Kin recognition by phenotype matching in female Belding's ground squirrels

Abstract

Female Belding's ground squirrels (Spermophilus beldingi), that had been reared apart from each other, were observed in paired-encounter tests to determine whether exposure to nestmates' phenotypes during development had influenced their subsequent social discriminations. As a result of cross-fostering, test partners were (1) either unfamiliar sisters (reared apart) or unfamiliar, unrelated females, and were (2) either reared with each other's siblings (indirectly exposed to each other) or were not reared with each other's siblings (not indirectly exposed to each other). Regardless of relatedness, females that were indirectly exposed to each other were significantly less agonistic during tests than females not indirectly exposed to each other. This suggests that females learned something from their nestmates' phenotypes and later recalled what they had learned in order to distinguish between their nestmates' unfamiliar kin and non-kin. Furthermore, sisters that were indirectly exposed to each other were less agonistic than nonsisters that were indirectly exposed to each other. This was true even when the only kin phenotypes females had experienced during rearing were their own, which suggests that females may have compared unfamiliar phenotypes with their own, as well as those of their nestmates. Thus, the phenotypes that females encountered during rearing, both their nestmates' and their own, influenced their later social discriminations, probably by phenotype matching. Under this recognition mechanism, an individual forms a hypothetical `kin template' based on its own or its familiar relatives' phenotypes, and later compares the phenotypes of other conspecifics with the learned template.