Mateo, J.M. & Johnston, RE 2000. Retention of social recognition after hibernation in Belding's ground squirrels. Animal Behaviour , 59, 491-499.
The retention of social memory during long periods of separation, such as hibernation or migration, has not been well documented, despite evidence for long-term social relationships in migrating species or in long-lived sedentary species. The ability of captive Belding's ground squirrels (Spermophilus beldingi) to remember previously familiar individuals as well as litter-mates after nine months of isolation was investigated. Before hibernation young ground squirrels discriminated between odours of familiar and unfamiliar individuals, as shown by greater investigation of a novel individual's odour. The following spring, these yearlings did not respond differentially to odours of previously familiar and unfamiliar individuals, suggesting that memory for familiar conspecifics was lost during hibernation. In contrast, both female and male yearlings continued to discriminate between odours of litter-mates and previously familiar non-litter-mates. Thus, recognition of one class of conspecifics - close kin - was maintained during prolonged social isolation, but recognition of familiar, unrelated individuals was not. If re-establishment of familiarity is not costly or if adults rarely interact with the same individuals in successive years, then selection may not favour retention of individual memories of particular conspecifics over the winter. Even though males rarely encounter kin after dispersal, yearling males did recognize their siblings, suggesting that the relative costs of maintaining kin-recognition abilities year-round may be low. Possible mechanisms underlying the formation and maintenance of individual and kin recognition are discussed.