TERRITORIALITY, HAYPILE FUNCTION, AND ANTI-PREDATOR BEHAVIOR IN THE PIKA, OCHOTONA PRINCEPS (FOOD CACHING, ALARM CALLING).

摘要

Territoriality, haypile function, and the responses of individuals to terrestrial predators were investigated in 1979-1981 in a marked population of pikas (Ochotona princeps) in the Rocky Mountains of Colorado.;The function of haypiles was investigated using naturalistic observations and experimental field manipulations. Males and females stored the same amount of vegetation, and 72% of adult haypiles were constructed on previously used sites. During 1581 hours of observation, no hay stealing was observed, even when haypiles were removed. Pikas preferentially selected both edible and inedible unfamiliar items in a cache selection experiment. Existing literature on pika haypiles was reviewed, and results were discussed in relation to predictions from food caching models. It is suggested that haypiles may serve functions other than food.;The responses of individually marked pikas to terrestrial predators indicated that adults discriminated contexts in which predators were present from non-predator contexts by short calling more frequently and for longer duration. Adults responded differently to two types of terrestrial predators, weasels and pine martens. Pikas called less frequently to weasels, avoided them more, and delayed the initiation of calling more often to weasels than to martens. Differences in the effectiveness of these two predators suggest that pika responses may reduce an individual's risk of predation. Both males and females called in response to predators, and residents called more often than non-residents. Calls to predators may function to warn local residents, probably kin.;Short calls, cheek rubs and aggression were used as diagnostic indicators of territoriality. Seasonal changes in spatial relationships and behavior were evident. Both males and females showed increasing site tenacity, decreased overlap with neighbors, and constriction of space use as winter approached. The functional significance of territoriality was investigated by examining hypotheses about the disadvantages of group living. Data indicated that territoriality in pikas probably functions to reduce competition for valuable resources, particularly overwinter sites and food.