Persistence of low-elevation pikas: climatic and other influences
Loss of pika populations from lower elevations and latitudes, such as the loss of nearly 30% of interior Great Basin populations recorded during the 20th century, is consistent with losses that have occurred over the last 14,000 years (Grayson 1993). Given the recent extirpation of pikas from low-elevation sites within 150 km (93 mi) of Lava Beds (Beever 1999; fig. 2), current persistence of pikas in Craters and Lava Beds National Monuments is noteworthy. Although population losses in the Great Basin occurred not surprisingly at sites that were drier and warmer than those at which populations persisted, estimated climates at Lava Beds and Craters were notably drier and hotter than even those locations in the Great Basin where pikas have been recently extirpated. However, the tubes, caves, and deep, complex lava formations that occur across both monuments undoubtedly provide pikas with relatively cool refugia during times of heat stress. Interestingly, though, pikas were not exclusively confined to caves and lava tubes during my July surveys, suggesting that temperature influences provide only a partial solution to the mystery of how pikas persist in these monuments. Pika behavior plays a substantial role in mediating the effects of thermal stress, and measuring temperature regimes that pikas experience throughout the day and across seasons may provide another clue to understanding how they persist in these low-elevation areas.

“Pika behavior plays a substantial role in mediating the effects of thermal stress....”

Table 1: Locations sampled for pikas in Lava Beds and Craters of the Moon National Monuments, July 1995.