Date of Award

Spring 5-21-2022

Degree Type

Honors Thesis

Major

Biology

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Scott Nunes

Second Advisor

Naupaka Zimmerman

Third Advisor

James Sikes

Abstract

Beginning in the 1900s, changes in climate have resulted in an increase in global temperatures. This warming has driven behavioral and demographic changes within a multitude of species worldwide. Historically, small mammal populations have responded to changes in temperature by adjusting their geographic ranges. As temperatures rise, high-elevation populations may no longer be able to adjust as they have before. In this study, we evaluated possible effects of climate change on a high-elevation population of Belding’s ground squirrels (Urocitellus beldingi) at Tioga Pass in Northern California. We used local climate data and long-term population data from 1994 to 2021 at Tioga Pass to identify trends for change. A significant increase in mean annual daily minimum and daily mean temperature was observed. We also observed a significant decrease in the yearly number of litters weaned. Annual means of daily minimum and daily mean temperature are reliable predictors of the number of litters weaned during a year. Declines in the number of litters weaned varied across areas within the study site suggest that possible effects of climate change on the U. beldingi population may have been affected by local features within the overall habitat. Body mass of juvenile U. beldingi near the time of weaning increased, suggesting that maternal female U. beldingi may be better able to channel energy to their offspring under low-density conditions. Declines in the U. beldingi population at Tioga Pass are consistent with models predicting losses of high-elevation populations of small mammals as the climate continues to warm.

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