Physeteridaesperm whales

Last updated:

Three species in 2 genera ( Physeter, the giant sperm whale; and Kogia, containing two species called pygmy and dwarf sperm whales) make up this family. Sperm whales are found in all oceans except the Arctic. These whales include the very large giant sperm whale, which reaches lengths of over 18 m and weights in excess of 53,000 kg, and the (relatively!) dimunitive pygmy sperm whale, which attains a mere 4 m in length and 320 kg in weight.

Physeter has an enormous head, equalling 35% of the length of the body, with a greatly-developed facial depression that contains the spermaceti organ. This structure is derived from the melon of other odontocetes, and like the melon, may serve as a sort of acoustic lens. The mouth of Physeter is considerably undershot but the lower jaw is long. The dorsal fin is is low, thick, and rounded, and the flippers are broad and rounded. Physeter also has a dorsal ridge and thick ventral keel on the tail.

The species of Kogia, in contrast, have a much smaller head; they also have spermaceti organs, but these are too small to be of commercial interest. The lower jaw is short and the jaw is undershot. The dorsal fin is low and sickle-shaped, and the flippers narrow.

The throat region of both species has numerous shallow, irregular grooves.

The facial depression of physeterids extends to the sides of the skull and roofs over the temporal fossa, hiding the zygomatic arches from dorsal view. At the rear, it terminates in a high, semicircular occipital crest. The rostrum is broad, flat, and triangular. The blowhole is asymmetrical, S-shaped, and located on the left side of the snout. The lower jaw is very long and narrow, but as noted above, does not reach the end of the rostrum. The mandibular symphysis is more than 33% the length of the rami. The number of teeth ranges from 1/8 to 0/16 in Kogia and 0/25 in Physeter.

Physeter dives to amazing depths (over 1000 m) in pursuit of its primary prey, squid. It also takes sharks, skates, and fish. Dives may last for 80 minutes or more. Females and young males form schools of 20-40 individuals. These are joined by bull males during the breeding season. Larger aggregations are occasionally seen. Young males form loose bachelor herds, but become increasingly solitary as they age. Giant sperm whales are migratory, following the summer from northern to southern hemispheres. The habits of Kogia are less well known. These whales feed primarily but not exclusively on squid, with one species foraging in deep oceanic waters and the other over the continental shelf. Kogia appear to be solitary or to live in small pods.

Giant sperm whales were extremely important to the whaling industry. Sperm oil, extracted from the spermaceti organ and from the blubber, remains liquid even at low temperatures and was used as a fine industrial lubricant. Spermaceti, which when cooled solidifies into a waxy substance, was used for making candles and ointments. Sperm whales also produce ambergris, probably from waste coalescing around indigestible substances in the intestinal tract. Ambergris is used as a fixative in the manufacture of perfume. Sperm whales are now fully protected by international law.

Curiously, while sperm whales unquestionably have teeth, recent molecular data and a reanalysis of their anatomy has suggested that they may be highly derived mysticetes.

References and literature cited:

Nowak, R.M. and J.L. Paradiso. 1983. Walker's Mammals of the World, 4th edition . John Hopkins University Press, Baltimore, MD.

Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution: An Illustrated Guide. Facts on File Publications, UK. 251 pp.

Rice, D. W. 1984. Cetaceans. Pp. 447-490 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, N.Y. vii+576 pp.

Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.

Contributors

Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate