FrogLog 103 PDF here - Amphibian Specialist Group

quantified in a network of 90 wetlands for
three years in an agricultural landscape
in Illinois. Our previous field experiments
demonstrated that desiccation risk varies
among matrix habitats, and that individuals
orient movements towards habitat with low
desiccation risk. We used cost-distance
modeling to generate a connectivity
metric that accounted for desiccation risk.
Occupancy and colonization probabilities
were related negatively to fish occupancy
and positively to connectivity. Matrix
structure had a strong influence on
colonization, and the connectivity metric
based on desiccation risk was a better
predictor of colonization than alternative
metrics. The positive effect of desiccationinformed
connectivity on colonization was
strongest in wetlands with fish, indicating
matrix composition can moderate the
effects of predation on amphibians. We
detected a rescue effect in which extinction
probability was related negatively to
connectivity, and this effect was strongest
in sites with fish. The matrix did not have
a strong effect on occupancy or extinction
probabilities, and we discuss why matrix
effects may vary for different aspects of
population turnover. Our results suggest
effects of fish predators on metapopulation
dynamics of amphibians depend on spatial
connectivity, and that immigration may
be essential for maintaining persistence of
amphibians in systems with fish. This study
also demonstrates that the mechanisms
underlying dispersal limitation for A.
tigrinum may include desiccation risk.
B. J. Cosentino, R. L. Schooley, C. A.
Phillips, Ecosphere 2, art95 (2011), http://
dx.doi.org/10.1890/ES11-00111.1
Assessing the use of non-lethal tail
clips for measuring stable isotopes
of plethodontid salamanders
Joseph R. Milanovich & John C. Maerz
Stable isotopes are increasingly used
in ecology to study the diets, trophic
position, and migratory patterns of wildlife
including herpetofauna. When using
stable isotopes, it is important to consider
which tissues can or should be sampled,
and how selecting tissues may affect the
inferences drawn from stable isotope data.
Amphibians offer fewer tissues than other
larger organisms that can be harvested
in sufficient quantity without killing the
animal; however, many salamanders
have tails that readily autotomize and
regenerate. We used three species of
plethodontid salamander (Plethodon
cinereus, P. metcalfi, and Desmognathus
quadramaculatus) to determine whether
distal tail tissue had carbon and nitrogen
stable isotope values comparable to
commonly used tissues (liver and whole
carcass [minus the liver and gonads])
that must be collected lethally. We found
that variation in carbon values (δ13C)
within and among tissues was negatively
correlated with C:N (an indication of high
lipid content). Nitrogen (δ15N) and Carbon
(δ13C) values (once adjusted for C:N) of tail
tissue were positively correlated with values
for carcass tissue, and tail δ15N values
were positively correlated and biased with
δ15N values for liver tissue. Adjusted δ13C
values for tail tissue were unbiased and
had weaker positive correlations with δ13C
values for liver tissue compared to whole
carcass. The weak correlation between
adjusted δ13C values of tail and liver tissues
may reflect differences in turnover rates
between the two tissues. Our data show
that, with calibration, non-lethal collection
of tail clips is a suitable substitute to lethal
tissue collection for measuring δ13C and
δ15N of plethodontid salamanders.
J. R. Milanovich, J.C. Maerz. Herpetol.
Conserv. Biol. 7, 67 (2012).
Field notes on findings of
threatened amphibian species
in the central mountain range of
western Panama
By Andreas Hertz, Sebastian Lotzkat, Arcadio
Carrizo, Marcos Ponce, Gunther Köhler & Bruno
Streit
Panama’s diverse fauna has suffered
from severe amphibian population
declines since the late 1990’s resulting in
the disappearance of many species in the
high mountains of the western part of the
country. During field work along a transect
in the Cordillera Central of western Panama
between 2008 and 2010, we searched for
lost species in remote areas and detected
several populations of amphibians
which are considered as Endangered
or Critically Endangered by the IUCN.
Most of these species have suffered from
serious population declines, probably due
to chytridiomycosis, but all are generally
considered to be threatened by habitat
loss. We detected 53% of the Endangered
and 56% of the Critically Endangered
amphibian species that have previously
View over the Cerro Colorado region, with the cone
shaped peak of Cerro Saguí in the background. Photo:
S. Lotzkat.
been reported from within the investigated
area. We report on findings of species that
have not been found in Panama for many
years, and provide locality data of newly
discovered populations. Among these
findings are populations of all three species
of Isthmohyla on the Lost Frogs list of the
IUCN SSC Amphibian Specialist Group,
which were detected in the Cerro Colorado
region in the Serranía de Tabasará.
Further studies will have to evaluate the
conservation status of these populations.
For many reasons, there is a need to create
a new protected area at Cerro Colorado,
which otherwise run the risk of getting lost
as an incredibly diverse and little explored
wildlife habitat. The most threatening
factors in this context are mining projects
and general deforestation.
A. Hertz et al., Amphib. Reptile Conserv.
6, 9(e46) (2012).
Connectivity of local amphibian
populations: modeling the
migratory capacity of radio-tracked
Natterjack toads
By Ulrich Sinsch, Neus Oromi, Claude Miaud,
Jonathan Denton & Delfi Sanuy
Many amphibian species are spatially
organized in interacting sets of local
populations (= metapopulations) rather
than in isolated populations or large
assemblages with unconstrained gene flux.
Knowledge on the spatial equivalent of an
amphibian population identified as a target
for conservation is crucial for successful
management measures. Estimates of the
individual variation of annual migratory
capacity within a local population allow
for (1) a scientifically founded delimitation
of core habitats around the breeding site
to improve long-term local persistence,
and provide (2) a quantitative measure
for connectivity among neighboring
populations, i.e. the magnitude of potential
genetic exchange.
We chose as a model organism the
European natterjack toad Epidalea (=Bufo)
calamita which is still listed as a “Least
Concern” species, but has suffered from
range contraction and loss of populations
at the northern range limits in the UK and
Sweden. The migratory behavior of 143
radio-tracked adults was monitored at eight
localities (latitudinal range: 41° - 54°N).
The multi-location approach permitted
us to assess the geographic variation
of migratory distance moved by adults
and to model their capacity for dispersal
assuming exclusively unidirectional
movements. Migratory range did not vary
between males and females, but was three
times greater in populations inhabiting
FrogLog 20 (4) | Issue number 103 (July 2012) | 41