Ecology and Social Behavior of Golden Marmots (Marmota caudata aurea)

Abstract

We studied golden marmots (Marmota caudata aurea), a little-studied, hibernating Eurasian sciurid, for 6 years at Dhee Sar, Pakistan, to evaluate their social behavior in light of existing thoughts about social evolution of marmots. Golden marmots most commonly were found in apparently monogamous associations (37/89 social groups consisted of one adult male and one adult female) but lived in larger groups containing up to seven adults, where group members shared a common home range and burrow system. When multiple adults lived together, contrary to the typical sciurid pattern, they lived in male-biased social groups. When multiple adult females shared a home range, only a single female in a given group lactated and weaned young. Reproduction was infrequent; >80% of social groups failed to wean a litter in any given year. Golden marmots delayed leaving their natal home range until after they had reached adult body size (2::3 years old) and were presumably sexually mature. Groups with mUltiple adults were largely a consequence of delayed dis­ persal. Resident marmots commonly tolerated adult immigrants. Golden marmots hiber­ nated socially; the active season of all members of a group was identical. Overwinter mortality of juveniles (30%) was higher than that of yearlings or adults « 10%). Some evidence of benefits from social hibernation was found; juveniles hibernating with only parents and littermate siblings suffered lower overwinter mortality than juveniles hibernat­ ing with other individuals. While general predictions about sociality in marmots were up­ held, an economic model combining defense costs and resource distribution failed to ex­ plain the mechanism of social monogamy.