LB 4-20 - Behavioral Responses to Climate Change in Chipmunks of the Sierra Nevada

Background/Question/Methods:

Climate change is having profound effects on the distribution of species across the globe, particularly on species living at high elevation. There is deep interest in exploring how behavioral flexibility allow organisms to cope with anthropogenic environmental change. In apparent association with changing climate in the last century, the high elevation specialist alpine chipmunk (Tamias alpinus) has experienced a significant upward contraction of its elevational range; in contrast, the partially sympatric generalist lodgepole chipmunk (Tamias speciosus) has undergone no detectable change in elevational distribution. Using this comparative system, we investigated how individual behavioral flexibility, particularly exploration and boldness, underlie the differential climate-induced range shifts in these species. Exploratory behavior is defined as an individual’s propensity to sample a novel environment, while boldness describes how quickly animals engage with novel stimuli, and both have been shown in a variety of taxa, including chipmunks, to facilitate survival in novel and changing environments. During the summers of 2018-2021, we live-trapped individuals of each species from multiple localities in California’s Eastern Sierra Nevada range, and permanently marked individuals with RFID PIT tags.

Results/Conclusions:

Upon recapture, we placed tagged individuals in an arena to undergo an open field test, a standard assay for exploratory behavior. Individuals were filmed for a 10 minute period, and behavioral data, such as boldness, activity, and exploration, were extracted from the resulting footage. We found that T. speciosus individuals were more bold and more active on average than T. alpinus individuals, but there was little difference in exploratory behavior. The observed differences in boldness align with previous findings in this system, and our understanding of how these behaviors facilitate population responses to environmental change. Namely, bolder individuals tend to be more successful at capitalizing on novel resources in a changing environment. However, our findings regarding exploratory behavior are far less clear cut, reflecting the myriad competing pressures driving variation in this complex behavior. As humans continue to modify the environment, understanding individual behavioral variation can provide mechanisms for the heterogenous and often unpredictable responses of populations to their changing environments.