Abstract
For dolphins, the strongest bond documented is typically that between a mother and her pre-weaned offspring, but outside of the maternal relationship, our knowledge of calf behavior is limited. We examined how 23 bottlenose dolphin (Tursiops truncatus) calves (11 females and 12 males from 9 matrilines) initiated pectoral fin contact (PFC) exchanges with their mothers and kin (n = 362) versus with non-kin (n = 950). Calves initiated PFC exchanges with preferred partners (primarily their mothers) over individuals who were simply available to them. For calves with mothers as their only kin available, there was a difference in how they shared PFC with non-kin adults versus non-kin young. A calf was twice as likely to initiate PFC with an adult (mother or adult non-kin) as with another young dolphin. Male and female calves were different in how they initiated PFC with kin and non-kin, which supports previous research that identified a sex difference in calf behavior. These results support the observation that kin and non-kin dolphins share PFC differently. It is also likely that kin (mothers and calves, siblings, etc.) use other forms of contact to share information and potentially develop their relationships. Understanding all types of tactile contact would facilitate a more detailed understanding of how touch might be used by dolphins when relationships are established and maintained.
Highlights
For most social mammals, the strongest bond documented is that between a mother and her offspring (Hinde, 1970), and this is potentially true for dolphins as well (Gubbins et al, 1999; Mann et al, 2000; Mann & Smuts, 1999)
Dudzinski et al 377 focused on calf associates to examine how bottlenose dolphin (T. truncatus) calves interacted with kin and non-kin peers and found variability ranging from none to several associates with both kin and non-kin conspecifics
The majority of historic and current literature related to preferences in tactile exchanges between sibling versus non-sibling conspecifics is for primate research (Janus, 1989; Kapsalis & Berman, 1996; Schino, 2001; Silk, 2002; Wu et al, 2018), the mangrove killifish (Kryptolebias marmoratus) preferentially associate with kin over non-kin and show less aggression toward related conspecifics (Edenbrow & Croft, 2012)
Summary
The strongest bond documented is that between a mother and her offspring (Hinde, 1970), and this is potentially true for dolphins as well (Gubbins et al, 1999; Mann et al, 2000; Mann & Smuts, 1999). Utilizing a four-year subset of the current study’s data during which more non-kin than kin peers were available to the seven calves observed, Levengood and Dudzinski (2015) found that three calves preferred kin while the other four showed no bias These results suggested that outside the mother-calf bond there was no conclusive preference between kin and non-kin associates. Cappiello et al.’s results were observed for rhesus monkeys three decades earlier by Janus (1989); these primates played with kin and non-kin but preferred same-aged non-siblings more than other non-siblings Even given these studies on dolphin calf play behavior, there is a paucity of data on how calves use tactile contact during play, or during other contexts
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