Vocal learning is a rare skill in mammals. Little is known about how flexibly dolphins use vocal learning as a result of social interactions. To investigate this flexibility, we examined the whistles of a female Risso’s dolphin, that was orphaned at an early age and raised in a group of six bottlenose dolphins in the Oltremare marine park in Italy. We used a four-hydrophone array to localize where calls came from using time-of-arrival difference analysis. From a total of 50 hours, we analysed all segments where one animal was isolated from the group by choosing to swim alone in one of three holding pools. Each animal produced primarily one whistle type when in isolation. We collected 8 to 40 of these 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. A discriminant function analysis (DFA) with cross-validation was performed on the components from a principal components analysis. The DFA correctly classified the emitter in 84% of the cases. The Risso’s dolphin whistles formed a distinctive cluster within the range of Tursiops signature whistles. Seven parameters could be compared with published values from wild Grampus populations (Rendell et al., 1999). Average values for start, end, minimum and maximum frequency as well as bandwidth of the captive Risso’s dolphin whistles were considerably closer to the averageTursiopswhistle from its pool than to wild Grampus whistles. Only in mean frequency did the captive Grampus match the values of wild Grampus. Whistle duration in the captive Grampus was considerably longer than in Tursiopsand wild Grampus. Our results provide evidence for the presence of signature whistles in a Risso’s dolphin and suggests that Risso’s dolphins can adjust their communication signals to vocal templates in their environment.
Signature whistles in a Risso’s dolphin (Grampusgriseus) housed with bottlenose dolphins (Tursiopstruncatus): evidence for vocal learning
FAVARO, LIVIO;
2011-01-01
Abstract
Vocal learning is a rare skill in mammals. Little is known about how flexibly dolphins use vocal learning as a result of social interactions. To investigate this flexibility, we examined the whistles of a female Risso’s dolphin, that was orphaned at an early age and raised in a group of six bottlenose dolphins in the Oltremare marine park in Italy. We used a four-hydrophone array to localize where calls came from using time-of-arrival difference analysis. From a total of 50 hours, we analysed all segments where one animal was isolated from the group by choosing to swim alone in one of three holding pools. Each animal produced primarily one whistle type when in isolation. We collected 8 to 40 of these 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. A discriminant function analysis (DFA) with cross-validation was performed on the components from a principal components analysis. The DFA correctly classified the emitter in 84% of the cases. The Risso’s dolphin whistles formed a distinctive cluster within the range of Tursiops signature whistles. Seven parameters could be compared with published values from wild Grampus populations (Rendell et al., 1999). Average values for start, end, minimum and maximum frequency as well as bandwidth of the captive Risso’s dolphin whistles were considerably closer to the averageTursiopswhistle from its pool than to wild Grampus whistles. Only in mean frequency did the captive Grampus match the values of wild Grampus. Whistle duration in the captive Grampus was considerably longer than in Tursiopsand wild Grampus. Our results provide evidence for the presence of signature whistles in a Risso’s dolphin and suggests that Risso’s dolphins can adjust their communication signals to vocal templates in their environment.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
