Strategy of Food Plant Selection in the Siberian Northern Pika, Ochotona hyperborea

Abstract

The rock-dwelling pikas of Asia and North America are suitable model species for studying foraging strategies of small generalist herbivores, because they collect and store green parts of plants for winter. In the past, contents of these stores were subjected to numerous studies but researchers differed in opinions on selective versus opportunistic plant-gathering by pikas. We analyzed plant species composition and their shares (%) in caches and in surrounding habitats in six territories of Ochotona hyperborea in Siberian mountains. We applied Ivlev’s Electivity Index for assessing selectivity. We found that some plant species were evidently preferred and others avoided by caching pikas. Among the former, many were rich in secondary compounds, while among the latter, evergreen tuft-forming plants prevailed. Our data conform to earlier findings on selective foraging by the American pika Ochotona princeps, and prove great similarity in winter diet of both species. We discuss possible cues used by rock-dwelling pika species to choose which plants to collect, and suggest that their harvesting strategy is most economic in harsh high-mountain habitats.