Natal attraction: allomaternal care and mother–infant separations in wild bottlenose dolphins

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To determine whether allomaternal care occurs among bottlenose dolphins, we examined patterns of association and mother–infant separations for eight infants (164.4 focal h) during the first 3 months of life. During the first week of life, three inexperienced females (nullipara and mothers of infants that did not survive the newborn period) attempted to take infants from their mothers 13 times. Mothers responded by rapidly retrieving the infant and threatening the female. By the second week, mothers consistently allowed the same females to escort their infants to tens of metres away from them, suggesting that such separations were no longer risky, possibly because infants had imprinted on their mothers. To determine whether escorts benefited mothers after the first week, we compared maternal behaviour when infants were away from their mothers, but alone (solitary separations), to when infants were away, but with escorts (social separations). Mothers were less likely to forage and were more likely to engage in non-foraging activities (socialize, rest or travel) when infants were with young escorts (other dependent infants) compared with when infants were alone. When infants were with older (juvenile or adult) escorts, maternal activity did not differ significantly compared with when infants were alone. This result suggests that escorts did not benefit mothers by allowing them to forage. Inexperienced females that never raised an infant were more likely to escort newborns than were parous experienced females, supporting the ‘learning to parent’ hypothesis.