alpine meadows, sierra nevada bighorn sheep, and wilderness
alpine meadows, sierra nevada bighorn sheep, and wilderness
alpine meadows, sierra nevada bighorn sheep, and wilderness
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ALPINE MEADOWS AND SIERRA NEVADA<br />
BIGHORN SHEEP: WILL CLIMATE CHANGE<br />
IMPACT RECOVERY?<br />
Tom Stephenson, Lacey Greene, Mike Dodd,<br />
Lora Konde, <strong>and</strong> John Wehausen
Original Distribution of Sierra Nevada Bighorn Sheep
Current Distribution of Sierra Nevada Bighorn Sheep<br />
A. Lawrence
Kern<br />
Central<br />
Southern<br />
Northern<br />
160<br />
140<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
Current Estimate Goal<br />
Number of adult ew
Kern<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
0<br />
Current Estimate Goal<br />
Central<br />
Southern<br />
Northern<br />
Number of herd un
160<br />
0<br />
1975 1980 1985 1990 1995 2000 2005<br />
EWES<br />
140<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
Baxter, Bubbs,<br />
& Sawmill<br />
Total<br />
Williamson<br />
Langley<br />
Wheeler<br />
listing<br />
Mono Basin
Threats to Recovery<br />
• Small Population Size<br />
– Demographic concerns (e.g., Allee effect)<br />
– Genetic concerns (e.g., inbreeding<br />
depression)<br />
• Climate<br />
• Habitat/Forest Succession<br />
• Predation<br />
• Disease
Climate Change Predictions<br />
• Decline in <strong>alpine</strong><br />
meadow communities<br />
• Tree-line is expected<br />
to rise in elevation<br />
Lenihan et al. 2003. Ecol. Appl.
Shrinking Glaciers <strong>and</strong> Snowfields<br />
km2<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
1900 2004<br />
• Basigic documented a<br />
decline in the<br />
coverage of glaciers<br />
in the Sierra Nevada<br />
of almost 50% during<br />
the past century<br />
Basagic 2008. MS Thesis
Diet Quality among regions<br />
1.5<br />
Diet Quality (ln% fecal N)<br />
1<br />
0.5<br />
N AK N BC AB SN, CA WM, CA<br />
0<br />
J F M A M J J A S O N D<br />
Date
Availability of Meadows within Herd<br />
Units<br />
Mt. Warren<br />
Mt. Gibbs<br />
Wheeler<br />
Ridge<br />
Mt. Langley<br />
2%<br />
0.8%<br />
0.9%<br />
0.3%
Mt. Gibbs
Delineation of Meadows
Plot of Bighorn Locations
Use by larger populations<br />
• Greater selection<br />
during autumn<br />
• If <strong>meadows</strong> senesce<br />
early, nutrient<br />
availability will decline<br />
during pre-winter<br />
foraging that is<br />
important for fat<br />
deposition
Use by smaller populations<br />
• Gibbs exhibited<br />
strong selection<br />
– Meadows are at the<br />
core of their range<br />
• At Warren, apparent<br />
avoidance may be a<br />
function of low<br />
availability in the core<br />
of the range
Conclusions<br />
• Sierra <strong>bighorn</strong> populations are small<br />
relative to historic levels.<br />
• We hypothesize that as populations grow<br />
<strong>and</strong> exp<strong>and</strong>,<strong>meadows</strong> will become more<br />
essential for supporting larger populations.<br />
• Meadows on the periphery of some ranges<br />
may have yet to be discovered.<br />
• Importance of <strong>meadows</strong> may vary among<br />
granitic <strong>and</strong> metamorphic ranges.
12,000’<br />
5,000’
Prescribed Fire
Bighorn Use of Burns
Acknowledgements<br />
• CDFG<br />
• USFWS<br />
• BLM<br />
• Kathleen Knox<br />
• Dave German
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