Social and ecological influences on dispersal and philopatry in the plateau pika (Ochotona curzoniae)

Benefits and costs of dispersal and philopatry of the social plateau pika ( Ochotona curzoniae) were studied on the Tibetan plateau for 3 years. Althou gh short-lived, plateau pikas live in cohesive family groups that occupy bu rrow systems in sedge meadow habitat Most (57.8%) plateau pikas were philop atric, and dispersal movements were extremely restricted. No juvenile femal es or adult pikas moved more than two family ranges between years; the grea test observed dispersal distances were by two juvenile males that moved fiv e family ranges from the family of their birth. Traversing unfamiliar habit at was not a cost of pika dispersal because most dispersers settled in fami lies that they could easily visit before dispersal. Dispersal movements app eared to result in equalization of density among pika families, an expected result if competition for environmental resources influenced dispersal. Ma les did not disperse to gain advantages in competition for mates, as eviden ced by their moving to families with significantly fewer females. Females, however, moved to families with significantly more males. Males provide abu ndant paternal care, and significantly more offspring per female survived t o become adults from families with more adult males per adult female. Evide nce concerning the influence of inbreeding avoidance on natal dispersal was indirect. Some males exhibited natal philopatry; thus some families had op portunity for close inbreeding. Males and females that dispersed had no opp osite-sex relatives in their new families. Philopatric pikas may have benef ited by remaining in families that exhibited low local densities, and philo patric females might have benefited from social cooperation with relatives.