Patterns of Selective Caching Behavior of a Generalist Herbivore, the American Pika (Ochotona princeps)

Abstract

Caching decisions have been studied for many species, but large-scale variation of selective preferences due to environmental heterogeneity has rarely been examined. We investigated large-scale patterns of selective caching behavior in the American pika (Ochotona princeps), a non-hibernating generalist herbivore that caches vegetation in haypiles to serve as winter food. At 13 sites throughout the southern Rocky Mountains, we identified the three most common available and cached plant species and analyzed them for dietary quality. Selectivity at each site was measured as the difference between average quality of the most common cached and available vegetation. Pikas consistently cached materials of higher quality than the most common available vegetation. Selectivity for high nitrogen corresponded to quality of available plants and site summer temperature, whereas selectivity for high water content was negatively correlated with elevation. Our results indicate that pikas cache a variety of plant materials while using different selectivity cues, illustrating the complexity of pika caching behavior across a range of environmental conditions and forage values. Future studies on caching behavior should take into account differential selectivity due to environmental heterogeneity.