Pika response to microhabitats on Niwot Ridge
Other: Honors thesis, University of Colorado Boulder, 2018.
Biodiversity is integral to healthy ecosystems, but is decreasing globally as climate changes. Indicator species like the American pika, Ochotona princeps, serve as a measure of ecosystem health and can suggest how other organisms might be impacted in the future. Pikas regulate their body temperature through behavioral changes, such as resting in cool sub-surface spaces between rocks. The range of pika occurrence has retracted from many lower elevation sites as temperatures increase; however, pikas persist in favorable microclimates and high elevations. This study compared the features of several pika territories in close proximity to understand why some remain occupied more than others. The recency or frequency of occupancy was compared to land cover, sub-surface temperatures, and pika thermoregulatory behavior. Grass cover was negatively correlated with recent pika occupation. Thermoregulation potential was defined as the sum of absolute differences in summertime temperatures near the surface and deep under the rocks, representing the range of temperatures accessible for a pika to shed heat. Thermoregulation potential exhibited a positive relationship with recent occupancy, while temperatures at shallow or deep sub-surface positions were no different across territories. Differences in the potential to support pika thermoregulatory behavior may thus be more important than absolute temperature. Climate-dependent pika behaviors did not vary significantly across territories, though trends were in the direction expected for behavioral thermoregulation. This study enhances our understanding of how animals’ territories in close proximity can vary in important ways, which can have implications in guiding human interventions as more taxa experience climate-related stress.