Sagehen Creek Field Station

15 Jun, 05 AM - 16 Jun, 05 AM

Background: Rapid climate change is causing species to shift their ranges (Parmesan and Yohe 2003). As the climate continues to warm, modeling studies project that climate change will emerge as a leading cause of global biodiversity loss (Thomas et al. 2004, Loarie et al. 2008). However, predicting the fate of individual species in the face of climate change is complex because it requires identifying the precise mechanism that control distribution and abundance for each species (Hijmans and Graham 2006). The American pika (Ochotona princeps, henceforth simply pika), a small mammal (order Lagomorpha) that resides in high elevation talus habitat in California, has emerged as a model organism for studying the effects of climate change on montane small mammals (Beever et al. 2011, Erb et al. 2011, Stewart and Wright 2012, Jeffress et al. 2013). Pikas are well adapted to surviving cold winters under the snow, but evidence suggests they may be highly vulnerable to increases in summer temperature. Historical revisit studies in the Great Basin (Beever et al. 2011) and California (Stewart et al. in review) both indicate that summer temperature is the best climate predictor of extirpation. Models that predict pika occupancy as a function of summer temperature project that pikas could become extirpated from > 90% of their current habitat in California by the end of the 21st century (Calkins et al. 2012, Stewart et al. in review). The Pikas poor capacity to dissipate heat physiologically (MacArthur and Wang 1973) appears to force them to thermoregulate behaviorally, spending more time in underground and less time active above ground (Smith 1974) when high diurnal temperatures occur. The central hypotheses of this study is that heat stress results in (H1) reduced above ground activity, (H2) reduced ability to forage (e.g. energy budgets), and (H3) reduced fitness. While inductive reasoning supports these hypotheses, they have not yet been tested empirically. In addition to testing mechanisms of climate-mediated decline, a key goal of this proposal is to parameterize a model of pika demography and distribution that will give insight into the thresholds that lead to population collapse. Location: This study will be conducted at the talus fields of Carpenter Ridge, located at the Sagehen Field Station, north of Truckee, CA. The study will benefit from a weather station located on Carpenter Ridge and limited public access to the study site. Carpenter Ridge is located at sufficiently low elevation (8,500) that pikas are likely to experience adverse effects from daytime temperature during much of July and August (personal observation). Carpenter Ridge is located at sufficiently high elevation to support a self-sustaining pika population, with an adequate numbers of pikas to ensure the feasibility of the study (surveys conducted at Carpenter Ridge in 2011, 2012, and 2013). Behavioral Observations: I will use camera traps (Reconyx PC900) to observe pika behavior. Pikas are central place foragers and each camera will be aimed to capture activity at the center of the pikas territory. Camera traps are ideal for this application because they have minimal impact on animal behavior in contrast to observations from nearby humans. Because camera traps use IR-imaging to record behavior after dark they can be used to assess whether pikas are able to escape the constraints of daytime thermoregulation by foraging at night. During a period of human observations, the mass of plant matter collected orconsumed will be estimated in-situ, and samples will be collected forlaboratory measurement of energetic and water content. Previous Pilot Study: During September of 2013, I piloted this study by collected pika behavioral data paired with environmental measurements. My main conclusion from this effort was that camera traps are more effective than humans at measuring relative activity levels of pikas. Environmental Heat Flux Measurements: To directly measure the thermal environment that pikas experience I will instrument the study site to measure environmental heat flux (e). e is a measure of the rate at which an animal looses or gains heat from its environment. To maintain homeostasis, the sum of e and metabolic heat gain must be equal to zero. Pikas commonly experience heat loading during foraging drips (e.g. slight increase in body temperature), followed by heat dumping (slight decrease in body temperature) when they go underground between foraging trips (Macarthur and Wang 1974). To measure the full range of environmental conditions I will measure e at the following locations: (i) on forefields where pikas forage, (ii) on the surface of the talus, and (iii) in the cool interstitial cavities below the talus surface. I will measure e by deploying fur-covered, copper-framed operative temperature models, designed to mimic the size, shape, and thermal properties of a pika. Operative temperature models, have been used for over 30-years (Dzialowski 2005) and have been shown to accurately predict body temperature in ectotherms and environmental heat flux in endotherms (Dzialowski 2005, Sinervo et al. 2010). Because operative temperature models mimic the physical properties of an animal and are deployed directly to the animals environment, they effectively distil multiple environmental measurements (e.g. ambient temperature, direct solar insolation, wind speed, and relative humidity) into a single measure of the effect they have on thermoregulation.

Visit #34103 @Sagehen Creek Field Station

Approved

Under Project # 28268 | Research

Mapping the pika's thermal environment though space and time

graduate_student - University of California, Santa Cruz

Reservation Members(s)

Joseph Stewart Jun 15 - 16, 2014 (2 days)
Joseph Stewart Jun 15 - 16, 2014 (2 days)

Reserve Resources(s) | Create Invoice

Camping 1 Jun 15 - 16, 2014
Camping 1 Jun 15 - 16, 2014