Population ecology of the American pika (Ochotona princeps) in an extreme environment

Alteration of native habitat through human disturbance is generally implicated as the predominant cause of decline in terrestrial biodiversity. Anthropogenic forces destablilize critical processes such as reproductive success and dispersal of individuals; how species will respond depends to a large extent on the plasticity of habitat use. In this vein, habitat specialists may provide valuable opportunities to understand how colonization succeeds (or fails) in novel environments. The American pika (Ochotona princeps) is such a habitat specialist, occupying montane regions in western North America. This species is recognized as vulnerable to anthropogenic impacts (e.g. climate change) due to intrinsic characteristics (e.g. low thermal tolerance, low dispersal capability) that make it susceptible to local extirpations. In the southern interior of British Columbia, in a region that features extreme temperature shifts, I compared a population of pikas inhabiting a partially reclaimed mine site, with those found close by in natural habitat. All told, I monitored a total of 174 pikas from 2012-2014 to compare survival, physical characteristics, dispersal and den site attributes. Through mark-recapture and radio-telemetry, I found comparable survival and dispersal rates of pikas and almost no detectable physical differences. Investigation of undertalus temperatures of den sites revealed that microhabitats within the rocks largely were decoupled from the regional macroclimate, providing evidence of microrefugia as a functional buffer against macroscale climate impacts. Rock size of 1m3 and cryptogamic cover on talus near den entrances were positively influential to pika survival, whereas winter temperatures < -10°C under the talus negatively impacted survival. This study provides a relatively parsimonious explanation of pika persistence in atypical environments; within an extreme thermal environment such as in my study region, pikas appear capable of utilizing portions of anthropogenic habitat via microrefugia, although future longevity in a changing climate remains unknown.