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Commerson's dolphin (Cephalorhynchus commersonii) is one of four dolphins in the genus Cephalorhynchus. The species has also the common names skunk dolphin, piebald dolphin and panda dolphin. The dolphin is named for Philibert Commerson, who first described them in 1767 after he sighted them in the Strait of Magellan.[3]
Commerson's dolphin has a very distinctive patterning. It has a black head, dorsal fin, and fluke, with a white throat and body. The demarcation between the two colours is very clear-cut. This stocky creature is one of the smallest of all cetaceans growing to around 1.5 m (5 ft). A mature female caught off of south Patagonia, at 23 kg (51 lb) and 1.36 m (4.5 ft), may be the smallest adult cetacean on record.[4] Its appearance resembles that of a porpoise, but its conspicuous behaviour is typical of a dolphin. The dorsal fin has a long, straight leading edge which ends in a curved tip. The trailing is typically concave but not falcate. The fluke has a notch in the middle. This dolphin has no rostrum. It is not known why their distribution is limited to the southern coast of South America and the Kerguelen Islands.
Sexes are easily distinguished by the different shape of the black blotch on the belly — it is shaped like a teardrop in males but is more rounded in females. Females reach breeding age at six to 9 years. Males reach sexual maturity at about the same age. Mating occurs in the spring and summer and calving occurs after a gestation period of 11 months. The oldest known Commerson's dolphin died at age 18.
The two disjunct subspecies are separated by 130° of longitude and about 8,500 km (5,300 mi). The larger population (C.c.commersonii) is found inshore in various inlets in Argentina, in the Strait of Magellan and near the Falkland Islands. The second subspecies (C.c.kerguelenensis, discovered in the 1950s) resides near the Kerguelen Islands. They prefer shallow waters. Global populations are unknown, but the species is accepted to be locally common. A survey in 1984 estimated there to be 3,400 individuals in the Strait of Magellan.
The dolphin is found in two geographically disparate areas:
A vagrant individual was sighted on the Agulhas Bank off South Africa in 2004. This specimen was isolated from the Kerguelen population by 4,200 km (2,600 mi) and from the South American by 6,300 km (3,900 mi). However, the Antarctic Circumpolar Current would force an individual from the Kerguelen population to swim against the West Wind Drift.[5]
Commerson's dolphin is very active. It is often seen swimming rapidly on the surface and leaping from the water. It also spins and twists as it swims and may surf on breaking waves when very close to the shore. It will bow-ride and swim behind fast-moving boats. It is also known to swim upside-down, which is thought to improve the visibility of its prey.
This dolphin feeds on a mix of coastal and pelagic fish and squid. Those in the South American subpopulation supplement their diets with crustaceans.
The IUCN lists Commerson's dolphin as Data Deficient in its Red List of Threatened Species. The proximity of the dolphin to the shore makes accidental killing in gillnets a common occurrence. The dolphin was killed for use as crab bait by some Argentinian and Chilean fishermen in the 1970s and 1980s, but this practice has since been curtailed.[2]
The Commerson's dolphin population of South America is listed on Appendix II[6] of the
[1]
A few are accidentally killed in gill nets set for crabs along the Argentine coast, and local fishermen may kill them for food. Several have been shipped abroad to aquariums. Commerson's dolphins also inhabit waters heavy with human activity, creating a large danger for them.11
About two dozen Commerson's dolphins live in aquariums around the world, including SeaWorld San Diego, Aquatica in Florida, Duisburg Zoo in Germany (until 2004), and several aquariums in Japan.
[7]
Cnidaria, Sponge, Bacteria, Fungus, Biological classification
Animal, Gray whale, Humpback whale, Whale, Fish
French Southern and Antarctic Lands, Adélie Land, Crozet Islands, Madagascar, India
Argentina, United Kingdom, British Overseas Territories, Chile, Uruguay
Commerson's dolphin, Animal, Cetacea, Species, Taxonomy (biology)
Faroe Islands, Cetacea, Greek mythology, Japan, Killer whale
Greek mythology, Cetacea, Faroe Islands, Killer whale, False killer whale
Argentina, Philippines, Gillnet, Canada, Fisheries