JACKSON, Wyo. — Newly released research on American pikas suggests that, although average summer-long temperatures still strongly predict where pikas do versus do not currently occur, chronically cold temperatures in winter and retention of snowpack best predict patterns of pika occurrence.
The peer-reviewed paper was published in late November and incorporates the more complete information of where the species used to occur. The research focused on American pika populations in four geographic sub-regions of the mountainous habitat in the southern Rocky Mountains in New Mexico: the Jemez Mountains, the San Juan Mountains and the northern and southern Sangre de Cristo Mountains. During 2016–2020, 570 independent patches of talus, or rock piles that can accumulate at the base of cliffs or steep slopes, were surveyed.
Erik Beever, who’s been researching American pikas across the western U.S. since 1994 in 16 different regions, is an author of the new paper. Beever tells Buckrail that, where the pikas in northern New Mexico are considered to be on “the trailing edge” of the species geographic distribution, both northern New Mexico and Greater Yellowstone Ecosystem (GYE) pikas are Rocky Mountain populations.
However, since 2010 there have been five lineages of American pika identified. A sixth was added in 2024; of the six, three lineages are in the Rocky Mountains. The GYE pika population is distinct from the Southern Rockies pikas, and a 2024 range-wide study of pika genetics reported that they’ve been on different trajectories for around 2.3 million years.
Binary modeling across several studies previously suggested average summer temperatures were the most important factor of pika occurrence when examining where pikas are currently present versus where they were not. But the new research suggests that chronically colder conditions likely benefit pikas “by retaining the insulative and water-providing snowpack for longer durations.” This research divided the “not currently occupied by pikas” category into both “previously occupied” and “no evidence of occupancy,” and analyzes patterns of the three ordered occurrence states.
Ordinal modeling as an approach, used in this newest work, hasn’t yet been applied to pika research in the GYE, but the results from New Mexico could still be useful in understanding pika distribution locally.
According to Beever, having three categories rather than just two “provides a richer story for future forecasting” of pika occurrence, or where pikas are likely to be found as the climate changes.
“This distinction may well shift forecasts for a ton of different species,” Beever say.
In terms of applicability and relevance to other species, Beever points to many species’ modifications of the local landscape as being useful in ordinal modeling going forward. This could include nests, burrows, bark chewing, beaver lodges, tree stumps, fossils, bones and more. Examples of a species’ past occurrence in an area despite no longer being present for varying amounts of time include nests, burrows, owl pellets, feces, bark chewing, beaver lodges, woodrat middens, tree stumps, fossils, environmental DNA and more.
In the case of pikas, Beever says surveyors can surmise that pikas were previously present, even when their unique calls and fresh haypiles are not found in a given survey, by finding old haypiles, old fecal pellets or both.
Beever also notes that analysis of pika surveys from multiple management units in the GYE between 2014 to 2016 and 2019 to 2021 will appear in forthcoming publications.
