| Summary: | The purpose of this study was to gain insight into the significance of sperm whale (Physeter macrocephalus) sounds by examining their relationship to behavioral and circumstantial variables. Whales were tracked continuously for periods totalling months, off the Galapagos Islands, Ecuador, and sperm whale vocalizations were recorded systematically. In addition to the usual clicks (long series with interclick intervals of about 0.5 s), creaks (clicks at high repetition rates), and codas (short, repetitive click patterns) previously reported in the literature, a new vocalization type was discovered--"slow clicks." These were found to be produced by mature males and were distinctively different from the females' usual clicks. There was a strong correlation between behavior visible at the surface and rates at which different types of vocalizations were heard. Codas were given in social situations of large "clusters" (whales swimming together within 100 m of another), whereas usual clicks were associated with feeding behavior, when whales were diving deeply and dispersed in smaller clusters. Codas were relatively rare, and could be categorized into 23 discrete, almost non-overlapping types according to number of clicks and proportional lengths of interclick intervals. Codas overlapped or followed one another according to type in a non-random way, and coda type "5" tended to initiate coda exchanges. The rate of production of different coda types varied with behavioral and circumstantial variables such as identified group, month, maximum cluster size, presence of male, but the specific details of these relationships were not clear. It is hypothesized that usual clicks function as echolocation, slow clicks as a sign of male maturity and competitive ability, creaks as echolocation and communication, and codas as a means of social communication which serves to maintain social cohesion within stable groups of females following periods of dispersion during foraging. Thesis (Ph.D.)--Dalhousie University (Canada), 1990.
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