Chilean dolphin Temporal range: Holocene [1] | |
---|---|
Chilean dolphins around Isla Gordon | |
Size compared to an average human | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Infraorder: | Cetacea |
Family: | Delphinidae |
Genus: | Cephalorhynchus |
Species: | C. eutropia |
Binomial name | |
Cephalorhynchus eutropia Gray, 1846 | |
Chilean dolphin range |
The Chilean dolphin (Cephalorhynchus eutropia), also known as the Black dolphin, is one of four dolphins in the genus Cephalorhynchus . The dolphin is found only off the coast of Chile; it is commonly referred to in the country as tonina. [4]
The Chilean dolphin is small at around 1.7 metres (5 ft 7 in) in length, with a blunt head. These characteristics often make for its incorrect identification as a porpoise. This dolphin is thickly shaped with its girth up to two-thirds its length. The dorsal fin and flippers are small in proportion to body size in comparison with other dolphins. The throat, underside, and the closest part of the flippers to the body are white. The remainder of the body is a mix of greys. It has 28–34 pairs of teeth in the upper jaw and 29–33 in the lower.
The Chilean dolphin is normally sighted in small groups of around two to ten individuals, with some larger gatherings occasionally sighted.
Longevity, gestation, and lactation periods are not known, but are believed to be similar in length to the more studied, and similar, Hector's and Commerson's dolphins which have a gestation period of about 10 months to one year and maximum longevity of 20 years.
The population of the Chilean dolphin, perhaps one of the least studied of all cetaceans, is not known with certainty. There may be as many as a few thousand individuals, although at least one researcher, Steve Leatherwood, has suggested the population may be much lower (see also for a survey of South American cetacean population with data on the Chilean dolphin). Whatever its number, the Chilean dolphin is endemic to the coast of Chile and thought not to migrate. The dolphin is seen over a wider interval of latitudes than other Cephalorhynchus species — from Valparaíso at 33°S to Cape Horn at 55°S. The species prefers shallow water regions and more specifically areas near rivers and high tides. The close association with riverine and estuarine ecosystems makes Chilean dolphins extremely vulnerable to habitat loss both from coastal and upstream river basin degradation. The limited distribution and relatively inflexible habits of cultural degradation makes them particularly vulnerable to fragmentation and population loss in the face of increasing human activities in the far flung regions of the world.
Little is known about the reproduction of the Chilean dolphin. They mate in the early winter and females give birth to their offspring in the spring. Female dolphins usually have one calf every two years. Calves reach full maturity between ages 5 and 9 years [5]
The Chilean dolphin is listed on Appendix II [6] Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [6] as it has an unfavourable conservation status or would benefit significantly from international co-operation organized by tailored agreements. [7]
In the early part of the 20th century, the Chilean dolphin was commonly known as the black dolphin. This was later agreed to be a poor choice of name. Most of the few individual specimens studied by scientists were either washed-up individuals whose skin had darkened due to exposure to air or live specimens seen at sea but only at a distance (and so appeared darker than they were). As more specimens were studied, it became clear that the back of the dolphin was in fact a mixture of grey colours and that its underside was white. The scientific community is now universally agreed in naming the dolphin Chilean on account of its distribution along the coast of the country.
The La Plata dolphin, franciscana or toninha is a species of river dolphin found in coastal Atlantic waters of southeastern South America. It is a member of the Inioidea group and the only one that lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems. Commercialized areas that create agricultural runoffs and industrialized zones can affect the health of the La Plata dolphin, especially in regards to their contributions of waste and pollution, which can lead to habitat degradation and poisoned food among other concerns.
Risso's dolphin is a marine mammal and dolphin, the only species of the genus Grampus. Some of the most closely related species to these dolphins include: pilot whales, pygmy killer whales, melon-headed whales, and false killer whales. These dolphins grow to be about 10 ft in length and can be identified by heavy scarring that appears white. They are located worldwide in cold to temperate waters, but most typically found along continental shelves due to their eating habits. Risso's dolphins have a diet that contains primarily cephalopods. They are able to search for prey at various depths due to their ability to reach depths of almost 600m. Individuals typically travel in pods ranging anywhere from 10 to 50 dolphins, with which they form tight social bonds.
The white-beaked dolphin is a marine mammal belonging to the family Delphinidae in the suborder Odontoceti.
The pygmy right whale is a species of baleen whale. It may be a member of the cetotheres, a family of baleen whales which until 2012 were thought to be extinct; C. marginata has otherwise been considered the sole member of the family Neobalaenidae and is the only member of the genus Caperea. First described by John Edward Gray in 1846, it is the smallest of the baleen whales, ranging between 6 and 6.5 metres in length and 3,000 and 3,500 kilograms in mass. Despite its name, the pygmy right whale may have more in common with the gray whale and rorquals than the bowhead and right whales.
The Indo-Pacific finless porpoise is one of eight porpoise species. The species ranges throughout most of the Indian Ocean, as well as the tropical and subtropical Pacific from Indonesia north to the Taiwan Strait. Overlapping with this species in the Taiwan Strait and replacing it northwards is the East Asian finless porpoise.
The Irrawaddy dolphin is a euryhaline species of oceanic dolphin found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. It closely resembles the Australian snubfin dolphin, which was not described as a separate species until 2005. It has a slate blue to a slate gray color. Although found in much of the riverine and marine zones of South and Southeast Asia, the only concentrated lagoon populations are found in Chilika Lake in Odisha, India and Songkhla Lake in southern Thailand.
Burmeister's porpoise is a species of porpoise endemic to the coast of South America. It was first described by Hermann Burmeister, for whom the species is named, in 1865.
Commerson's dolphin, also referred to by the common names jacobita, skunk dolphin, piebald dolphin, panda dolphin, or tonina overa, is a small oceanic dolphin of the genus Cephalorhynchus. Commerson's dolphin has two geographically-isolated but locally-common subspecies. The principal subspecies, C.c.commersonii, has sharply-delineated black-and-white patterning and is found around the tip of South America. The secondary subspecies, C.c.kerguelenensis, is larger than C.c.commersonii, has a less-sharply delineated dark and light grey patterning with a white ventral band, and is found around the Kerguelen Islands in the Indian Ocean.
Heaviside's dolphin is one of four dolphins in the genus Cephalorhynchus. The small cetacean is endemic to the Benguela ecosystem along the southwest coast of Africa.
Humpback dolphins are members of the genus Sousa. These dolphins are characterized by the conspicuous humps and elongated dorsal fins found on the backs of adults of the species. Humpback dolphins inhabit shallow nearshore waters along coastlines across Australia, Africa, and Asia. Their preference for these habitats exposes them to various human activities such as fisheries entanglement, boat traffic, pollution, and habitat loss. Despite these risks, their nearshore presence facilitates easy observation from land.
Fraser's dolphin or the Sarawak dolphin is a cetacean in the family Delphinidae found in deep waters in the Pacific Ocean and to a lesser extent in the Indian and Atlantic Oceans.
The hourglass dolphin is a small dolphin in the family Delphinidae that inhabits offshore Antarctic and sub-Antarctic waters. It is commonly seen from ships crossing the Drake Passage but has a circumpolar distribution.
Peale's dolphin is a small dolphin found in the waters around Tierra del Fuego at the foot of South America. It is also commonly known as the black-chinned dolphin or even Peale's black-chinned dolphin. However, since Rice's work Peale's dolphin has been adopted as the standard common name.
The pantropical spotted dolphin is a species of dolphin found in all the world's temperate and tropical oceans. The species was beginning to come under threat due to the killing of millions of individuals in tuna purse seines. In the 1980s, the rise of "dolphin-friendly" tuna capture methods saved millions of the species in the eastern Pacific Ocean and it is now one of the most abundant dolphin species in the world.
The spinner dolphin is a small dolphin found in off-shore tropical waters around the world. It is famous for its acrobatic displays in which it rotates around its longitudinal axis as it leaps through the air. It is a member of the family Delphinidae of toothed whales.
The Clymene dolphin, in older texts known as the short-snouted spinner dolphin, is a dolphin endemic to the Atlantic Ocean. It is the only confirmed case of hybrid speciation in marine mammals, descending from the spinner dolphin and the striped dolphin.
The striped dolphin is a dolphin found in temperate and tropical waters of all the world's oceans. It is a member of the oceanic dolphin family, Delphinidae.
The dwarf sperm whale is a sperm whale that inhabits temperate and tropical oceans worldwide, in particular continental shelves and slopes. It was first described by biologist Richard Owen in 1866, based on illustrations by naturalist Sir Walter Elliot. The species was considered to be synonymous with the pygmy sperm whale from 1878 until 1998. The dwarf sperm whale is a small whale, 2 to 2.7 m and 136 to 272 kg, that has a grey coloration, square head, small jaw, and robust body. Its appearance is very similar to the pygmy sperm whale, distinguished mainly by the position of the dorsal fin on the body–nearer the middle in the dwarf sperm whale and nearer the tail in the other.
The Australian snubfin dolphin is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin and was not described as a separate species until 2005. The closest relative to the genus Orcaella is the killer whale, Orcinus orca. The Australian snubfin has three colors on its skin, while the Irrawaddy dolphin only has two. The skull and the fins also show minor differences between the two species.
The Convention on the Conservation of Migratory Species of Wild Animals, also known as the Convention on Migratory Species (CMS) or the Bonn Convention, is an international agreement that aims to conserve migratory species throughout their ranges. The agreement was signed under the auspices of the United Nations Environment Programme and is concerned with conservation of wildlife and habitats on a global scale.
Ribeiro, S., Viddi, F. A., Cordeiro, J. K., & Freitas, T. R. O. (2007). Fine-scale habitat selection of Chilean dolphins (cephalorhynchus eutropia): Interactions with aquaculture activities in southern chiloe island, chile. Journal of the Marine Biological Association of the United Kingdom, 87(1), 119–128. doi:10.1017/S0025315407051594