Maternal and Other Social Influences on Signature Whistle Structure of a Captive Group of Bottlenose Dolphins (Tursiops truncatus)

Abstract

Bottlenose dolphins (Tursiops truncatus) are social animals that use acoustics as a major method of communicating across a marine environment. They also live in fission-fusion groups and thus interact with many conspecifics over a lifetime. Individual dolphins have a signature whistle that functions as an identity call and serves to maintain group cohesion in murky waters or during reconciliation. Dolphins exhibit vocal learning and the signature whistle of a calf may be modeled after the whistle of their mother or another individual in the pod as they develop. Mother-calf pairs or other related animals sometimes have similar whistle types. Some research has reported that male offspring have a similar whistle contour to their mother, whereas the female offspring may not resemble the maternal call. The goal of this study was to assess the whistle similarities in a group of fourteen bottlenose dolphins living in a captive, open ocean facility, The Roatan Institute of Marine Sciences, off the coast of Roatan, Honduras. The pod included eight offspring of varying ages and sex and six mothers. Data was collected from a hydrophone multiple times a day during a one-week span, during training sessions and free-swimming times. Data was analyzed and categorized using two methods: 1) the parameters of whistles were measured using Raven Pro and 2) the contours, or overall shape, of whistles were categorized by human judges. Whistles were also arranged into an acoustic family tree to better visualize the whistle types of related dolphins