Taxonomy & Nomenclature
Physical Description / Field Identification
The northern right whale dolphin and its Southern Hemisphere relative are the slenderest of all small cetaceans. At close range, northern right whale dolphins are unmistakable; they are the only small cetaceans in their range with no dorsal fin. The flukes and flippers are small, and the beak is short, but well-defined.
Northern right whale dolphins are primarily black, with a white band from the throat to the fluke notch that widens to cover the entire area between the flippers, and a white spot just behind the tip of the lower jaw. The trailing edges of the flukes have light gray edging above and white below. Young animals have muted color patterns of dark gray and light gray.
The mouth contains 37-54 pairs of sharp slender teeth in each jaw. Measured adults have been up to 2.3 m (females) and 3.1 m (males). Length at birth is unknown, but is thought to be somewhat less than 1 m. Maximum known weight is 115 kg.
Can be Confused With
The slender finless body will allow easy separation from other North Pacific small cetaceans. However, porpoising California sea lions may cause confusion at a distance.
Distribution
The northern right whale dolphin is an oceanic species, inhabiting cool and warm temperate regions of the North Pacific only between about 30°N and 50°N. It forms an antitropical species pair with the southern right whale dolphin.
Ecology and Behavior
Most herds number between 100 and 200 individuals, but groups of up to 3,000 have been seen. Groups mixed with other marine mammals, especially Pacific-white-sided dolphins (with which they share a nearly identical range), are not uncommon. Northern right whale dolphins are fast swimmers, sometimes creating a great surface disturbance with their low-angle leaps and belly flops. They bowride, especially when accompanied by other species of dolphins.
There appears to be a calving peak in winter to early spring.
Feeding and Prey
Although market squid and lanternfish are the major prey items for right whale dolphins off southern California, a variety of surface and midwater species are taken by this species.
Threats and Status
Northern right whale dolphins have never been hunted extensively, although they are sometimes taken in Japan’s small cetacean fisheries. Incidental catches have occurred in Japanese and Russian purse seines, Japanese salmon driftnets, and Anerican shark and swordfish drifnets. However, the largest takes in recent years were in the North Pacific squid driftnet fisheries, which took many thousands annually, until they were shut-down by international law in the 1990s. Currently, they are ‘Not Listed’ (IUCN) and ‘Not Listed’ (ESA).
Links
References
Baird, R.W. and P.J. Stacey. 1991. Status of the northern right whale dolphin, Lissodelphis borealis, in Canada. Canadian Field-Naturalist 105:243-250.
Dizon, A.E., C.A. Leduc and R.G. Leduc. 1994. Intraspecific structure of the northern right whale dolphin (Lissodelphis borealis) the power of an analysis of molecular variation for differentiating genetic stocks. CALCOFI Reports 35:61-67.
Ferrero, R.C. and W.A. Walker. 1993. Growth and reproduction of the northern right whale dolphin, Lissodelphis borealis, in the offshore waters of the North Pacific Ocean. Canadian Journal of Zoology 71:2335-2344.
Jefferson, T.A. and M.W. Newcomer. 1993. Lissodelphis borealis. Mammalian Species 425:1-6.
Jefferson, T.A., M.W. Newcomer, S. Leatherwood and K. Van Waerebeek. 1994. Right whale dolphins Lissodelphis borealis (Peale, 1848) and Lissodelphis peronii (Lacepede, 1804). pp. 335-362 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Volume 5: The first book of dolphins. Academic Press.
Lipsky, J.D. 2002. Right whale dolphins Lissodelphis borealis and L. peronii. pp. 1030-1033 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
