Abstract
The signature whistle of the Atlantic bottlenose dolphin (Tursiops truncatus) is a well-studied acoustic signal know for broadcasting identity and maintaining contact with conspecifics. Several studies have investigated the use of this signal surrounding the birth of calves to dolphin social groups, although there appears to be discrepancies between the findings of these studies. We aimed to add to the current literature in an attempt to reconcile some of these inconsistencies through investigation of signature whistle production by a bottlenose dolphin group two months prior to and two months following the birth of a calf to one of the social group members. We found that the production of signature whistles matching the contour belonging to our dolphin mother increased significantly in both the pre- and post-partum period. Heightened production of the mother’s signature whistle type in the first week of our focal calf’s life supports the establishment of a recognition system within this time period. Given that learning processes associated with the sound environment appear to begin shortly after calf birth, we also explored the signature whistle rates of the other social group members in an effort to determine whether any signature whistle production influenced the development of the dolphin calf’s own signature whistle type. We found that the signature whistles of the other social group members were significantly lower than production of the mother’s signature whistle until after the first week post-partum. None of the signature whistle types appeared to influence the signature whistle development of our focal calf within the scope of this study, however, as the calf did not develop a signature whistle in her first two months of life.
Highlights
The signature whistle of the Atlantic bottlenose dolphin (Tursiops truncatus) is a well studied acoustic signal known for broadcasting identity and maintaining contact with conspecifics
Given that learning processes associated with the sound environment appear to begin shortly after calf birth, we explored the signature whistle rates of the other social group members in an effort to determine whether any signature whistle production influenced the development of the dolphin calf’s own signature whistle type
It has been hypothesized that these pre-partum increases in maternal signature whistle production may aid in calf recognition of this sound shortly after birth by exposing the calf to the sound in utero (Kuczaj & Winship, 2015; Mann & Smuts, 1998; Mello & Amundin, 2005), but later studies have found no evidence substantiating this phenomenon in the pre-partum period (Fripp & Tyack, 2008; King, Guarino, Donegan et al, 2016)
Summary
The signature whistle of the Atlantic bottlenose dolphin (Tursiops truncatus) is a well studied acoustic signal known for broadcasting identity and maintaining contact with conspecifics. These later studies reported heightened production of the mother’s signature whistle in the weeks immediately following calf birth (Fripp & Tyack, 2008; King, Guarino, Donegan et al, 2016) This increased post-partum production of the mother’s signature may be an underlying mechanism in the establishment of an early recognition system in the mother-calf dyad (Fripp & Tyack, 2008; King, Guarino, Donegan et al, 2016), but there appears to be some variability in the sensitive window during which this process occurs. Given the findings presented by King, Guarino, Donegan et al (2016), it is more likely that learning influences the establishment of an early recognition system within a mother-calf dyad more so than imprinting, the underlying mechanisms for both need not be mutually exclusive
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