Sound velocity in the head of the dwarf sperm whale, Kogia sima, with anatomical and functional discussion

Abstract

The velocity of sound through spermaceti oil from the melon of two Kogia sima specimens, stranded in Florida in 1995, was determined across a range of temperatures between 7 and 38°C and at pressures between 0 and 90 atm. Sound velocity values ranged between 1395-1669 m s−1, increasing linearly with increasing pressure but decreasing non-linearly with increasing temperature. Polynomials were generated to describe sound velocity as a function of temperature and pressure for the core and peripheral lipids of the melon. The results suggest that, at normal body temperature, sound travelling from the back to the front of the melon would have a tendency to focus during dives to any depth, largely due to heat exchange across the periphery of the melon. Effects of changes in ambient temperature and pressure are described and discussed in relation to anatomy.

Lipid class and depth-specific thermal properties in the blubber of two species of odontocete cetaceans, the short-finned pilot whale (Globicephala macrorhynchus) and the pygmy sperm whale (Kogia breviceps)

“…Thus, K. breviceps blubber provided significantly better insulation, ~1.5 times that of G. macrorhynchus blubber. Insulation is important to these animals because both species may experience as much as a 20°C drop in ambient temperatures over the course of a dive (Goold and Clarke, 2000). Globicephala macrorhynchus has been recorded to dive to a maximum depth of 1018m for 21min (Aguilar Soto et al, 2008).…”

Cuvier's beaked whale (Ziphius cavirostris) head tissues:physical properties and CT imaging

“…Studies of the chemical composition of melon acoustic lipids and mandibular fat bodies suggest complex chemical topography associated with acoustic functionality (Blomberg and Lindholm, 1976;Koopman et al, 2003;Litchfield et al, 1973;Varanasi et al, 1982). Sound speed in melon lipids has been shown to vary with chemical composition and topography in the melon (Blomberg and Jensen, 1976;Blomberg and Lindhom, 1976;Flewellen and Morris, 1978;Goold et al, 1996;Goold and Clarke, 2000;Litchfield et al, 1973Litchfield et al, , 1979Norris and Harvey, 1974;Varanasi et al, 1982). Sound speed in the tissues surrounding the melon has not been studied.…”

Temporal variation in dwarf sperm whale (Kogia sima) habitat use and group size off Great Abaco Island, the Bahamas

“…Predation risk (Lima andDill 1990), interspecific competition (e.g., Robertson 1996), and Although the threat of shark predation to dwarf sperm whales is often overlooked, parasites found in stranded individuals suggest that attacks may be mnore comnmon than generally appreciated (see Gibson et aL 1998, Walker 2001, Anzar 2007. Sharks are the final host for larval cestodes (Cheung 1993, Caira andHealy 2004), such as Phyllobothrium deiphini, that are commonly found encysted in dwarf sperm whale blubber (Nagorsen 1985, Cardonna-Maldonado and Mignucci-Giannoni 1999, Goold and Clarke 2000. In order for these parasites to be transmitted, shark predation and scavenging of dwarf sperm whale carcasses mnust be relatively frequent.…”