Yellowstone National Park Pika (Make sure your sound is on) The pika (Ochotona princeps) is considered an indicator species for detecting ecological effects of climate change. While abundant in the Greater Yellowstone Ecosystem, pika numbers are declining in some areas of lower elevations in response to increased warming, which reduces their suitable habitat. While the recent US Fish and Wildlife Service review of the pika found no current need to list the species as threatened or endangered, pi