Most hikers who frequent the local alpine crags are familiar with one of the more endearing mammals of our area. Pikas are more often heard than seen, giving their short, shrill alarm distinct to the high mountains. If you stay still long enough and have keen eyes, you’ll find them looking out from talus pile hideouts watching nervously for trouble.
Pikas are lagomorphs, kin to rabbits and hares, and not rodents. They probably reached their zenith as a family sometime in the Pleistocene, aided by the cooler northern temperatures. They are well adapted to survive frigid mountain winters, but are highly susceptible to heat stress in temperatures over 27ºC. Today, the few species remaining are found mostly in Asia. Two are here in North America. The American Pika is found from central California and northern New Mexico, north to the Prince George area. The Collared Pika is farther north throughout most of Yukon and eastern Alaska. While there may be few species of pika, there have been 18 sub-species of American Pika identified. This reflects their highly isolated populations and minimal dispersal abilities. Pikas are strongly associated with talus slopes, where they make their homes and seek refuge from predators, that are adjacent to grassy meadows where they forage for food. This specific habitat requirement limits them to alpine areas and crossing the forested landscape between their preferred habitats is not an easy task. Life as a dispersing, juvenile pika is not easy.
Their habitat is best viewed as ‘islands’ in a sea of inhospitable forests which isolates one group of pikas from the neighbouring alpine area. Their population ecology is an excellent fit of Island Biogeography theory that I discussed in my last column. Rather than number of species however, the question is the number of individuals. Smaller alpine ‘islands’ will support fewer individuals, which will leave them susceptible to random environmental effects such as poor weather which may wipe out an entire year’s reproduction effort. Smaller populations are more vulnerable to disease, genetic inbreeding and other impacts.
Once a population is lost, the empty habitat can only be recolonized by other pikas that manage to cross the inhospitable forested sea. The more isolated a population is from other pikas, the less likely it is to experience successful immigration.
Their patchy distribution today is a remnant of the last ice age, when more continuous populations are thought to have occurred throughout western North America. Research backs this up, with evidence of pikas from the late Pleistocene in areas where they no longer exist. The average elevation of now extinct pikas 8 to 10 thousand years ago was 1750 m, while today pikas in the same area of the US Great Basin occur at an average elevation of 2530 m.
Research on prehistoric pika populations suggests their extinctions were driven by increasing temperature, decreasing moisture and changes in plant communities. These three conditions are all key predictions of current climate change models, which does not bode well for pikas. However, last week the US Fish & Wildlife Service released their review of the American Pika in the USA in which they determined that, though climate change may impact the small lagomorphs, they are not currently at risk under US Endangered Species legislation.
Hopefully the same holds true here in BC. If American Pikas do decline under predicted climate change conditions, their populations will likely contract toward the cooler north. This would make BC responsible for an increasing proportion of the species’ global range.
Farther north there is more concern. Biologists have documented significant declines in Collared Pika numbers in the Yukon leading the committee responsible for assessing status of endangered species in Canada (COSEWIC) to launch a review of the species and whether it merits listing under our federal Species at Risk Act.
Hopefully pikas will continue to find a way to persist should their alpine habitats continue to shrink upslope and northward. Talus slopes can be barren, unfriendly grey places. A little company is always welcome.
The pika picture above is by Dave Sindholt, a Cranbrook naturalist, who sent me the picture after reading the column. Thanks Dave! Great shot!
