Social Behaviour of the Arctic Ground Squirrel, Spermophil Us Und Ulat Us

Abstract

1. Social behaviour and group organization of arctic ground squirrels (Spermophilus undulatus) enclosed in an outdoor courtyard were studied during two years. Common social behaviour patterns are described. Serial and simultaneous release experiments were used to study interactions among small groups of squirrels. Frequencies of some acts were recorded, and a quantitative method was developed to describe the extent of interaction among animals. 2. In each experiment one or more squirrels was strongly territorial around an exclusive burrow. During agonistic encounters pairs of animals used a variety of mutual pushing postures, some of which tended to occur in a typical sequence. When both sexes were present, males acquired territories before females did. 3. In simultaneous release experiments the heaviest animals established territories first. In serial release tests the first animal to acquire a territory usually maintained it regardless of the size of individuals released later. 4. Greater territorial success among larger, longer-established, and hence more socially experienced ground squirrels may increase the probability of successful rearing of young in an environment where mortality is heavy among animals unable to secure and maintain burrows in favorable habitat.