Undergraduate Honors Theses

Thesis Defended

Spring 2015

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Ecology and Evolutionary Biology

First Advisor

Chris Ray

Second Advisor

Barbara Demmig-Adams

Third Advisor

Carol Wessman

Fourth Advisor

Kendi Davies

Fifth Advisor

Jason Neff

Abstract

Small mammals that make use of sub-surface microclimates may be able to adapt quickly to a warming climate by altering the level and timing of certain surface activities. For example, energy-intensive territorial defense or foraging activities might be shifted to cooler times of day. This hypothesis was explored using data on the American pika (Ochotona princeps), a small, diurnal lagomorph closely related to rabbits that uses rocky microhabitats for shedding heat between bouts of surface activity. Over three consecutive summers (mid-June to mid-August, 2012-2014), 94 observations (45 minutes each) were conducted involving N = 61 unique pikas, using a standardized protocol to record behaviors during continuous focal-animal sampling. During observations, data loggers were used to record shade temperatures in surface and sub-surface microhabitats available to the focal pika. Most observations were conducted at the Niwot Ridge Long Term Ecological Research (NWT LTER) site in Boulder County, Colorado (USA), with the goal of comparing historical data from this site with contemporary and future data. Here, I report a contemporary, temperature-indexed activity budget for pikas in this area of the southern Rocky Mountains. Surface temperatures averaged 5-10°C higher than sub-surface temperatures during diurnal observations, and pikas spent two-thirds of their time below the surface. Modeling surface activity as a function of microclimate and microhabitat variables, sub-surface temperature was found to be able to serve as the basis of a significant predictor model. The average surface-sub-surface temperature differential was also found to a significant non-linear model, surface temperature (values ≤ 15°C). This suggests that a strong temperature gradient is more important when the surface temperature is greater than 15°C. This study provides a current baseline for studying any future shifts in pika behavior, by providing data on behavior and temperature variation within currently available microhabitats, and by characterizing how pikas respond to temperature at this point in time.

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