When mum's away: a study of mother and calf ego networks during separations in wild bottlenose dolphins (Tursiops sp.)

Early social development in long-lived social mammals has important implications for adult behaviour, particularly in taxa that exhibit stable long-term bonds. In one such species, bottlenose dolphins, calves have precocious locomotion, enabling them to separate from their mothers soon after birth and associate with other dolphins in the absence of direct maternal influence. To investigate mother and calf social patterns while together and separated, we analysed the ego networks of 27 mother-calf pairs constructed using group composition data from focal follows and evaluated differences based on calf sex. When separated, all calves had larger, less dense ego networks than their mothers, whereas ego networks of mother and calf when together were similar in size to those of calves, but significantly less dense. Most intriguingly, during separations, male calves' relationships with other male calves were stronger than expected, foreshadowing the long-term bonds between adult male alliance partners. Female-female calf relationships were not stronger than expected, but when together, mothers and female calves had strong relationships with juvenile females. These results support the social bonds hypothesis and suggest that temporary separations allow calves to build and strengthen their social networks. Since bottlenose dolphins show bisexual philopatry and infant relationships can persist into adulthood, calf independence and early social development probably have implications for future success. (C) 2011 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.