Post-birth separation affects the affiliative behaviour of kin in a pitviper with maternal attendance

Abstract

The relatedness of individuals can have pronounced effects on behavioural interactions, as engaging in mutually beneficial behaviours with kin can increase inclusive fitness. Parental care can be particularly important for kin discrimination in birds and mammals, but similar studies have not been conducted on species exhibiting more rudimentary forms of care. Maternal attendance of young is ubiquitous among viviparous temperate pitvipers, but the adaptive value of this behaviour has received little attention. We sought to determine if being deprived of a maternal attendance period as neonates altered how cottonmouths (Agkistrodon piscivorus Lacépède), a common North American pitviper, responded to kin vs. non-kin. We measured the affiliative behaviour of related and unrelated juvenile–juvenile and mother–juvenile pairs that had been allowed a maternal attendance period or had been separated since birth. We found that maternal attendance was not required for sibling or mother–offspring recognition, but did enhance female affiliative behaviour overall, and particularly that of sisters. In contrast, related juveniles that were separated at birth showed a reversal of the sex-specific affiliative behaviour observed in maternally attended juveniles. Post-birth separation had only a modest effect on mother–juvenile affiliative behaviour, and no effect on the strong affiliation between mothers and daughters. The patterns of affiliative behaviour observed in maternally attended snakes corresponded to patterns that have emerged from previous captive and field studies of pitvipers; however, the behaviour of juveniles separated at birth was atypical. Thus, it is possible that maternal attendance plays some role in the development of adaptive sex-specific and kin-directed affiliative behaviour in pitvipers.