Print PageAlpine mammals are predicted to be among the species most threatened by climate change, but departures from this prediction may be expected for species specializing in microhabitats with less labile microclimates. For example, the American pika (Ochotona princeps) occurs primarily in rock-piles and is noted for its association with relatively cool and moist microclimates. This study addresses pika survival and signs of physiological stress in relation to microclimate as the basis for modeling the species’ response to climate change. Data are collected from two long-term study sites in a comparative study to test hypotheses that pikas experience higher physiological stress and lower survival in microhabitats with higher summer temperatures and lower winter temperatures. Pikas are marked and sampled at microsites differing in latitude, elevation and slope aspect in order to estimate survival rates and physiological parameters. The sub-surface microclimate experienced by each marked pika is characterized using a temperature data logger placed next to its central food cache. Data on survival and physiological parameters in relation to microclimate are analyzed annually from each of the two study sites, one in Montana (‘MT’) and one in Colorado (‘CO’), USA. Here, results are presented from the first year of this comparative study.
Results/Conclusions
In 2008, 51 pikas were tagged for survival analysis across the two study sites. Accounting for re-sight probability (>0.9), 95% confidence intervals for annual survival were 13-21% in CO and 55-73% in MT. Only the MT survival rate was within the range of published data for this species. In CO, the only surviving pikas were located on south-facing slopes, and survival on south-facing slopes was also higher among MT pikas. Microclimates were compared using bootstrapped 95% confidence bounds on average annual temperature profiles in CO vs. MT, and on north-facing vs. south-facing slopes within sites. CO microclimates exhibited significantly warmer temperatures in summer and significantly colder temperatures in winter than MT microclimates, and north-facing slopes in CO exhibited far more extremely cold temperatures (below -5°C) than south-facing slopes within that site. Levels of plasma glucose, which provides energy for the fight-or-flight response, were significantly higher in pikas from CO (mean±SE = 967.50±117.93 in CO, 449.59±102.91 in MT). Together, results support hypotheses that pikas experience higher physiological stress in microhabitats with higher summer temperatures and experience lower survival in microhabitats with lower winter temperatures.
