Vocal learning, the ability to modify one’s vocalizations in form after hearing a model sound, is a rare skill in mammals. Within the delphinids, bottlenose dolphins use vocal learning in the development of their individually distinctive signature whistles, and can learn to use novel sounds as labels for novel objects. However, we know very little about how flexibly dolphins use their vocal learning skills in social interactions. Similarly, it is unclear how the skills of bottlenose dolphins compare to other species. In this study we investigated the use of sounds in one female Risso’s dolphin that was orphaned at an early age and raised in a captive group of bottlenose dolphins. Acoustic recordings were collected over 30 days in April 2011 within the Oltremare (RN) facilities. We used a four-hydrophone array to localize where calls came from using time-of-arrival difference analysis. We collected 8 to 40 signature whistles from each of the six Tursiops and 192 from the Risso’s dolphin. Nine time and frequency parameters were measured on each whistle contour and used to perform a principal components analysis. We then use principal components with eigenvalues > 1 to perform a discriminant function analysis with cross-validation. The Risso’s dolphin whistles formed a distinctive cluster within the range of Tursiops signature whistles. Among the nine acoustic parameters measured, seven could be compared with published values from wild Grampus populations (Rendell et al., 1999). Our results provide evidence for the presence of signature whistles in a Risso’s dolphin and suggests that this Risso’s dolphin has adjusted its communication signals to vocal templates in its environment.
Signature whistles and vocal learning in a Risso’s dolphin (Grampus griseus) raised in a bottlenose dolphins (Tursiops truncatus) community
FAVARO, LIVIO;PESSANI, Daniela;
2011-01-01
Abstract
Vocal learning, the ability to modify one’s vocalizations in form after hearing a model sound, is a rare skill in mammals. Within the delphinids, bottlenose dolphins use vocal learning in the development of their individually distinctive signature whistles, and can learn to use novel sounds as labels for novel objects. However, we know very little about how flexibly dolphins use their vocal learning skills in social interactions. Similarly, it is unclear how the skills of bottlenose dolphins compare to other species. In this study we investigated the use of sounds in one female Risso’s dolphin that was orphaned at an early age and raised in a captive group of bottlenose dolphins. Acoustic recordings were collected over 30 days in April 2011 within the Oltremare (RN) facilities. We used a four-hydrophone array to localize where calls came from using time-of-arrival difference analysis. We collected 8 to 40 signature whistles from each of the six Tursiops and 192 from the Risso’s dolphin. Nine time and frequency parameters were measured on each whistle contour and used to perform a principal components analysis. We then use principal components with eigenvalues > 1 to perform a discriminant function analysis with cross-validation. The Risso’s dolphin whistles formed a distinctive cluster within the range of Tursiops signature whistles. Among the nine acoustic parameters measured, seven could be compared with published values from wild Grampus populations (Rendell et al., 1999). Our results provide evidence for the presence of signature whistles in a Risso’s dolphin and suggests that this Risso’s dolphin has adjusted its communication signals to vocal templates in its environment.
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