2018 ESA Annual Meeting (August 5 -- 10)

COS 109-4 - Changing snowmelt and plant phenology conditions are altering elk migration timing in the Greater Yellowstone Ecosystem

Thursday, August 9, 2018: 2:30 PM
339, New Orleans Ernest N. Morial Convention Center
Gregory J.M. Rickbeil1, Jerod A. Merkle2, Matthew J. Kauffman3, Paul Atwood4, Jon Beckman5, Eric Cole6, Alyson Courtemanch7, Sarah Dewey8, David Gustine8, Doug McWhirter9, Kelly Proffitt10, P.J. White11 and Arthur D. Middleton12, (1)Environmental Science, Policy, and Management, University of California - Berkeley, Berkeley, CA, (2)Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology, University of Wyoming, Laramie, WY, (3)United States Geological Survey, (4)Idaho Department of Fish and Game, (5)Wildlife Conservation Society, (6)National Elk Refuge, U.S. Fish and Wildlife Service, Jackson, WY, (7)Wyoming Game and Fish Department, (8)National Park Service, (9)Wyoming Game and Fish Department, Jackson, WY, (10)Montana Fish Wildlife and Parks, Bozeman, MT, (11)Yellowstone Center for Resources, National Park Service, Yellowstone National Park, WY, (12)Department of Environmental Science, Policy, and Management, University of California - Berkeley, Berkeley, CA
Background/Question/Methods

Long-distance mammal migrations face many new pressures globally. In North America, land management practices, development, and changing environmental conditions have contributed to the decline of migratory behavior in multiple mammal species, including elk, the most numerous ungulate in the Greater Yellowstone Ecosystem (GYE). Here, we examine (1) how migration timing changed from 2001 to 2015 in nine herds of partially migratory elk across the GYE, (2) what the environmental determinants of migration timing are in spring and fall, and (3) how these environmental determinants have changed since 2001 for each herd. Due to regional observations of drought and warming, we hypothesize that elk will migrate earlier in spring and later in fall. We expect vegetation green-up and snowmelt to be important environmental factors governing spring migration and snow accumulation and plant senescence to be linked to fall migration. Lastly, we expect snow melt and vegetation green-up to advance throughout the study period and snow accumulation and plant senescence to occur later. We test this using the most comprehensive dataset assembled on elk migration in the GYE, representing 285 spring migrations and 215 fall migrations linked to estimates of snow cover and plant phenology while controlling for hunting and supplemental feeding.

Results/Conclusions

In spring, elk departed winter ranges earlier but spent more time in migration corridors, resulting in no significant change in arrival date on summer range. In fall, elk departed summer range later and spent more time in migration corridors resulting in later arrival dates on winter range. Snow melt and green-up were the environmental factors most strongly linked to spring migration initiation, while snow melt and the date of maximum instantaneous rate of green-up were associated with arrival date on summer range. Plant senescence and snow accumulation were associated with fall migration initiation while snow accumulation was linked to arrival date on winter range. On average, from 2001 to 2017 the timing of snow melt and spring green-up advanced with more rapid advances occurring at higher elevations; plant senescence occurred later in the year with higher elevations again displaying more rapid changes while snow accumulation also occurred later. These results demonstrate that across the GYE (1) migration timing of elk is changing at a significant rate, (2) environmental conditions can explain much of the variance in migration timing, and (3) these environmental factors are changing in a way which is consistent with changing elk migration timing and changing climatic conditions.