Hey Baby: Signature Whistle Use Facilitates Calf Retrieval in a Female Bottlenose Dolphin, Tursiops truncatus (#4)
Bottlenose dolphins use vocal learning to develop individually distinctive signature whistles that allow for individual recognition. An important function of signature whistles is to allow mothers and calves to keep in acoustic contact and to find each other after a separation. Previous studies have shown that when wild mothers and calves are caught and temporarily separated, each makes its own signature whistle repeatedly, but occasionally copies the other's whistle as well (King et al., 2013; Sayigh et al., 1990). When yearling calves voluntarily separate from their mothers in the wild, they repeatedly produce their own signature whistle prior to a reunion (Smolker et al., 1993). However, there has been very little research on the vocal mechanisms a female dolphin may employ when she wants to reunite with her calf. In this study, we repeatedly asked an adult female dolphin to Go get (i.e., retrieve) her 3-month-old calf or Go get another object, while we recorded her vocal behaviour. The vocal response to the two trial types was significantly different (GLM, P = 0.0003). The adult female frequently produced her own signature whistle when asked to retrieve her calf, but rarely produced any such whistle when asked to retrieve an object. She also produced significantly more signature whistles when it took her longer to retrieve her calf (GLM, P = 0.0009). There was no evidence of the calf's signature whistle during either trial type. Our results therefore add to our current understanding of signature whistles by showing that they not only function in broadcasting identity, but are used by mothers to actively initiate reunions with their calves, thus highlighting the importance of maternal signature whistle use in facilitating mother-calf reunions.
- King, S. L., Sayigh, L., Wells, R., Fellner, W., & Janik, V.M. (2013). Vocal copying of individually distinctive signature whistles in bottlenose dolphins. Proceedings of the Royal Society B, 280, 20130053.
- Sayigh, L. S., Tyack, P. L., Wells, R. S., & Scott, M. D. (1990). Signature whistles of free-ranging bottlenose dolphins Tursiops truncatus: Stability and mother-offspring comparisons. Behavioral Ecology and Sociobiology, 26, 247-260.
- Smolker, R. A., Mann, J., & Smuts, B. B. (1993). Use of signature whistles during separations and reunions by wild bottlenose dolphin mothers and infants. Behavioral Ecology and Sociobiology, 33, 393-402.