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

Abstract

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 halfsiblings, 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. 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Accurate discrimination of conspecifics according to genetic relatedness is a crucial prerequisite for nepotistic behaviours and facilitates mate choice to optimize inbreeding versus outbreeding. The adaptive significance of kin recognition in these contexts has been extensively studied (Bateson 1983; Hamilton 1987), yet complementary knowledgeof the proximate mechanisms bywhich animals recognize kin is lacking. Kin recognition is an internal process of assessing genetic relatedness that is inferred by kin discrimination, the observable differential treatment of conspecifics based on cues that vary with relatedness. An understanding of kin recognition involves three components: the production of unique phenotypic cues, or ‘labels’, the perception of these labels and their degree of correspondence with a ‘recognition template’, or a stored representation or memory of these labels (these two components are the mechanism of recognition), and the action taken by an animal as a function of the similarity between its template and an encountered individual (Beecher 1982; Sherman &