Fraser's Dolphin
Encyclopedia
Fraser's Dolphin or 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 Ocean
s.
, Borneo
. He donated it to the British Museum
. The skull remained unstudied until 1956 when Francis Fraser
examined it and concluded that it was similar to species in both the Lagenorhynchus
and Delphinus
genera but not the same as either. A new genus was created by simply merging these two names together. The specific name is given in Hose's honour.
It wasn't until 1971 that the whole body of a Fraser's Dolphin, as it was by then becoming known, was discovered. At that time washed-up specimens were found on Cocos Island
in the eastern Pacific, in South Australia
and in South Africa
.
and beak are also insubstantial. The upper side is a gray-blue to gray-brown. A dirty cream colored line runs along the flanks from the beak, above the eye, to the anus. There is a dark stripe under this line. The belly and throat are usually white, sometimes tinged pink. The lack of a prominent beak is a distinguishing characteristic of the dolphin. From a distance however it may be confused with the Striped Dolphin
which has a similar coloration and is found in the same regions.
Fraser's dolphins swim quickly in large tightly packed groups of about 100 to 1000 in number. Often porpoising, the group chop up the water tremendously. The sight of seeing a large group fleeing from a fishing vessels has been reported as "very dramatic".
It is also marked by having the smallest genitalia of any open sea dolphin.
The species feeds on pelagic fish
, squid
and shrimp
found some distance below the surface of the water (200 metres (656.2 ft) to 500 metres (1,640.4 ft)). Virtually no sunlight penetrates this depth, so feeding is carried out using echolocation
alone.
The Dolphin is normally sighted in deep tropical waters; between 30° S and 20° N. The Eastern Pacific is the most reliable site for viewings. Groups of stranded dolphins have been found as far afield as France
and Uruguay
. However these are regarded as anomalous and possibly due to unusual oceanographic
conditions, such as El Niño.
The species is also relatively common in the Gulf of Mexico
but less so in the rest of the Atlantic Ocean.
), since they have an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
In addition, Fraser's dolphin is covered by Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU).
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
and to a lesser extent in the Indian
Indian Ocean
The 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...
and Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
s.
Taxonomy
In 1895, Charles E. Hose found a skull on a beach in SarawakSarawak
Sarawak is one of two Malaysian states on the island of Borneo. Known as Bumi Kenyalang , Sarawak is situated on the north-west of the island. It is the largest state in Malaysia followed by Sabah, the second largest state located to the North- East.The administrative capital is Kuching, which...
, Borneo
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
. He donated it to the British Museum
British Museum
The British Museum is a museum of human history and culture in London. Its collections, which number more than seven million objects, are amongst the largest and most comprehensive in the world and originate from all continents, illustrating and documenting the story of human culture from its...
. The skull remained unstudied until 1956 when Francis Fraser
Francis Charles Fraser
Francis Charles Fraser, born 16 June 1903 died 21 October 1978, was one of the world's leading authorities on cetacea . He worked at the British Museum of Natural History from 1933 to 1969. He was elected a Fellow of the Royal Society in 1966.Fraser's dolphin is named in his honour....
examined it and concluded that it was similar to species in both the Lagenorhynchus
Lagenorhynchus
Lagenorhynchus is a genus in the order Cetacea, traditionally containing six species:* white-beaked dolphin, Lagenorhynchus albirostris* Atlantic white-sided dolphin, Lagenorhynchus acutus...
and Delphinus
Delphinus
Delphinus is a constellation in the northern sky, close to the celestial equator. Its name is Latin for dolphin. Delphinus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains among the 88 modern constellations recognized by the International Astronomical...
genera but not the same as either. A new genus was created by simply merging these two names together. The specific name is given in Hose's honour.
It wasn't until 1971 that the whole body of a Fraser's Dolphin, as it was by then becoming known, was discovered. At that time washed-up specimens were found on Cocos Island
Cocos Island
Cocos Island is an uninhabited island located off the shore of Costa Rica . It constitutes the 11th district of Puntarenas Canton of the province of Puntarenas. It is one of the National Parks of Costa Rica...
in the eastern Pacific, in South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
and in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
.
Description
Fraser's dolphins are about 1 metres (3.3 ft) long and 20 kg weight at birth, growing to 2.75 metres (9 ft) and 200 kg at adulthood. They have a stocky build, a small fin in relation to the size of the body, conspicuously small flippers. The 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 beak are also insubstantial. The upper side is a gray-blue to gray-brown. A dirty cream colored line runs along the flanks from the beak, above the eye, to the anus. There is a dark stripe under this line. The belly and throat are usually white, sometimes tinged pink. The lack of a prominent beak is a distinguishing characteristic of the dolphin. From a distance however it may be confused with the Striped Dolphin
Striped Dolphin
The Striped Dolphin is an extensively studied dolphin that is found in temperate and tropical waters of all the world's oceans.-Taxonomy:...
which has a similar coloration and is found in the same regions.
Fraser's dolphins swim quickly in large tightly packed groups of about 100 to 1000 in number. Often porpoising, the group chop up the water tremendously. The sight of seeing a large group fleeing from a fishing vessels has been reported as "very dramatic".
It is also marked by having the smallest genitalia of any open sea dolphin.
The species feeds on 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...
, 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...
and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
found some distance below the surface of the water (200 metres (656.2 ft) to 500 metres (1,640.4 ft)). Virtually no sunlight penetrates this depth, so feeding is carried out using echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
alone.
Population and distribution
Though only accounted for relatively recently, the number of reported sightings has become substantial—indicating that the species may not be as rare as thought as recently as the 1980s. However the species is still not nearly as well understood as its more coastal cousins. No global population estimates exist.The Dolphin is normally sighted in deep tropical waters; between 30° S and 20° N. The Eastern Pacific is the most reliable site for viewings. Groups of stranded dolphins have been found as far afield as France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
. However these are regarded as anomalous and possibly due to unusual oceanographic
Oceanography
Oceanography , also called oceanology or marine science, is the branch of Earth science that studies the ocean...
conditions, such as El Niño.
The species is also relatively common in the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
but less so in the rest of the Atlantic Ocean.
Conservation
The Southeast Asian populations of Fraser's dolphins are listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMSBonn Convention
The Convention on the Conservation of Migratory Species of Wild Animals aims to conserve terrestrial, marine and avian migratory species throughout their range...
), since they have an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
In addition, Fraser's dolphin is covered by Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU).