Summary:

In this project, the variability in whistles from mother and calf bottlenose dolphin pairs from Shark Bay in Australia was investigated.  The results showed that the whistles of the same mother and calf pair showed wide variability, and different pairs shared similar whistles.  How these results relate to the idea that bottlenose dolphins have "signature whistles" is discussed. This project was expanded and presented as a poster at the 2005 Society for Marine Mammalogy biennial conference in San Diego.  The full poster abstract is below.

 

Full abstract:

 

A Quantitative Analysis of Whistle Variability found in Mother-Calf Pairs of Bottlenose Dolphins in Shark Bay, Western Australia

 

Harris, Danielle(1), Janik, Vincent M.(1), Mann, Janet(2)

(1) Sea Mammal Research Unit, School of Biology, Gatty Marine Laboratory, University of St. Andrews, St. Andrews, Fife KY16 8LB, UK
(2) Department of Psychology, Georgetown University, Washington, DC 20057, USA

NB: Affiliations are given as accurate in 2005.

Bottlenose dolphins (Tursiops truncatus) produce individually distinctive signature whistles that are used in individual recognition and group cohesion. This has been reported from a variety of captive facilities and from the wild. However, signal repertoires and variability may vary in different locations. Bottlenose dolphins in more sheltered and visually accessible environments may not have the same
requirements for an acoustic identification system as offshore animals. To test this hypothesis we investigated whistle variability between bottlenose dolphins in Shark Bay, Western Australia, and compared it with that found in Atlantic animals. We collected acoustic and nonacoustic behavioural data from a 10 m catamaran on 15 lone mother-calf pairs. Only seven of these produced sufficient whistles for further analysis. We traced the frequency modulation pattern of 169 whistles from these animals and compared them in a cross-correlation analysis that allowed time-warping of the extracted contours. The results showed that mother-calf pairs of Shark Bay dolphins do not differ sufficiently in their whistles to be identified individually by this analysis, while the analysis performed much better with the Atlantic individuals. Our results suggest that inter-individual whistle variability differs between populations. It is too early to identify the main reason for this difference. It might be rooted in the fact that Shark Bay provides very different habitats from the Atlantic Ocean. Another possible reason is genetic differences between populations.