Animals communicate important information by making sounds. Studying animal communication may provide clues about how they are feeling. Scientists from the University of KwaZulu-Natal, Stellenbosch University and NGO Sea Search Research and Conservation (aka Sea Search) have been investigating what important information might be hidden within dolphin whistles. The findings published this week in PLOS ONE focused on ten dolphins housed at uShaka Sea World, Durban.
The scientists discovered that the dolphins were almost entirely silent overnight, however in the morning when the animal care team arrived and particularly at feeding time, some dolphins became incredibly chatty. Dolphin calls are difficult to hear in-air, so scientists used underwater microphones, called hydrophones, to listen to the dolphins communicate. They found that certain individuals became particularly excited while waiting for food or being fed and the dolphins would whistle their signature whistle repeatedly, which is like calling out their own name. The study provides important insight into the emotions of dolphins and how underlying behavioural states, such as excitement or calmness, can be determined using acoustic monitoring. Now that we have baseline understanding of each dolphin’s whistling behaviour, any changes in could potentially be linked to a change in the wellbeing of the animal.
This study was led by PhD candidate Rachel Probert from the University of KwaZulu-Natal and practically supported by the animal care specialists at uShaka Sea World. Rachel’s research focuses on the acoustic communication of bottlenose dolphins around southern Africa, particularly how dolphins use whistles in different situations to relay information like caller identity and emotions. She says: “We know that common bottlenose dolphins use individually distinctive signature whistles to communicate, however there is no universal rule as to how each individual uses its signature whistle. Seeing this high individual variability from the dolphins at uShaka emphasizes the importance of considering and monitoring dolphins as individuals.”
Dr Tess Gridley, Honorary Senior Lecturer at Stellenbosch University and co-director of Sea Search specializes in dolphin communication. Dr Gridley and co-author Dr Simon Elwen, Research Associate at Stellenbosch University and co-director of Sea Search, first started working with uShaka Sea World in 2009 where they have been documenting the signature whistles of the dolphins held in this facility. Dr Gridley says: “There are two species of bottlenose dolphins and uShaka houses both as well as hybrids, making this a unique facility. The dolphins’ whistles have remained remarkably similar over the last 12 years, and this allows us to track which dolphins are calling at any one time and to use sound recordings to help understand their feelings and wellbeing.”
Gabrielle Harris, Welfare and Behaviour Management Curator says: “uShaka Sea World has an animal welfare focus that is multifaceted. The animal care specialists spend time doing daily assessments using common indicators such as respiration rates, appetite, health indicators such as weight and body condition as well as assessments of their behaviour. Scientists such as Rachel, Tess and Simon are welcomed. As part of uShaka Sea World’s welfare imperative, this work helps to ensure progressive understanding of animals in human care and assists us in our conservation efforts”.