Commerson's Dolphin
Encyclopedia
Commerson's Dolphin is one of four dolphin
s in the Cephalorhynchus genus. 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
.
, 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. Its appearance resembles that of a porpoise
, but its conspicuous behaviour (see behaviour below) 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 nine 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 second population (discovered in the 1950s) resides near the Kerguelen Islands, 8,000 km to the east of their nearest special cousins. 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:
The 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. They are also known to enjoy swimming 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 sub-population supplement their diet with crustacean
s.
in its Red List of Threatened Species. The proximity of the dolphin to the shore makes accidental killing in gillnet
s 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.
The Commerson's dolphin population of South America is listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
, Aquatica
in Florida, Zoo Duisburg in Germany (until 2004), and several aquariums in Japan.
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s in the Cephalorhynchus genus. 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
Strait of Magellan
The Strait of Magellan comprises a navigable sea route immediately south of mainland South America and north of Tierra del Fuego...
.
Physical description
Commerson's Dolphin has a very distinctive patterning. It has a black head, dorsal finDorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
, 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
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
, at 23 kg (51 lb) and 1.36 m (4.5 ft), may be the smallest adult cetacean on record. Its appearance resembles that of a porpoise
Porpoise
Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen...
, but its conspicuous behaviour (see behaviour below) 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
Kerguelen Islands
The Kerguelen Islands , also known as the Desolation Islands, are a group of islands in the southern Indian Ocean constituting the emerged part of the otherwise submerged Kerguelen Plateau. The islands, along with Adélie Land, the Crozet Islands and the Amsterdam and Saint Paul Islands are part of...
.
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 nine 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.
Population and distribution
The species is distributed in two locations. The larger population is found inshore in various inlets in Argentina, in the Strait of Magellan and near the Falkland IslandsFalkland Islands
The Falkland Islands are an archipelago in the South Atlantic Ocean, located about from the coast of mainland South America. The archipelago consists of East Falkland, West Falkland and 776 lesser islands. The capital, Stanley, is on East Falkland...
. The second population (discovered in the 1950s) resides near the Kerguelen Islands, 8,000 km to the east of their nearest special cousins. 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:
- the southern coast of South AmericaSouth AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
around Puerto DeseadoPuerto DeseadoPuerto Deseado, originally called Port Desire, is a city of about 15,000 inhabitants and a fishing port in Patagonia in Santa Cruz Province of Argentina, on the estuary of the Deseado River....
, Tierra del FuegoTierra del FuegoTierra del Fuego is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of a main island Isla Grande de Tierra del Fuego divided between Chile and Argentina with an area of , and a group of smaller islands including Cape...
and the Falkland IslandsFalkland IslandsThe Falkland Islands are an archipelago in the South Atlantic Ocean, located about from the coast of mainland South America. The archipelago consists of East Falkland, West Falkland and 776 lesser islands. The capital, Stanley, is on East Falkland...
, and - waters near the Kerguelen IslandsKerguelen IslandsThe Kerguelen Islands , also known as the Desolation Islands, are a group of islands in the southern Indian Ocean constituting the emerged part of the otherwise submerged Kerguelen Plateau. The islands, along with Adélie Land, the Crozet Islands and the Amsterdam and Saint Paul Islands are part of...
in the southern part of the Indian OceanIndian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
.
Behavior
This dolphin feeds on a mix of coastal and pelagic fish
Pelagic fish
Pelagic fish live near the surface or in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs.The marine pelagic...
and squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
. Those in the South American sub-population supplement their diet with crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s.
Conservation
The IUCN lists Commerson's Dolphin as Data DeficientData Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
in its Red List of Threatened Species. The proximity of the dolphin to the shore makes accidental killing in gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
s a common occurrence. The dolphin was killed for use as crab bait
Bait (luring substance)
Bait is any substance used to attract prey, e.g. in a mousetrap.-In Australia:Baiting in Australia refers to specific campaigns to control foxes, wild dogs and dingos by poisoning in areas where they are a problem...
by some Argentinian and Chilean fishermen in the 1970s and 1980s, but this practice has since been curtailed.
The Commerson's dolphin population of South America is listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
Captivity
About two dozen Commerson's Dolphins live in aquariums in the world, including SeaWorld San DiegoSeaWorld San Diego
SeaWorld San Diego is an animal theme park, oceanarium, and marine mammal park, located in San Diego, California, United States. The park is owned by SeaWorld Parks & Entertainment, a division of The Blackstone Group....
, Aquatica
Aquatica (Orlando)
Aquatica is a water park operated by SeaWorld Parks & Entertainment and located near Orlando, Florida. The park, which opened to guests on March 1, 2008, is a companion to SeaWorld Orlando and is located across International Drive from the main theme park...
in Florida, Zoo Duisburg in Germany (until 2004), and several aquariums in Japan.