Distinctive vocalizations from mature male sperm whales (Physeter macrocephalus)

Abstract

Groups of sperm whales (Physeter macrocephalus) were tracked acoustically off the Galapagos Islands between February and April 1985. In total, 716 h were spent in visual or acoustic contact with the whales, during which time vocalizations were recorded for 5 min/h. Distinctive loud, ringing clicks, called "slow clicks," were highly correlated with the presence of mature male sperm whales. Slow clicks were distinguished from usual clicks by their slower repetition rate or interclick interval, their longer duration, and, usually the presence of intensity peaks at about 1.8 and 2.8 kHz. Between clicks of individual males (identified by photographs of natural markings), there were differences both in interclick intervals and in the pattern of emphasized frequencies. These differences, however, were not distinct enough to allow us to reliably distinguish one male's clicks from those of another. We hypothesize that slow clicks may be a sign of a mature or maturing male and may inform other sperm whales on the breeding grounds of its competitive ability and maturity.