Sperm Whales: Physiology of the Deep Diver

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Introduction The Order Cetacea is one of the most distinctive and highly specialized groups of mammals. Over the course of evolutionary history, cetaceans have become adapted to surviving and prospering in a vast aquatic environment. One of the most important obstacles they have overcome is the ability to be obligate ocean dwellers while still breathing oxygen. Cetaceans are able to remain underwater for extended periods of time, returning only to the surface to exhale. Diving beneath the surface is an essential component of life for these species since almost all of their food sources are found under the surface of the ocean. One of the most-well known diving cetaceans is the sperm whale (Physeter macrocephalus). The world’s largest carnivore, this massive cetacean makes extremely deep dives for food, mainly squid and octopus, but also fish and sometimes giant squid (Burnie and Wilson 2005). Sperm whales can dive to depths of 400 to 1200 meters, and for durations of up to 138 minutes (Watwood et al. 2006). The majority of sperm whale dives have been reported to last from 33 to 53 minutes (2006). Sperm whales have to overcome several fundamental problems while diving at such great depths: the effects of pressure and the need to actively forage while holding their breath. Adaptations to pressure have to deal with the mechanical effects of pressure and the increased solubility of gas at depth (Costa 2007). Adaptations to breath-holding diving center around modifications in metabolism, blood flow, and an increased oxygen storage capacity (2007). Effects of Pressure As sperm whales dive, they must deal with the direct effect of pressure that is associated with the volume change of air-filled spaces in their bodies. Changes in air v... ... middle of paper ... ...W, Rotstein DS, Rowles TK, Simmons SE, Van Bonn W, Weathersby PK, Weise MJ, Williams TM, Tyack PL (2011) Deadly diving? Physiological and behavioral management of decompression stress in diving mammals. Proceedings of the Royal Society of Biological Sciences. 279:1041-1050 Kooyman GL (1973) Respiratory adaptations of marine mammals. American Zoologist. 13(2):457-468 Miller PJO, Johnson MP, Tyack PL, Terray EA (2004) Swimming gaits, passive drag and buoyancy of diving sperm whales Physeter macrocephalus. The Journal of Experimental Biology. 207:1953-1967 Watkins WA, Daher MA, Fristrup KM, Howald TJ (1993) Sperm whales tagged with transponders and tracked underwater by sonar. Marine Mammal Society. 9(1):55-67 Watwood SL, Miller PJO, Johnson M, Madsen PT, Tyack PL (2006) Foraging behavior of sperm whales (Physeter macrocephalus). Journal of Animal Ecology 75(3):814-825

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