CONCLUSION:

Overall, climate variables had a significant but small correlation with body mass, explaining about 6 percent of the variation at best. The evidence suggests that temperature is not as important in influencing pika body size as expected, especially winter temperatures. It appears that plant productivity and precipitation are the most important factors in estimating body size. This may be because more vegetation can support larger pikas, and smaller pikas can subsist in more arid, less productive environments better.

Pika populations exhibit different average body masses but this variation does not appear to be driven by the climate and environmental variables tested here. Instead, a database analysis of elevation records of specimens over time shows that pikas have been moving up in elevation over the past 110 years. This study suggests that pikas are moving up in elevation in response to climate change and warming temperatures, instead of adapting in body size. This may be a problem facing pikas, because they already live at high elevation. Retreating upslope may not be an option for some populations in the future, because they may run out of habitat, or “fall off the top of the mountain.” This would lead to reduced population size and even local extirpation.