Description and Classification
Cetaceans - the taxonomic order including porpoises, dolphins and whales - are classified as mammals. They are well adapted to their marine environment with a streamlined, virtually hairless body and front limbs that have evolved into flippers, and internal skeletal evidence of the rear limbs that their terrestrial ancestors possessed. Despite these adaptations they remain true mammals, breathing air with lungs and giving birth to live young which suckle on nutritious milk produced by the mother's mammary glands. The right whale's milk is so rich that newborns can gain 900 kg in a little more than a month.
The order Cetacea is divided into two suborders: Odontoceti (toothed whales) and Mysticeti (baleen whales). Odontocetes comprise 90 percent of all cetaceans and are generally smaller than mysticetes. Odontocetes use their teeth to capture prey. Mysticetes feed using a filtering structure called baleen, a series of keratinous plates that hang from the upper jaw with a hair-like fringe on the inner edge. In the case of right whales, prey is strained from the water, trapped on the fringe, and then swallowed. Baleen whales are impressive in size, from 6.5 m in length for a pygmy right whale to 33 m in length for a blue whale. Right whales are classified as Mysticetes (baleen whales) and feed on zooplankton.
a) Teeth of an Orca. Odontocetes or toothed whales are characterized by the presence of teeth. b) Right whale skim feeding. Instead of teeth, Mysticetes or baleen whales have baleen plates hanging down from the upper jaw.
The taxonomic status (i.e. level of grouping by which organisms are classified within the animal kingdom) of the right whale genus was determined using genetic and morphological data. Three different species of right whales (genus Eubalaena) were defined in 2000 by the International Whaling Commission's Scientific Committee: North Atlantic right whales (E. glacialis), North Pacific right whales (E. japonica), and Southern right whales (E. australis). Warm equatorial waters and Arctic ice geographically separate the three species.
Distinguishing features of right whales: V-shaped blow, callosities, paddle-shaped flippers, and broad black tail. a) V-shaped blow seen from a distance. b) Right whale lifting its head vertically out of the water showing callosities covered with cyamids (whale lice). c) Right whale on its side with left, paddle-shaped flipper raised. d) Broad, smooth-edged, all-black tail (or flukes) that is raised into the air when the whale dives.
Adult North Atlantic right whales average 17 m in length, with adult females usually 1 m longer than adult males. Full size right whales weigh approximately 60-70 metric tonnes. Their bodies are black with the occasional white patch (pigmentation) on the belly or chin. In the field, they can be differentiated from other large whales by their lack of a dorsal fin, characteristic V-shaped blow and a broad tail (flukes) that is raised into the air when the whale dives. As there is a no reliable method to age right whales their maximum lifespan has not been determined, but sighting data have shown they can live at least 70 years 1.
Cyamids (whale lice), an amphipod that
can grow to about 1.5 cm, make the dark
callosities appear light yellow, cream, or
orange in colour from a distance.
Right whales have a distinctive callosity pattern that makes each individual unique. Callosities are thickened and hardened black or grey patches of skin found on the top of the head (rostrum), along the upper edge of the lower lip and jaw, behind blowholes, over the eyes, and on the chin, which is essentially the same places humans have hair on their heads. Callosities are covered with cyamids (whale lice), an amphipod that can grow to about 1.5 cm, which make the dark callosities appear light yellow, cream, or orange in colour. Researchers use these unique features to distinguish one right whale from another. An extensive photo-identification catalogue is archived at the New England Aquarium, Boston, Massachusetts 2 and contains more than 30,000 sighting records of 430+ individuals photographed from 1935 to the present.
1 Hamilton, P. K., A. R. Knowlton, M. K. Marx, and S. D. Kraus. 1998. Age structure and longevity in North Atlantic right whales (Eubalaena glacialis) and their relation to reproduction. Marine Ecology Progress Series 171:285-292.
2 Kraus, S. D., K. E. Moore, C. E. Price, M. J. Crone, W. A. Watkins, H. E. Winn, and J. H. Prescott. 1986. The use of photographs to identify individual North Atlantic right whales (Eubalaena glacialis). Pages 145-151 in R. L. Brownell, Jr., P. B. Best, and J. H. Prescott, eds. Right Whales: Past and Present Status. International Whaling Commission, Cambridge, UK.