Behaviour 2019
Amplitude Contours Of Signature Whistles Are Non-Stereotyped But Show Patterns Of Declination
Brittany Jones, Samantha Tufano, Risa Daniels, Sam Ridgway. National Marine Mammal Foundation, San Diego, CA, United States

Bottlenose dolphin signature whistles are characterized by a distinct pattern of frequency modulation over time. These stable frequency contours are known to broadcast individual identity to conspecifics. However, little is known about the amplitude modulation patterns across signature whistles. We examine the amplitude-time contour of signature whistle emissions from eight dolphins in the U.S. Navy Marine Mammal Program. Although the amplitude contours are more highly correlated within individuals than between, they are largely variable across whistles, even from the same producer. frequency is negatively related to relative whistle amplitude (r = -0.49) and there is a significant quadratic relationship characterized by a rise and fall pattern of relative amplitude distribution over the course of all signature whistles. While the frequency-time contour remains individually distinct, flexibility in the amplitude contour may be an avenue for encoding additional information. The fade-in, fade-out pattern of energy distribution may be a useful cue for managing antiphonal whistle exchanges. These findings suggest that amplitude modulation is salient in signature whistles.