Eschrichtiidaegray whale
This family contains a single living species, the gray whale. These whales are restricted today to the north Pacific (along east and west coasts); Atlantic populations are extinct.
Gray whales are large whales, ranging to over 14 m in length and over 30,000 kg in weight. They have a slender body with a low dorsal hump and no dorsal fin. The flippers are broad, and the tail has a folded ridge on its dorsal surface. The throat has two or three short grooves, unlike the multiple grooves of rorquals.
The skulls of gray whales differ from those of rorquals in that the telescoping of the bones that make up the dorsal surface is not as extreme. The nasals and nasal processes of the premaxillae extend posteriorly beyond the anterior border of the supraorbital processes of the frontals; the maxillae possess nasal processes; the nasals are large; the frontals are broadly exposed on the dorsal surface of the skull; the supraoccipital does not extend anteriorly beyond the zygomatic processes of the squamosal; and the rostrum is narrow and arched. The baleen plates are short and narrow.
Gray whales feed by swimming on their sides along the bottom, gulping mud by expanding their oral cavities rapidly (creating a strong inflow), and straining it through their fringed baleen plates. A wide variety of invertebrates is taken, but crustaceans are the main source of nutrition for this species.
Like rorquals, gray whales are migratory species. They summer at high latitudes in the Pacific, migrating during autumn to the west coast of Baja California and the south coast of Korea. Pregnant females gather in shallow lagoons to give birth to calves. Gray whales travel singly or in small groups of up to a dozen or so individuals.
Populations of this species were nearly driven to extinction in the early part of this century. Protected from whaling, the eastern Pacific population has made a strong comeback.
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.
Species included in database:
Contributors
Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.
Glossary
- bilateral symmetry
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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
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uses smells or other chemicals to communicate
- endothermic
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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
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having the capacity to move from one place to another.
- sexual
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reproduction that includes combining the genetic contribution of two individuals, a male and a female
- tactile
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uses touch to communicate