Self-referent phenotype matching and long-term maintenance of kin recognition

Self-referential phenotype matching, or using one’s own cues as a referent for recognizing kin, is expected in species with multiple paternity or maternity to discriminate among full siblings and half-siblings, or in nepotistic contexts to accurately assess relatedness. It would also facilitate optimal inbreeding and outbreeding. Self-matching has been predicted for Belding’s ground squirrels, Urocitellus beldingi, yet previous work could not rule out the possibility that animals use family cues rather than or in addition to their own cues for recognition. After hibernation, U. beldingi recognize their littermates but not previously familiar nonkin. Kin templates, including cues of mother and littermates, may be maintained throughout life, or, they may be lost during hibernation with memories of unrelated individuals, in which case self-matching must be used to create a new template in the spring. Using a cross-fostering design, these two possibilities were tested with olfactory discrimination tests after ground squirrels aroused from hibernation. Yearlings recognized their siblings, but not fostermates they had been reared with since birth, demonstrating that kin templates are lost over winter and self-matching is used to recognize kin after hibernation. Results are discussed in terms of plasticity of kin recognition systems, the costs and benefits of maintaining social memories, and the contexts in which templates are updated.