'Pop' Goes the Dolphin: a Vocalization Male Bottlenose Dolphins Produce During Consortships

Studies of dolphin communication have been hindered by the difficulty of localizing sounds underwater and thus identifying vocalizing individuals. Male bottlenose dolphins (Tursiops sp.; speckled form) in Shark Bay, Western Australia produce a vocalization we call 'pops'. Pops are narrow-band, low frequency pulses with peak energy between 300 and 3000 Hz and are typically produced in trains of 3-30 pops at rates of 6-12 pops/s. Observations on the pop vocalization and associated behavior were made as part of a long-term study of bottlenose dolphins in Shark Bay. During 1987-88 seven dolphins, including three males, frequented a shallow water area where they were daily provisioned with fish by tourists and fishermen. The three males often produced pops when accompanied by single female consorts into the shallows. Fortuitously, the males often remained at the surface where pops were audible in air, enabling us to identify the popping individual. All 12 of the female consorts in the study turned in towards males at a higher rate when the males were popping than when they were not popping. All 19 occurrences of one form of aggression, 'head-jerks', were associated with pops. We conclude that pops are a threat vocalization which induces the female to remain close to the popping male during consortships.