Northern right whale dolphin
Northern right whale dolphin pair. Source: National Marine Fisheries Service/NOAA
The Northern right whale dolphin is a marine mammal within the porpoise family of the Cetaceans. This species is best known for being the only dolphin in the north Pacific Ocean lacking a dorsal fin. Often mistaken for a sea lion or fur seal, this dolphin is most often found in large herds ranging from 100 to 200 individuals, however, they have occasionally been found in groups as large as 3000 members. It is also known as the Pacific rightwhale porpoise, snake porpoise, northern right whale dolphin, northern right-whale dolphin, Pacific rightwhale porpoise, and Right whale dolphin
The Northern right whale dolphins are a sister species to the Southern right-whale dolphin. The differences between the two species are their sizes, geographic location and coloration. The Northern right whale dolphins prefer the northern hemisphere because of its warmer water temperatures; moreover the Northern right whale dolphin exhibits less striking coloration patterns, and are smaller in size.
 Size comparison of typical northern right-whale dolphin to an average-sized human adult. Source: Chris Huh
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Scientific Classification Kingdom: Animalia (Animals) |
Contents
Physical description
Northern right whale dolphins have an unusually slender body shape, and they do not have a dorsal fin or ridge. They have small, curved flippers, and small flukes. They are mostly black, but they have a well defined white band on their belly. Males and females have the same body shape and color pattern, the only sexually dimorphism being that males can attain greater length (up to three meters) and body mass than females.
Reproduction
Very little is known about reproduction or mating in this species.
Behavior
Northern right whale dolphins usually travel in large groups of up to 2000 individuals, with the average herd size being about 200 members. Groups sometimes swim in various geometric configurations, such as a V-shape formation. This dolphin species can swim swiftly, attaining speeds of over 40 kilometres per hour. They can swim near the surface without appreciably disturbing the water surface, probably because they do not have a dorsal fin. They are known to occasionally perform fluke slaps and breaches. The maximum dive time that has been recorded is 6.25 minutes. They often travel with other species ofmarine mammals, most commonly the Pacific white-sided dolphin. Click and whistle vocalizations have been reported in Northern right whale dolphins, but these have not been studiedcatalogued in exhaustive detail.
Distribution
These cetaceans are found only in the northern Pacific Ocean, between the latitudes 35 degrees North and 51 degrees North.
Habitat
These animals live in deep continental shelf and offshore waters, where the temperatures vary between eight and 24 degrees C. They approach shore only where very deep water can be found near the coast.
Ecosystem roles
The northern right whale dolphin is often seen in association with the Pacific white-sided dolphin and the Short-finned pilot whale.
Feeding habits
Northern right whale dolphins feed chiefly on squid and lanternfish, but may also consume other prey species.
Conservation status
The North Pacific squid driftnet fishery operated out of Japan, Korea, and Taiwan targets Northern right whale dolphins. It is estimated that between 1985 and 1990 this fishery took 15,000 to 20,000 dolphins per year. The Northern right whale dophin population has been depleted to anywhere from 24 to 73 percent of its pre-exploitation size. A moratorium on high seas driftnets could allow population levels to increase to previous levels.
IUCN Red list classified the Northern right whale dolphin as a species of Least Concern, which finding may be questionable in light of the intense exploitation of the prior several decades.
Threats
Some whalers harvest this species in order to use blubber from these animals to produce oil.
References and Further reading
- IUCN Red List. Lissodelphis borealis
- NOAA, Northern Right Whale Dolphin (Lissodelphis borealis)
- Encyclopedia of Life. 2010. Lissodelphis borealis (Peale, 1848) Northern right-whale dolphin
- Banks, R. C., R. W. McDiarmid, A. L. Gardner, and W. C. Starnes. 2003. Checklist of Vertebrates of the United States, the U.S. Territories, and Canada
- Banks, R. C., R. W. McDiarmid, and A. L. Gardner. 1987. Checklist of Vertebrates of the United States, the U.S. Territories, and Canada. Resource Publication, no. 166. 79
- Don Wilson and Sue Ruff (1999) The Smithsonian Book of North American Mammals. Smithsonian Books: Washington.
- Foster, L. 1948. The World's Whales. London: Hart-Davis and MacGibbon.
- Gill, 1865. Proceedings of the Academy of Natural Sciences of Philadelphia, 17:177.
- IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
- Leatherwood, S., R. Reeves. 1983. Whales and Dolphins. San Francisco: Sierra Club Books.
- Mead, James G., and Robert L. Brownell, Jr. / Wilson, Don E., and DeeAnn M. Reeder, eds. 2005. Order Cetacea. Mammal Species of the World: A Taxonomic and Geographic Reference, 3rd ed., vol. 1. 723-743
- Perrin, W. (2010). Lagenorhynchus obliquidens Gill, 1865. In: Perrin, W.F. World Cetacea Database. Accessed through: Perrin, W.F. World Cetacea Database
- Rice, Dale W. 1998. Marine Mammals of the World: Systematics and Distribution. Special Publications of the Society for Marine Mammals, no. 4. ix + 231
- Richard Weigl (2005) Longevity of Mammals in Captivity; from the Living Collections of the World. Kleine Senckenberg-Reihe 48: Stuttgart.
- UNESCO-IOC Register of Marine Organisms
- Watson, L. 1981. Sea Guide to Whales of the World. London: Hutchinson.
- Wilson, Don E., and DeeAnn M. Reeder, eds. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference, 2nd ed., 3rd printing. xviii + 1207
- Wilson, Don E., and F. Russell Cole. 2000. Common Names of Mammals of the World. xiv + 204
- Wilson, Don E., and Sue Ruff, eds. 1999. The Smithsonian Book of North American Mammals. xxv + 750
