Right whale dolphin
The right whale dolphins, the Northern Right Whale Dolphin (Lissodelphis borealis) and the Southern Right Whale Dolphin (Lissodelphis peroni), are two of the easiest cetaceans to be identify at sea. Both these oceanic dolphins are colored black and white and have no dorsal fin. Despite scientists being long acquainted with these dolphins surprisingly little is known about them in terms of life history and behavior.
Both species have slender bodies, small, pointed flippers and a small fluke. Conspicuously neither species have a dorsal fin. The Northern Right Whale Dolphin is the only dolphin in the Pacific with this property. Similarly the Southern is the only finless dolphin in the southern hemisphere. The two species – apart from the geographical dislocation – can be readily distinguished by the extent of the whiteness on the body. Both have white bellies. However the Southern species has more extensive white – including the flanks, flippers, beak and forehead.
Both sexes become mature at about 10 years. Newborn Right Whale Dolphins are about half the length of their parents. The Southern species are typically 8 ft (250cm) in length 220 pounds (100kg) compared with the Northern dolphins maximum weight of 190 pounds (80kg). The dolphins live for about 40 years.
The Northern Right Whale Dolphin is widely distributed in the North Pacific in a band running from Kamchatka and mainland Japan in the west to British Columbia down to the Baja California peninsula in the east. It is not known with certainty if they follow a migratory pattern. However individuals have been observed close to the Californian shore following their main food source, squid, in winter and spring. Such sightings have not been recorded in summer. Otherwise these dolphins are pelagic. No global population estimates exist. There are an estimated 14,000 individuals close to the North American shoreline.
The Southern Right Whale Dolphin has a circumpolar distribution running from about 40Â° to 55Â°. They are sighted in the Tasman Sea in particular.
Both species are highly sociable. They move in groups of several hundred individuals and sometimes congregate in groups of 3000. The groups may also contain Dusky Dolphins and Pilot Whales (in the south) and Pacific White-sided Dolphins (in the north). These dolphins are some of the fastest swimmers. They can by turns become very boisterous and breach and tail-slap or become very quiet and almost undetectable at sea. The species will generally avoid boats, but bow riding has been recorded on occasion.
Right whale dolphiona are not hunted and therefore long-term survival of the species is currently assessed to be secure under present conditions. However tens of thousands of the northern species were killed in the 1980s due to them becoming caught in oceanic drift gillnets introduced at that time. Gillnets were banned by the United Nations in 1993. Conservation campaigners work vigorously to try to ensure these bans are retained.