Unlikely Amphibians 

Northern Red‐legged Frog (Rana aurora) 

Local Range: Coastal southwestern British Columbia 

MacDonald and Cook (2007): None; Northeast Chichagof Island, Pavlof Bay drainage, 

Introduced? 


Habitat: 

This is a species of riparian zones of lakes, ponds, and streams; and marshes. It can also be found in 

nearby forests, woodlands, and meadows, especially in wet weather. It prefers dense ground cover, 

aquatic vegetation, and vegetation hanging over water. For breeding, it prefers deep permanent pools 

of quiet or slow‐flowing water. 


Unlikely 

Pacific Chorus Frog (Pseudacris regilla) 

Local Range: Southern British Columbia; 

Introduced to Queen Charlotte Islands 

MacDonald and Cook (2007): 2; Introduced to a muskeg pond near Ward Lake, Revillagigedo Island 

38


Habitat: 

This species inhabits a wide variety of habitats: forests, open woodlands, dense meadows, shrub‐lands, 

even oasis in desert scrub. It prefers high ground cover and is usually close to permanent water: lakes, 

muskeg ponds, streams, springs and oasis. 


Unlikely 

Pacific Tailed Frog (Ascaphus truei) 

Local Range: Coastal British Columbia 

MacDonald and Cook (2007): None; A “watch for” species in southeastern Alaska 

This species has not been documented in Alaska, found in coastal British Columbia close to the Alaska 

border. 


Habitat: 

This is a species adapted to living adjacent to and breeding in fast running mountain streams. Their 

tadpoles have a sucker mouth to live and feed in stream rapids. 


Unlikely 

39

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54

Test samples: 

Appendix A 

PCR Assay Details from Pisces Molecular 

Chytrid Fungus Test Results 

PCR assay for B. dendrobatidis 

Organization: Shipely Group 

Received From: Paul Rusanowski 

Received Date: 7/31/09 

Number of samples: 9 

Type/condition of sample(s): Swabs in ethanol 

Need to be pooled? No 

Comments 

The labels on the tubes were hard to 

read. 

Sample Preparation: 

The liquid in each of the skin swab samples was mixed by pipetting the liquid up and down repeatedly. 

The entire volume of each sample was then transferred into individual microfuge tubes. The tubes were 

spun in a microcentrifuge at ~16,000 x G for 3 minutes. Next, the supernatant was drawn off and 

discarded. Lysis buffer was added to the tubes and any pellet present was resuspended by vortexing. 10 

μg of carrier DNA was added to the lysis buffer. 

Total 

DNA was extracted from all samples using a spin-column DNA purification procedure. 

PCR assay: 

The sample DNA(s) prepared was/were assayed for the presence of the Batrachochytrium dendrobatidis 

ribosomal RNA Intervening Transcribed Sequence (ITS) region by 45 cycle single-round PCR 

amplification using an assay developed by Seanna Annis and modified for greater specificity and 

sensitivity 

at Pisces. 

Each PCR run included the following controls: 

Positive DNA: DNA prepared from a laboratory culture of B. dendrobatidis, Strain JEL 

270, 

kindly provided by Joyce Longcore. This sample was previously 

demonstrated to 

be positive by PCR. The signal from this sample is the standard for a very 

strong positive (+++) signal. 

Negative DNA DNA prepared from an uninfected amphibian. This sample has been 

previously demonstrated as negative (-) by PCR. 

No DNA: H2O in place of template DNA. This reaction remains uncapped during 

addition 

of sample DNA to the test reactions, and serves as a control to detect 

contaminating DNA in the PCR reagents or carryover of positive DNA 

during reaction set-up. 

55

PCR 

Results for the B. dendrobatidis ribosomal RNA ITS region: 

Number of positive (+) samples: 2 

Number of negative (-) samples: 7 

Individual sample results are shown on the following page(s). 

Scoring: +++ = very strong positive signal 

++ = strong positive signal 

+ = positive signal 

w+ = weak positive signal 

- = no signal/below limit of detection 

56

APPENDIX B 

Amphibian Declines, Chytrid Fungus, and Boreal Toads 

Anthony J. Krzysik, Ph.D. 

28 February 2010 

Introduction and Background 

Scientists were seriously concerned with the widespread evidence in the 1970s and 1980s that 

amphibians, especially anurans, were undergoing dramatic population declines from local and regional to 

global scales (Barinaga 1990, Blaustein and Wake 1990, Czechura and Ingram 1990, Phillips 1990, 

Wyman 1990, Tyler 1991, Wake 1991, Hedges 1993, Blaustein et al. 1994c). The class Amphibia 

consists of three orders: salamanders and newts, anurans (frogs, toads, spadefoots), and caecilians 

(Gymnophiona). Caecilians are poorly known tropical legless amphibians with short tails, resembling fat 

earthworms. They are very secretive and primarily subterranean, and their population stability or declines 

are unknown. The rather sudden comprehension of amphibian declines motivated the origination of “The 

Declining Amphibian Populations Task Force” at the First World Congress of Herpetology in England in 

1989. Through this organization a concerted effort was made to assess the status and trends of United 

States and Canadian amphibians (Green 1997, Lannoo 1998, 2005). 

The amphibian population declines continued into the 1990s and new millennium, and the declines were 

often catastrophic and global in scale (Lips 1998, Carey 2000, Houlahan et al. 2000, Young et al. 2001, 

Stuart et al. 2004, Mendelson et al. 2006, Wake and Vredenburg 2008, Collins and Crump 2009). Indeed, 

the current global extinction rate of amphibians, when including species in eminent danger of extinction, 

may range from 25,039 to 45,474 times the background extinction rate of amphibians in the fossil record 

(McCallum 2007). Amphibians are the most endangered taxa of vertebrates (Stuart et al. 2004), and are 

in the dubious position of representing the forerunners in the sixth mass extinction on earth (Leakey and 

Lewin 1995, Novacek 2007, Ward 2007, Avise et al. 2008, Wake and Vredenburg 2008). At least 2468 

(43.2%) amphibian species are experiencing declines, and 1856 (32.5%) are globally threatened, listed on 

IUCN Red List (Stuart et al. 2004). It appears that amphibians represent a major indicator or canary in 

the coalmine for ecosystem assessment and monitoring. 

The proposed reasons for the decline were an equally dramatic laundry list of readily apparent to 

hypothesized causes: habitat destruction and degradation, habitat and landscape fragmentation, water and 

air pollution, pesticides, heavy metals, acidic deposition, deforestation, increased UV radiation, disease 

caused by pathogenic organisms, and introduced species (e.g., Bullfrogs [Lithobates catesbeianus], trout 

stocking in fishless alpine lakes). The well known stratospheric ozone depletion increases the amount of 

ultraviolet radiation striking earth’s surface. The biologically UV of concern is in the 290 to 320 nm, 

UV-B (Blaustein et al. 1994a). Although most of the increase of UV is at Polar Regions, there is 

evidence for increased UV-B radiation in undisturbed temperate latitudes (Blumthaler and Ambach 1990). 

All amphibian common and scientific names have been updated to reflect current taxonomic status 

(CNAH 2010). Therefore, common or scientific names in this report may differ from cited publications. 

Phillips (1994), Alford and Richards (1999), and Collins and Crump (2009) provide comprehensive 

references for all the potential agents implicated or suspected in amphibian declines. 

57

Amphibians, as are all vertebrates, susceptible to a wide range of diseases and individual mortality caused 

by: fungi, viruses, protozoans, bacteria, and macroparasites (e.g., trematodes). However, only the first 

three have been implicated in the widespread declines and extinctions of amphibian populations (Collins 

and Crump 2009). By far the main pathogen identified with amphibian declines and extinctions has been 

the chytrid fungus Batrachochytrium dendrobatidis. Eight viral groups infect amphibians, but only 

iridoviruses are common, and at least eight Ranavirus strains were involved with amphibian epidemics 

(Collins and Crump 2009). See Chytrid Fungus section for more information. 

UV Radiation 

Habitat loss and fragmentation along with pollution were the obvious suspicious culprits for amphibian 

declines. Habitat loss is the greatest threat to amphibians, impacting almost 90% of listed species 

(Mendelson et al. 2006). Excess UV radiation was also a major suspect, because of the global scope of 

the declines, and that the declines were frequently associated with montane habitats. A great deal of 

research, especially in Andy Blaustein’s laboratory, was directed to the effect of UV radiation on 

amphibian eggs, embryos, larvae (tadpoles), and adults (Worrest and Kimeldorf 1976, Blaustein et al. 

1994a, 1997, 1998, 2005a). The eggs of Boreal Toads (see Boreal Toads section) and Cascades Frogs 

(Rana cascadae) are deposited in open water highly exposed to sunlight. Laboratory studies of Boreal 

Toad embryos from the Cascade Mountains of Oregon have increased mortality from UV exposure 

(Worrest and Kimeldorf 1976). Eggs of this species show high mortality at some sites (Blaustein and 

Olson 1991). Boreal Toads and Cascades Frogs both have undergone dramatic declines (Fellers and 

Drost 1993, Blaustein et al. 1994a). 

Subsequent research found the UV issue to be a great deal more complex, contradictory, and suggested 

potential additional interactions with other stressors such as pollution or disease (Corn 1998, Palen et al. 

2002, 2004, Blaustein et al. 2003, 2004, Collins and Crump 2009). The complexity was magnified by the 

distinct possibility of cumulative effects and independent synergistic interactions. 

Pesticides 

The Moutain Yellow-legged Frog (Rana muscosa) was divided into two full species in 2007 (CNAH 

2010). Both species have undergone significant population declines in both distribution and abundance. 

The combined species have lost approximately 99% of their original distribution (Stebbins 2003). The 

Sierra Nevada Yellow-legged Frog (Rana sierrae) is restricted to the Sierra Nevada Mountains north of 

Mather Pass (California Herps 2010a); while the Sierra Madre Yellow-legged Frog (Rana muscosa), with 

a clear relict distribution, is now only found in tiny local isolated populations in the southern Sierras south 

of Mather Pass, and in the San Gabriel, San Bernardino, and San Jacinto Mountains (California Herps 

2010b). It is now extinct on Palomar and Breckenridge Mountains. The Foothill Yellow-legged Frog 

(Rana boylii) and California Red-legged Frog (Rana draytonii) have also suffered dramatic distribution 

and abundance declines. There is strong evidence for pesticides as a major factor in the dramatic declines 

of all these species, but there were often multiple stressors involved (Davidson et al. 2001, 2002, 2007, 

Davidson 2004, Davidson and Knapp 2007). The decline of California Red-Legged Frogs is closely 

associated with upwind borne agrochemicals (Davidson et al. 2001). Pesticides have apparently 

contributed to inhibiting natural immune defenses against chytrid fungus susceptibility. Skin peptide 

defenses were significantly reduced in Foothill Yellow-legged Frogs after sublethal exposure to carbaryl 

(a cholinesterase inhibitor), suggesting that pesticides may inhibit this innate immune defense and 

increase chytrid susceptibility (Davidson et al. 2007). Rachowicz et al. (2006) reported that 96% of 

Moutain Yellow-legged Frogs died in controlled field experiments at chytrid fungus infected sites in the 

Sierra Nevadas of California. They concluded that this pathogen is a severe threat for local extinctions at 

many sites in the Sierras. Additionally, introduction of nonnative rainbow and brook trout into Sierra 

58

Nevada’s fishless alpine lakes over the last 50 years were responsible for a major reduction of native frogs 

(Knapp et al. 2001, 2007). 

Sublethal concentrations of pesticides may also cause unexpected mortality in amphibian communities. 

Relyea and Diecks (2008) reported that a sublethal malathion concentration for amphibians, a globally 

widespread and commonly used insecticide, had a significant impact on the reduction of zooplankton and 

periphyton. The resulting trophic cascade dramatically affected the growth and development of Northern 

Leopard Frog (Lithobates pipiens) larvae, and this species was subjected to higher mortality. Leopard 

Frog tadpoles take longer to develop than the Wood Frog (Lithobates sylvaticus) tadpoles that also 

inhabited the pond. Wood Frogs were not affected, because of their shorter larval period. 

Predation 

Predation by introduced species has always been hypothesized as a major factor in the decline of western 

anurans. The primary culprits have been Bullfrogs and stocking trout into fishless lakes (Hayes and 

Jennings 1986, Fisher and Shaffer 1996, Knapp et al. 2001, 2007). Nevertheless, Jones et al. (1999) 

found that neither brook trout or cutthroat trout would prey on tadpoles. 

Toads are typically assumed to be less susceptible to predation than other native anurans, because of their 

toxic skin secretions. Licht (1968) reported that fish would not eat toad eggs. Experiments demonstrated 

that Boreal Toad skin secretions are unpalatable to fish (Kiesecker et al. 1996). However, Gunzburger 

and Travis (2005) in a review of 142 papers that dealt with unpalatability as a defense against predation 

on amphibian eggs and larvae found that the studies were inconsistent and often the results were 

influenced by experimental method. Several interesting patterns emerged from their review. Eggs and 

hatchlings were more unpalatable than mobile larvae. Temporary water amphibian breeders were more 

palatable to predators than species that breed in perennial waters. Fish and salamanders were more likely 

to find amphibians unpalatable than insect predators. They concluded that unpalatability is rare, but when 

it occurs it is a property of a particular predator-prey system and a life-history stage, and not a speciesspecific 

attribute. 

Kagarise Sherman and Morton (1993) provide an interesting literature review and their own observations 

of avian predation on toads. Three species of corvids were involved in predation on toads in the Boreal 

Toad species group. The Common Raven was implicated in predation on Boreal and Black Toads, Blackbilled 

Magpies also attacked the Black Toad, and Clark’s Nutcracker was responsible for most of the 

attacks on Yosemite Toads, but also California Gulls. Beiswenger (1981) reported another corvid 

predator, Gray Jays feeding on Boreal Toad tadpoles. American Crows have also preyed on toads 

(Brothers 1994). Brewer’s Blackbirds and American Robins have also been documented to feed on 

tadpoles or metamorphs. Probably most of this predation occurs when temporary pools are drying up. 

Pacific Chorus Frogs (Pseudacris regilla) have been observed to feed heavily on California Toad 

(Anaxyrus boreas halophilus) eggs (Wind and Dupuis 2002). Predatory aquatic insects, especially 

hemipterans (e.g., Lethocerus, Notonecta) and diving beetles (Dytiscidae) feed on tadpoles. 

Raccoons and Striped Skunks were suggested as the likely predators on American Toads (Anaxyrus 

americanus) in the eastern United States (Schaaf and Garten 1970, Groves 1980). Additional documented 

predators on Boreal Toads include: garter snakes (Thamnophis sp), Tiger Salamanders (Ambystoma 

mavortium), Red-tailed Hawks, and Raccoons (Pierce 2006). Predators are commonly attracted by the 

presence or activity of humans. This has been appreciated and well-documented for nesting success in 

birds, but has not received attention for amphibian and reptile populations. Residential and agricultural 

development, water management, wastewater treatment, landfills, landscaping, roads, and the creation of 

edges and habitat fragmentation have all attracted predators with resulting impacts on both avian nest 

success and presumably amphibian and reptile populations. Examples of these predators include: 

59

Common Raven, American Crow, Raccoon, Coyote, Mallard, Spotted Sandpiper, jays and additional 

corvids, grackles and blackbirds, foxes, skunks, domestic and feral geese and ducks, and of course cats 

and dogs. 

Population Monitoring Difficulties 

Additionally, researchers who work with amphibians are well aware that many species are “explosive 

breeders”, an evolutionary adaptation to take advantage of optimal environmental conditions, after a 

series of poor reproductive years, because of drought, cold, excess predation, or other unfavorable 

environmental conditions during the breeding season (e.g., Pechmann et al. 1991, Pechmann and Wilbur 

1994). The resulting strong oscillations of local population trends make statistical time-series analysis 

very tenuous. Another population monitoring problem is that many amphibian species exist as 

metapopulations in the landscape. Tracking metapopulations dynamics when conducting local amphibian 

surveys appreciably adds to the uncertainty of assessing the status and trends of populations (Alford and 

Richards 1999). 

Amphibian Declines in Pristine Areas 

Amphibian declines were often associated with anthropogenic local impacts, even on global scales, such 

as: habitat loss and fragmentation, pollution, forest logging, over grazing, extended droughts, and 

competition or predation from exotic species. However, even these still did not completely explain the 

dramatic global amphibian declines, particularly the many well-documented declines in pristine 

landscapes in the United States (Bradford 1991, Carey 1993, Kagarise Sherman and Morton 1993, Drost 

and Fellers 1996, McMenamin et al. 2008); Neotropics (Heyer et al. 1988, Crump et al. 1992, Pounds and 

Crump 1994, Pounds et al. 1997, Lips 1998, Young et al. 2001, Ron et al. 2003, Burrowes et al. 2004); 

and Australia (Czechura and Ingram 1990, Gillespie and Hollis 1996, Laurance et al. 1996). For example, 

considering the data for all global species of amphibians based on their general habitat: 90.3% of forest, 

79.2% of flowing water, and 74.9% of tropical montane habitats represent rapidly declining species where 

suitable habitat remains, and the reasons for the decline are not obvious (data from Stuart et al. 2004, 

Table 1). Concurrently, no statistically significant amphibian declines are known to have occurred with 

savanna (0%), shrublands (6.8%), or marshes/swamps (6.8%) species. 

Climate Change 

Significant ecological changes have been documented for climate change, including predictions for 

biological extinctions (Pounds et al. 1999, Harvell et al. 2002, McLaughlin et al. 2002, Thomas et al. 

2004, Lovejoy and Hannah 2005, Parmesan 2006, Schwartz et al. 2006, Rosenzweig et al. 2008). 

Amphibians are particularly sensitive to climate change because of: demanding physiological needs, three 

stages (at least for most species) of life history environments, multiple habitat mosaics for most species, 

close ecological relationship to weather-its variability-and predictability, and of course poor dispersal 

ability. Climate change has been frequently implicated with amphibian population declines (Pounds and 

Crump 1994, Ovaska 1997, Blaustein et al. 2001, Carey and Alexander 2003, Corn 2003, Daszak et al. 

2005, Pounds et al. 2005, 2006, McMenamin et al. 2008). For a contrasting view, see Alexander and 

Eischeid (2001) for an interesting analysis, where they could not find unusual regional weather directly 

responsible for amphibian declines in Colorado, Puerto Rico. Costa Rica/Panama, and northeast 

Queensland, Australia, but they did not rule out indirect effects. Recent work predicting climate-driven 

shifts for the period 2071-2100 in the distribution of 413 western hemisphere amphibian species identified 

a number of areas of high species turnover (Lawler et al. 2010). The areas of greatest stress for 

amphibians were primarily in the Neotropics, especially in mountainous habitats, but also included the 

Southwest of the United States. These also appear to be the same areas of dramatic current amphibian 

population declines. 

60

Climate change can be implicated in amphibian declines in three general categories. First of all, are 

specific physical and/or chemical environmental changes to the habitat at some portion of amphibian life 

history. This would include: drought, thermal extremes, severe or prolonged storms, and changes in 

aquatic or soil chemistry. Additionally, climate can change the biological environment of species. This 

list can be lengthy, but if the amphibian literature represents any guide, disease and their related 

pathogens would unarguably rank first on the list, particularly chytrid fungus. Nevertheless, even after all 

the current research and experiments, the detailed relationships of climate change to amphibian diseases 

and pathogens are still highly controversial (see next paragraph). Other biological influences include: 

vegetation changes, soil changes, competition and/or predator dynamics, and a wide range of prey 

requirements. Amphibian relationships to their prey are many and include seasonal parameters: life 

history needs such as algae or micro-invertebrates for larvae, prey abundance or diversity, prey taxa and 

their spatial distribution, prey availability, and life history phenology of prey. And finally, climatic 

parameters can affect one or more amphibian life history parameters: behavior, physiology, reproduction, 

development, and phenology. All of these life history attributes affect survivorship, population viability, 

and species persistence. 

The dramatic anuran declines documented in the western United States and the Neotropics were mainly 

montane species. This suggested climate change. The Golden Toad (Incilius [formerly Bufo] periglenes, 

Bufonidae), a mountain cloud forest species with a very small distribution in the Monteverde Cloud 

Forest Preserve of Costa Rica, has often been cited as the first known extinction caused by climate change 

(e.g., Flannery 2005, pp 114-122). However, a good case was made for a strong El Nino effect (Crump et 

al. 1992). Although storms and extreme weather can be amplified in strength and/or frequency by climate 

change (Mann and Kump 2008), the effect of climate change on the natural El Nino and La Nina events 

are not clear and currently a major research question (NCDC 2010). There were also the confounding 

effects of deforestation near the preserve (Nair et al. 2003). Pounds et al. (2008) concluded that the 

Golden Toad was extinct, and the cause was a combination of global warming, chytrid fungus 

(Batrachochytrium dendrobatidis), and airborne pollution, including its restricted range. The Monteverde 

Harlequin Frog (Atelopus varius, Bufonidae) also vanished at the same time with the Golden Toad, and an 

estimated 67% of the approximately 110 species of Neotropical endemic Atelopus followed (La Marca et 

al. 2005). 

The montane Neotropics have provided some of the best evidence for climate change as an important 

driver for biodiversity impacts, and especially, amphibian declines and extinctions. The data are most 

extensive and conclusive for anurans, anoline lizards, and breeding birds; but also include salamanders, 

other lizards, snakes, and tree squirrels (Pounds et al. 2005). Nevertheless, direct evidence for climate 

change as the primary cause of amphibian declines and extinctions has often been elusive and 

controversial. This is because climate change directly affects physical and biological environmental 

attributes that are either critical for amphibian life history or phenology, or affect biotic interactions. 

Precipitation, moisture, snow cover, and evolved optimal temperatures are critical for amphibian 

population viability. Competition, predation, parasites, and disease pathogens are critical biotic 

interactions that are certainly driven by changing physical and habitat environments. Lotters et al. (2004), 

Thomas et al. (2004), Pounds et al. (2006), and Bosch et al. (2007) make strong cases for the interaction 

of climate change and chytrid fungus as responsible for amphibian declines. 

Pounds et al. (2006) used a detailed analysis, including satellite imagery, to support the “chytrid thermal 

optimum” hypothesis driven by climate change. They hypothesized that cloudier cooler days and warmer 

nights in the montane Neotropics would produce the ideal atmospheric envelop for optimal chytrid fungus 

growth, and address the paradox that chytrid fungus is a cold tolerant pathogen, but amphibian mortality 

was in warm years. Chytrid fungus is more pathogenic to amphibians at lower temperatures (Berger et al. 

2004, Retallick et al 2004). Analyzing the timing of amphibian losses in relation to changes in air and sea 

61

temperatures in the montane Neotropics Pounds at al concluded with very strong confidence (>99%) that 

large-scale warming is the key factor in these declines and extinctions. Greenhouse warming intensified 

the hydrological cycle and was accompanied with aerosol pollution. These agents influenced cloud 

formation patterns, and thermal, moisture, and light regimes; resulting in warmer nights and increased 

daytime cloud cover. The local climatic change shifted mid-elevation sites into the thermally optimum 

environment for chytrid fungus. This is the elevation band (1000-2400 meters) where most of the 

Atelopus extinctions have occurred. 

Despite all the apparent associations among climate change, chytrid fungus infections, and large-scale 

amphibian population declines and direct mortality, recent research has found these relationships complex 

and often contradictory. The chytrid – climate change hypothesis has been rigorously challenged (Alford 

et al. 2007, Lips et al. 2008, Rohr et al. 2008). 

Climate change is almost certainly the direct cause of the severe decline of Yellowstone National Park’s 

amphibian fauna (McMenamin et al. 2008). Northern Yellowstone’s lower Lamar Valley was 

characterized by its rich amphibian fauna, as a direct resulted of its glacially sculptured landscape of 

moraines, kame terraces, and kettle ponds (Koch and Peterson 1995). These fishless ponds were 

recharged by groundwater and spring runoff. However, the ponds have been drying up. The Palmer 

Hydrology Drought Index for Yellowstone between 1895 and 2005 clearly reveals the climate changes 

(McMenamin et al. 2008, Figure 2). Yellowstone had a relatively wet climate between 1895 to the early 

1950s. Drought years have increased since the mid 1970s, and drought years have been severe and 

consistent after 1995. 

McMenamin et al. compared Yellowstone amphibian pond surveys that were conducted in 1992-1993 to 

ones conducted in 2006-2008. In 15 years, more than half of the ponds disappeared, and permanently dry 

ponds increased by a factor of four. The ponds with water held fewer species, and the proportion of 

ponds supporting amphibians had steeply declined. In the 1950s, all four of Yellowstone’s native 

amphibian species were considered common (Koch and Peterson 1995). Three species were common in 

the 1992-1993 surveys: Blotched Tiger Salamander (Ambystoma mavortium melanostictum), Columbia 

Spotted Frog (Rana luteiventris), and Boreal Chorus Frog (Pseudacris maculata). The new surveys 

documented that the Tiger Salamander declined by 50%, the Columbia Spotted Frog by 68%, and the 

Boreal Chorus Frog by 75%). 

The Boreal Toad was once very abundant in the Greater Yellowstone Ecosystem (see section Boreal 

Toad). In the 1992-1993 surveys, the Boreal Toad (Anaxyrus boreas boreas) was present, but 

uncommon. Three populations of the Boreal Toad were found in 1993, and these were also found in the 

2006-2008 surveys, based on eggs and tadpoles; but there were no ponds that supported all four species of 

amphibians. Interestingly and significant, was that in the entire 2006-2008 survey period only a single 

adult Boreal Toad was seen by surveyors! 

The role of chytrid fungus in the Yellowstone declines is unknown, but the fungus is known to attack all 

four species. McMenamin et al. observed severe mortality of Tiger Salamander larvae in three different 

ponds. However, the role of pathogens, lethal high temperature, or increased mineral or salt 

concentrations could not be established. This species has been susceptible to mortality from bacteria 

infections (Worthylake and Hovingh 1989). 

Amphibian populations have been surveyed at the Savannah River Site in South Carolina continuously for 

35 years. This site is a large relatively natural restricted area used for nuclear research and ecological 

investigations. Daszak et al. (2005) examined archived museum specimens of 15 anuran species for 

chytrid fungus infections. The fungus was detected (1978 to 1981 specimens) in three individuals of two 

species out of 137 individuals, but lesions were not present to indicate fatal pathology. Population 

62

trajectories over 26 years for six anurans and three salamanders indicated that two species of anurans and 

two salamanders showed statistically significant declines, one salamander showed a significant increase, 

while the other four anuran populations remained stable. Daszak et al. based on the specific requirements 

of life history requirements of these species, concluded that the population declines were the result of 

insufficient precipitation and shortened hydroperiod at breeding sites, related to a regional drying trend in 

the 1990s. This suggests climate change, but cannot rule out random long-term regional weather 

fluctuations. The research does point out that at least in some amphibian communities chytrid fungus 

infection does not necessarily result in population declines. 

Chytrid Fungus 

A species of chytrid fungus (Batrachochytrium dendrobatidis) (BD) has been conclusively implicated in 

amphibian declines throughout the world (Young et al. 2001, Daszak et al. 2003, Briggs et al. 2005, La 

Marca et al. 2005, Lips et al. 2006, Rachowicz et al. 2006, Skerratt et al. 2007, Collins and Crump 2009 

[pages 159-174], Rosenblum et al. 2010). Nevertheless, the importance of BD to explain global 

amphibian population declines has been challenged as being inconclusive (McCallum (2005). A 

chytridiomycete fungus was first associated with anuran die-offs in Australia and Central America 

(Berger et al. 1998). This fungus was described as a new genus and species of chytrid fungus (Longcore 

et al. 1999). The prevalence and infection potential of BD may be seasonally dependent (Kriger and Hero 

2007). Attempts have been made to predict the distribution of BD based on modeling environmental 

variables in a GIS environment (Ron 2005). Although the complete pathogenicity and virulence of BD 

has yet to be settled, for a brief and easy to understand life history and currently understood pathogenesis 

of BD see Rosenblum et al. (2010). 

Chytrid fungi represent a primitive group of fungi, Chytridiomycota, with five orders, approximately 

1000 species, and BD is unique and phylogenetically distinct (James et al. 2006). Chytrids are closely 

related to protozoans, because of their ancestry. Chytrid fungi are globally distributed from the tropics to 

arctic regions in diverse habitats. Most species are probably terrestrial and saprophytes, breaking down 

and feeding on keratin, chitin, and cellulose. Some soil chytrids are plant pathogens. There are 

freshwater and marine species that are parasites of algae and plankton. BD is the only known chytrid to 

parasitize vertebrates (Longcore et al. 1999). In most habitats, a few species may by widespread and 

abundant, especially in freshwater or disturbed soils, but most species are infrequent and rare (James et al. 

2006). Chytrid fungi are recognized from as far back as the Devonian (Hass et al. 1994), which ended 

354 million years ago. 

Chytrid infection (chytridiomycosis) initiates when fungal zoospores first encounter amphibian skin and 

quickly give rise to sporangia, which produce new zoospores, and the disease progresses as zoospores 

keep reinfection the host, resulting in the sloughing of epidermal tissue and reddening of ventral skin 

(Berger et al. 2005a). BD causes complex cellular changes resulting in reorganization, dissolution, and 

premature keratinization of infected cells (Berger et al. 2005a). The resulting histology suggests that 

toxicity is the cause of death, but inhibition of skin function and overgrowth of bacteria may contribute to 

pathogenesis. Amphibian skin is extremely critical to the physiology, respiration, osmotic balance, and 

moisture homeostasis of amphibians (Feder and Burggren 1992). BD has specific adaptations that 

suggest it has evolved for a long time to live within the cellular tissue of stratified epidermis (Berger et al. 

2005a). The original evolutionary selective forces for chytrid fungi were their saprophytic ecological role 

to decompose cellulose, hemicellulose, chitin, and keratin. This was therefore, a preadaptation for BD 

amphibian pathology attacking highly keratinized skin tissue, and other species to infect plant cell walls. 

Besides the metabolic toxicity and physiological degradation caused by BD, associated behavior includes: 

lethargy, reduction of reflex actions, abnormal posture, and a failure to seek shelter or flight. All of these 

result in high mortality to infected anurans. 

63

It is widely recognized that trying to detail and pinpoint the causes for the dramatic widespread amphibian 

declines are complex, confounding with multiple potential causes, and often contradictory (Kiesecker et 

al. 2001, Carey and Alexander 2003, Lannoo 2005, Blaustein and Bancroft 2007, Collins and Crump 

2009, pages 123-158). The complex and often inconclusive associations of BD with climate change, 

pesticides, and UV radiation was discussed above. 

There are a number of theoretically potential hypotheses to explain BD epidemics. First of all, there is the 

“novel pathogen” hypothesis, where the pathogen is transferred and spread geographically over time and 

space from a source. A competing hypothesis is that the pathogen was always widespread and endemic, 

but not virulent. It has recently become deadly for potentially three reasons. BD evolved into a new 

virulent infectious strain. BD switched hosts. BD is only virulent or increases its infection if its host is 

already stressed or subjected to one or more other insults. In other words, BD may not have previously 

involved with amphibians; BD may have been a minor amphibian parasite easily controlled by its host; 

BD may have infected one or more non-amphibian hosts (seriously or minimally); BD may have only 

attacked amphibians as they were dying from other causes or were already carcasses. Another possibility, 

of course, is that frogs evolved a strong susceptibility to BD. However, it is extremely unlikely that so 

many species from so many diverse families of anurans from all around the world all suddenly “evolved” 

into susceptibility to also a new species of chytrid fungus. 

Anurans and chytrid fungi were certainly around together for a very long time. The first known true frog 

(Vieraella herbstii) was from the Lower Jurassic (205 million years ago) of Argentina (Lecointre and Le 

Guyader 2006), but anuran ancestors go back to at least the early Permian, close to 300 million years ago 

(Anderson et al. 2008). Because chytrids have been around for over 354 million years there was certainly 

time to get acquainted. Therefore, if BD was a novel spreading pathogen it must have already evolved 

into a virulent species in at least a single locality. 

Ouellet et al. (2005) examined epidermal chytrid fungus infection for 3371 postmetamorphic and adult 

amphibians collected from 1895 to 2001 from Canada, United States, and 23 other countries. The data are 

summarized in Table 1. Note that most of the data is from Quebec (N=1998), while the remaining data 

were from: rest of Canada (N=623), United States (N=310), and 23 other countries (N=440). Most of the 

Quebec data were in the St. Lawrence River Valley, including Montreal and Mont Saint-Hilaire Biosphere 

Reserve. Cutaneous chytrid fungus infections were found in 383 (13.1%) specimens of 12 common 

amphibian species from five Canadian provinces and seven U.S. states. Chytrid infection was not found 

on any of their 440 specimens from 23 other countries. However, they did not investigate specimens from 

severe BD infected areas in Australia and Central America (e.g., Costa Rica), although, they did have 

some specimens from New Zealand and Panama. 

Time 

Period 

Quebec Rest of Canada 

Number BD Percent Number BD Percent 

Examined Infected Infected Examined Infected Infected 

1895-1959 38 0 0 136 0 0 

1960-1969 217 29 13.4 316 16 5.06 

1970-1979 30 8 26.7 126 2 1.59 

1980-1989 15 6 40.0 45 0 0 

1990-2001 1698 302 17.8 0 ------ ------ 

1960-2001 1960 345 17.6 487 18 3.70 

64

Time 

Period 

United States 

Number BD Percent 

Examined Infected Infected 

1895-1959 29 0 0 

1960-1969 122 1 0.820 

1970-1979 89 10 11.2 

1980-1989 63 8 12.7 

1990-2001 7 1 14.3 

1960-2001 281 20 7.12 

Table 1. Chytrid fungus (Batrachochytrium dendrobatidis) infection for 3371 postmetamorphic and 

adult amphibians collected from 1895 to 2001 from Canada, United States, and 23 other countries. 

The data is summarized from Ouellet et al. (2005, Table 3). 

There were a number of important conclusions from the research by Ouellet et al. (2005). The earliest 

chytrid infections found were in two Green Frogs (Lithobates clamitans) collected in July 1961 in 

Quebec. Importantly, the 1990-2001 data included 1698 specimens from Quebec, none from the rest of 

Canada, and only seven from the United States. All of the data for the 1698 specimens from Quebec were 

obtained from live captures in the field. Quebec infection rates did not differ statistically between the 

1960-1969 through 1990-2001 sampling periods (chi square: P=0.10), and the infection rate over this time 

frame was 17.6 percent. Over the same time frame the infection rate was 7.12 percent in the United States 

samples, and very low in the rest of Canada. However, sample sizes were low, and no samples were 

examined in the critical 1990-2001 time frame in the rest of Canada. The United States samples from 

1960-1969 had a very low infection rate, and if this time frame were excluded from analysis, the infection 

rate rose to 11.9 percent. Despite the fact that 17.8 percent of the live Quebec amphibians captured in the 

field between 1990 and 2001 tested positive for chytrid fungus, the individuals appeared healthy. Ouellet 

et al stress that even this unexpected high level of infection was very conservative, because the fungus 

assay was conducted from toe clips tissue. Chytrid fungus infection is most intense in the ventral pelvic 

region, ventral hind limbs, and hind feet (Berger et al. 1998). Chytrid infection was most prevalent in the 

spring and fall for the live specimens data. This corresponds to the reports of Longcore et al. (1999) and 

Carey (2000) the BD grows better at lower temperatures. Additionally, the immune system of amphibians 

functions more effectively at higher temperatures (Cooper et al. 1992, Carey 2000). 

The third time was not a charm for amphibians: first Homo sapiens, then HIV/AIDS, and now 

Batrachochytrium dendrobatidis. The oldest known identification of chytridiomycosis was in a 1938 

African Clawed Frog, Xenopus laevis (Weldon et al. 2004). The individual was found in a series of 697 

archived Xenopus frogs (3 species, 84% X. laevis), collected between 1879 to 1999 in southern Africa. 

All three species were infected with a prevalence of 2.7%, and all regions of southern Afrtica were 

infected by 1973. Therefore, this evidence is frequently cited for the out of Africa origin of BD. 

However, this question remains unsettled, because recent genetic evidence shows low diversity of BD in 

Xenopus and high allelic diversity in North American Bullfrogs (James 2009, Rosenblum 2010). See 

Discussion section for more detailed information. 

The next oldest date of known BD infection was 23 years later in a Green Frog from Quebec (Ouellet et 

al. 2005), and was discussed above. X. laevis is a completely aquatic species that does not exhibit clinical 

symptoms in wild populations, and has not experienced sudden die-offs. Importantly, only subclinal 

65

chytrid infections have been observed in captive colonies of this species (Weldon et al. 2004). Typically, 

anurans in captivity that become infected with BD suffer rapid and complete mortality, because the 

fungus spreads rapidly by contact (Young et al. 2007, Une et al. 2008). 

Exceedingly large numbers of X. laevis were caught in the wild in southern Africa and spread around the 

world after 1934, the year of the discovery that this species was a rapid and effective test for human 

pregnancy (Weldon et al. 2004). Additionally, many specimens were used as experimental laboratory 

subjects and widely distributed in the pet trade. African Clawed Frogs were very abundant and available 

in both research laboratories and pet stores in the eastern United States during the 1970s (A.J. Krzysik, 

personal observation). X. laevis has been recorded in the wild in ten states, but has only been established 

and breeding in seven counties of southwestern California and golf course ponds in the Tucson area of 

Arizona (Crayon 2005). It was first recorded as a feral species in California in 1968. 

Boreal Toads 

Results 

The Western Toad (Anaxyrus sp [formerly Bufo]) group consists of five currently recognized taxa, three 

of them isolated endemic relicts that are extremely local (Goebel 2005). The Amargosa Toad (Anaxyrus 

nelsoni) is found in a ten-mile stretch of the Amargosa River and associated springs in Oasis Valley in 

southwestern Nevada near Beatty. The Black Toad (Anaxyrus exsul) is found in Deep Springs Valley 

between the Inyo and White Mountains in eastern California near the Nevada border. The Yosemite Toad 

(Anaxyrus canorus) is found in the high Sierras, mainly between elevations of 9000 to 12000 feet in the 

vicinity of Yosemite National Park. The California Toad (Anaxyrus boreas halophilus) is found 

throughout most of California with the exception of deserts and the highest mountain elevations, into 

extreme western Nevada, and south into Baja California Mexico. The Boreal Toad (Anaxyrus boreas 

boreas) has a very extensive distribution, ranging from all of Southeast Alaska, all of British Columbia, 

and western Alberta in the north; south to northern California, most of Nevada north of the Mojave 

Desert, and the mountains of Utah; and east to western Montana, western and southern Wyoming, the 

Rocky Mountains of Colorado, and extending into the northern extreme of New Mexico. The two 

subspecies intergrade in northern California. The Boreal Toad is commonly referred to as the Western 

Toad in much of the literature. Nevertheless, the correct and taxonomically accepted nomenclature is that 

the Western Toad refers to both subspecies of Anaxyrus boreas. 

The three taxa with very local distributions are always in danger of extinction from epidemics, climate 

change, unusual weather, or some local habitat/environment insult. The habitats of all three are currently 

protected, conservation plans are in place, populations are monitored, and only the Yosemite Toad has 

shown a decline (Davidson and Fellers 2005, Fellers 2005, Goebel et al. 2005). Boreal and California 

toads have shown severe declines in most of their range (Muths and Nanjappa 2005). 

Goebel (2005) actually recognized nine phylogenetic clades of this complex based on mitochondrial DNA 

parsimony analysis, and concluded that additional analyses are needed for any final Linnaean 

classification. She verified the three recognized species, and produced six clades of Anaxyrus boreas. 

The phylogenic higher order clade covering Southeast Alaska is the Northwest clade (at Node 8). Node 8 

gave rise to four terminal nodes: Anaxyrus canorus, West Coast, Midwest, and Far North. These three 

clades were not further defined. Southeast Alaska Anaxyrus boreas is a component of four terminal 

phylogenetic clades, presumably the Far North clade, and it is interesting that it is related to the Yosemite 

Toad. 

All species of native true frogs (Ranidae) have dramatically declined in the western United States (Hayes 

and Jennings 1986). Although much of the decline can be attributed to habitat loss or degradation, the 

66

dramatic decline of nine ranid California frogs in pristine habitats is puzzling (Jennings 1995). There has 

been a general decline of five species of anurans, including the Boreal Toad, from northern Colorado to 

southern Wyoming (Corn and Fogleman 1984). The decline of Yosemite Toads was blamed on drought, 

disease, and predation, with the conclusion that multiple factors could be particularly devastating 

(Kagarise Sherman and Morton 1993). Kagarise Sherman and Morton (1993) provide an interesting 

literature review and their own observations of avian predation on toads. Three species of corvids were 

involved in predation on toads in the Boreal Toad species group. See Predation Section for details. 

Boreal Toads in the Central and Southern Rocky Mountains 

The Boreal Toad, a once very widely distributed and very abundant species, underwent extensive declines 

in both distribution and abundance in the central and southern Rocky Mountains from the late 1970s to 

the present (Carey 1993, Stuart and Painter 1994, Corn et al. 1997, Livo and Loeffler 2003, McGee and 

Keinath 2004, Carey et al. 2005, Collins and Crump 2009, pages 135-142). This region covers the states 

of Colorado, Wyoming, Utah, and a small area of extreme northern New Mexico. The Boreal Toad may 

be extinct in New Mexico (Degenhardt et al. 1996). Boreal Toads were historically common up to the 

1960s in the Wasatch and Uinta Mountains in northern Utah, but appear absent or in decline throughout 

the state (Ross et al. 1995, Stebbins and Cohen 1995). Recent surveys found northern populations scarce, 

but three scattered small new populations were discovered in southern Utah (Ross et al. 1995). There 

were only five previously know populations in the southern portion of the state based on museum records. 

Ross et al. concluded that the state has not been adequately surveyed for Boreal Toads, and that the 

disjunct montane habitats in the state make it difficult for recolonization of local population when they go 

extinct. 

Corn et al. (1989) reported that Boreal Toads were absent at 49 out of 59 (83%) of their historical sites in 

Colorado and Wyoming. Populations appeared stable until there were major die-offs in 1996 and in 1999 

(Carey 2000, Carey et al. 2005). Some early population mortality was attributed to bacterial infections 

(Carey 1993). Corn (1998) concluded that UV radiation was not responsible for Boreal Toad declines in 

the pristine landscape of Rocky Mountain National Park in northern Colorado, but there were 

contradictory results in other studies of UV radiation. Chytrid fungus was identified with declining 

Boreal Toad populations, as well as other anurans, in Colorado and Wyoming (Daszak et al. 1999, Muths 

et al. 2003, Keinath and McGee 2005). Scherer et al. (2005) concluded that chytrid fungus and not 

weather conditions were responsible for the significant decline of two major populations of Boreal Toads 

in Rocky Mountain National Park. 

Many factors have been blamed for the decline of populations in the Boreal Toad group, but the reports 

have often been inconclusive and even contradictory. The typical agents identified as potentially 

responsible for the decline of Boreal Toads, either alone or in concert are: chytrid fungus, pathogens such 

as other fungus or bacteria, habitat destruction and degradation, increased predation from both introduced 

and native predators, pesticides, acidic deposition, acid and minerals from mine water seepage, increased 

UV radiation, timber harvest, livestock grazing of wetlands, fire and fire management, and competition 

from introduced fathead minnows (McGee and Keinath 2004, Keinath and McGee 2005, Muths and 

Nanjappa 2005, Maxell et al. 2009). 

Collins and Crump (2009, page 142) concluded that as of January 2008 there were only 33 known 

populations of Boreal Toads in Colorado. Most of the northern populations are infected with chytrid 

fungus, but it appears that most of the southern populations are free of the fungus. The status of the 

Boreal Toad in the central and southern Rocky Mountains is currently under rigorous investigation. 

Boreal Toads have dramatically declined in the Greater Yellowstone Ecosystem (Koch and Peterson 

1995, Patla and Peterson 1999, McMenamin et al. 2008). Carpenter (1953, 1954) referred to the Boreal 

67

Toad as the most widespread amphibian in the Jackson Hole region, and reported that it was found in 

every locality in a great variety of habitats. Turner (1955) remarked about the large numbers of crushed 

toads he observed on the roads around Yellowstone Lake and Fishing Bridge over the Yellowstone River. 

Koch and Peterson (1995) reported that they observed only two Boreal Toads in this same area over the 

last six years (pre early 1990s). They also reported that only three of 48 sites examined in northern 

Yellowstone National Park had Boreal Toads in 1992-1993, but at times the region supported successful 

reproduction in some areas. They concluded that this species had declined over the last 40 years (1950s 

to early 1990s) in the Greater Yellowstone Ecosystem. The same three populations of Boreal Toads 

found in 1993 were also found in 2006-2008 amphibian surveys (McMenamin et al. 2008). However, the 

documentation of Boreal Toads was based on the presence of eggs and tadpoles, because during the entire 

2006-2008 survey period, only a single adult Boreal Toad was seen by surveyors! The 1992-1993 and 

2006-2008 Yellowstone amphibian survey comparison was discussed above (see Climate Change, 

McMenamin et al. 2008). 

Boreal Toads in the Northern Rocky Mountains 

The Montana Natural Heritage Program has put in a great deal of effort conducting extensive amphibian 

and reptile surveys on at least six National Forests, Glacier National Park, BLM lands, Flathead Indian 

Reservation, and National Wildlife Refuges. At least 15 reports have been submitted from 1994 to 2000, 

totaling over a 1000 pages (Montana Herps 2010). The data from these surveys and the available 

literature were synthesized to develop a comprehensive conservation and management plan for the state’s 

herpetofauna, including the Boreal Toad (Maxell et al. 2009). The following data on the Boreal Toad is 

from these series of reports. 

Biologists were of the opinion that Boreal Toad population in the northern Rocky Mountains were more 

stable, and did not undergo the dramatic declines of the central and southern Rockies. However, these 

surveys revealed that although Boreal Toads were still widespread in distribution, that were absent from 

many of their historical localities, and they occupied typically less than ten percent of suitable habitat, but 

often even less than five percent. The Montana 2000 systematic inventory of 40 randomly chosen 6 th 

level Hydrologic Unit watersheds found the toads widespread but very rare. They were only found in 11 

(27%) of the watersheds, and of the 33 watersheds with suitable breeding habitat the toads were breeding 

(eggs, larvae, or metamorphs observed) in only seven (21%). A total of 347 standing ponds and pools 

were surveyed in these watersheds, and adults were only found at 13 (3.7%), while toads were breeding in 

only 9 (2.6%). Importantly, at sites where toads were found, only few adults, larvae, or eggs were 

observed. Similarly, approximately 400 standing bodies of water were surveyed at Glacier National Park 

during the summers of 1999-2000, and Boreal Toads were only found and breeding at approximately five 

percent of the sites. Again, the surveys at the Flathead Indian Reservation in 1999-2000 were similar, 

where toad breeding occurred at four of nine historical sites, and years between breeding were often 

skipped. 

The Boreal Toad in Montana has received the following status (MNHP 2009). 

Global Designation G4 

Uncommon but not rare (although it may be rare in parts of its range), and usually widespread; 

apparently not vulnerable in most of its range, but possibly cause for long-term concern. 

State Designation S2 

At risk because of very limited and/or declining numbers, range, and/or habitat, 

making it vulnerable to global extinction or extirpation in the state. 

Montana CFWCS Tier I 

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Montana Fish, Wildlife, and Parks; Comprehensive Fish and Wildlife Conservation Strategy identifies 

fish and wildlife species that are in greatest need of conservation by ranking them into one of four Tiers. 

Tier I represents the highest level of species protection. 

“Tier I: Greatest conservation need. Montana Fish, Wildlife & Parks has a clear obligation to use its 

resources to implement conservation actions that provide direct benefit to these species, communities, and 

focus areas.” 

Boreal Toads in the Pacific Northwest 

Despite the severe well-documented declines of Boreal Toads in the central and southern Rocky 

Mountains of Colorado and Wyoming, and also to probably a smaller degree in the northern Rockies of 

Montana, there is no evidence that this species has experienced serious declines in the mountains of the 

Pacific Northwest (Muths and Nanjappa 2005). Boreal Toads are rare in the lowlands of the Pacific 

Northwest (Richter and Azous 1995, Adams et al. 1998, 1999). Pearl et al. (2007) examined 210 anurans 

of seven species from 37 sites in Oregon and Washington. Four of the seven species tested positive for 

chytrid fungus, with infection rates ranging from 9-57 percent. The introduced Bullfrog tested positive 

for 15 of 48 (31.2%) individuals. The fungal infections were from all parts of Oregon, and none were 

found for Olympic National Park, Washington. All stages of anurans were infected (adults, 

metamorphs/juveniles, and tadpoles). Infection rates were six times greater in winter and spring than in 

summer. None of the 13 Boreal Toads examined was infected. 

Four species of anurans and a salamander are currently abundant within the blast zone of the 1980 Mount 

St. Helens eruption, and they colonized all available lake habitats within five years of the eruption, despite 

the complete lack of dispersal corridors (Crisafulli and Hawkins 1998). However, the terrestrial family of 

Plethodontidae salamanders was apparently eliminated. 

Blaustein et al. (1994b) found that the widespread fungus Saprolegnia ferax had contributed to Boreal 

Toad egg mortality of 50 to 95 percent in three populations in the Cascade Mountains of Oregon since 

1989. However, from 1980 to 1989 natural mortality of eggs had been less than five percent. 

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Chytrid Fungus Analysis for Soule River Watershed, Southeast Alaska

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