Whistle Use by Pair-Bonded Male Bottlenose Dolphins
By Stephanie Watwood, PhD
Woods Hole Oceanographic Institution

This past summer I defended my Ph.D. thesis from the Woods Hole Oceanographic Institution (WHOI) in Biological Oceanography. I spent four summers on Sarasota Bay collecting data on the behavior of male dolphins in the Sarasota community. Male dolphins form stable, long-term alliances comparable to long-term relationships formed by terrestrial species. The goal of this thesis was to determine the effect of the formation of these alliances on vocal development. Bottlenose dolphins develop individually distinctive whistles called signature whistles. I found that alliance partners have similar signature whistles, while non-partners do not. Whistle similarity seen in alliance partners mirrors group-specific vocal convergence in stable groups of birds and bats.

I also explored whether signature whistles function as contact calls by looking at the whistles that are produced by different social groups. An allied male produced signature whistles most often when separated from his partner and least often when with his partner. Signature whistles were also highly individually distinctive, and therefore well suited as contact calls, while other whistle types were not. Separations and reunions between alliance partners were examined to determine if whistles are used to maintain contact between partners. Most whistles recorded from separated males were signature whistles. The timing of whistle production was correlated with the timing of the maximum partner separation and the initiation of a reunion. Few whistles were produced as the partners separated. Therefore, whistles may initiate reunions between partners. This thesis demonstrates several general mechanisms that bottlenose dolphins use to locate and maintain contact with close associates. I hope to continue this work in the future, looking more specifically at how whistles change over time as social relationships change. This work was funded by the National Geographic Society, the National Science Foundation, WHOI Ocean Ventures Fund, National Institutes of Health, SERDP, Dolphin Quest, Chicago Zoological Society, WHOI Academic Programs Department, and ONR.