Do bottlenose dolphins display behavioural response to fish taste?

Abstract

The chemosensory abilities (i.e. taste, smell and trigeminal perception) of odontocete cetaceans are still widely unknown. However, a better understanding of their potential use of these senses would not only improve our knowledge of their behavioural ecology, but also allow us to develop behavioural enrichment strategies for captive odontocetes using sensory stimulation. While studies on taste bud anatomy and taste receptor genes in these animals have provided useful information, ultimately behavioural experiments are crucial to assess whether odontocetes use their sense of taste in water. Go/no go and conditioning experiments in bottlenose dolphins (Tursiops truncatus) have previously shown that they can perceive basic tastes, but it is still unclear whether they are able to detect food-related chemical mixtures. We thus designed a spontaneous choice experiment using floating taste diffusers in order to test whether captive bottlenose dolphins could detect and display attraction behaviours towards a natural fish taste stimulus. Four dolphins, two adult males and two juvenile females, were involved in the experiment. Our results show that the juvenile females interacted with the fish taste diffuser significantly more than with the control. However, the adult males did not seem to make a clear choice. Also, the juvenile females showed a significantly greater level of motivation towards the test, spending more time interacting with the diffusers and holding them in their open mouth more often than the adult males. These findings corroborate previous behavioural studies suggesting that taste perception is functional in bottlenose dolphins, at least in young individuals. They also suggest that the taste of their natural prey could be attractive to them. Finally, the methodology used in this study proved to be easy to implement in captive odontocetes and will allow for investigating further their use of taste in feeding and social contexts without the need for conditioning experiments that require long periods of training. This experimental design could also be included in behavioural enrichment initiatives in captive marine mammals.