Rhythmic dimension in the echolocation click trains of sperm whales: a possible function of identification and communication

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Authors: André, Michel, Kamminga, Cees
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2000
• Subjects: Rime; Physeter macrocephalus; Sperm whale
• Online Access: http://dx.doi.org/10.1017/s002531549900168x; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002531549900168X

Fourier spectral analysis was used to highlight a rhythmic dimension of the click repetition pattern of the sperm whale ( Physeter macrocephalus ). Analysis of numerous series of regular clicks only showed occasionally the previously described codas used for communication. Out of a sample recording of vocalizing sperm whales, an apparent cacophony, belonging to a year-round resident group foraging a few miles off the coast of Gran Canaria, the individual click sequences of four animals have been unravelled by cross-correlating their time wave shapes. The Fourier spectrum, which yields the harmonic aspects of each isolated click sequence, shows a deterministic structure that appears as a strong modulating frequency. This shows that click production is not a random process and possibly characterizes, in fact, a signature of the animal. Here we introduce a new concept: this rhythmic modulation represents the acoustic signature of each individual sperm whale, which we have called RIME (rhythmic identity measurement). The RIME would allow a whale to distinguish its own echo time pattern from the background of other click trains during echolocation. The RIME appears to represent a new concept in communication strategies and might also be present in other-social-odontocete repertoires.