Abstract and Summary
Adult spatial relationships and social organization in a marked population of alpine mammals, the pika (Ochotona princeps), were studied over a 3-year period in the Rocky Mountains of Colorado. Home range size, distances between centers of activity of dyads, and weighted overlaps of home ranges of dyads were used to define space use patterns. Disappearance and establishment of individuals reflected the temporal component of space use. Relative frequencies of foraging (haying and feeding), surveillance, and communication (short calling, long calling, cheek rubbing) behaviors were recorded. Social relationships among adults were defined by agonistic interactions (aggression) and affiliative behaviors (social tolerance, vocal duets, copulations).
Males and females occupied individual home ranges of equal size on talus, their obligate habitat type. Adjacent home ranges were normally occupied by pikas of the opposite sex. Replacement of home ranges was always by a member of the same sex as the previous occupant. A high degree of affiliative behavior was expressed between spatially contiguous heterosexual dyads. Aggression was greater among intrasexual than heterosexual dyads, and spatial overlaps among intrasexual conspecifics were less than among heterosexual conspecifics.
Ecological constraints, such as the distribution of food (primarily located in meadows adjacent to the talus) and the short summer reproductive season (placing a premium on early appropriately timed litter;;) have apparently led to a facultatively monogamous mating system. Males can neither monopolize essential resources sufficiently to attract several females, nor defend groups of females as social repulsion among females further increases their dispersion.