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Overview

Brief Summary

Biology

The preference of Fraser's dolphin for deep waters is due to the prey on which it feeds; fish, squid and crustacean species that inhabit the deeper waters of the oceans. Feeding on such food requires Fraser's dolphin to dive down to depths of at least 250 to 500 metres to hunt. It is thought that Fraser's dolphin itself may be occasional prey for killer whales, false killer whales and large sharks, and circular wounds caused by the peculiar cookie-cutter shark (Isistius brasiliensis) have been found on this species (2) (3). Fraser's dolphins are highly sociable mammals that swim around in tightly-bonded schools of 100 to 1,000 individuals (2) (6), often together with schools of melon-headed whales (Peponocephala electra), other dolphin species (2) (3), or in some areas, such as the Sulu Sea, with short-finned pilot whales (Globicephala macrorhynchus) (7). A school of Fraser's dolphins moves quickly, on very rare occasions riding the bow waves of boats, and with members of the school frequently porpoising; the term used to describe a dolphin leaping clear of the water when surfacing to breathe (2) (3). Mating in Fraser's dolphin is believed to be promiscuous, and mature females give birth approximately every two years to a metre-long calf, after a gestation period of 12.5 months. Males reach sexual maturity at an age of seven to ten years, while females are able to reproduce at five to eight years of age (2).
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Description

This tropical dolphin was scientifically described in 1956 from an individual washed up on a beach in Borneo (2), but was not actually recorded alive until the 1970s (5). Fraser's dolphin can be identified by its stocky body and short beak, and by its small flippers, tail fin and triangular or slightly curved dorsal fin. The body bears a striking colour pattern, but one that varies with both age and sex. The back is brownish-grey, the lower sides of the body cream-coloured, and the belly is white or pink. A prominent black stripe runs along the side of the body from the eye to the anus; in adult males this is thick, while in adult females it is variable and in young dolphins the stripe is faint or completely absent. The same pattern occurs with a black stripe on the face; this is absent in calves and variable in females, while on adult males it is extensive and merges with the body stripe to form a 'bandit mask' (2).
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Description

Shyness is as good an explanation as any: Fraser’s dolphins were first collected as scientific specimens in the 1970s. They are found in tropical waters in many parts of the world, but tend to flee from ships. They also quickly die in captivity. They are striking animals, with a very short beak, small dorsal fin, small flippers, and a broad black streak along the side. At a distance, thThey can be mistaken for striped dolphins, which also have a stripe along the side. Most of the fish they feed on stay deep underwater, which suggests that the dolphins make deep dives to feed. They are seen in schools of 100-1,000, but not enough is known about their natural history to say whether these groups are male, female, or mixed-sex groups. Newborns are about a meter long.

Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account
  • Original description: Fraser, F.C., 1956.  A new Sarawak dolphin, p. 496.   Sarawak Museum Journal, 7:478-503.
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Distribution

These dolphins are restricted to tropical and subtropical waters.

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

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Range Description

The exact distribution of this species is poorly known. Fraser's Dolphin has a pantropical distribution, largely between 30°N and 30°S in all three major oceans (Jefferson and Leatherwood 1994, Dolar 2002). Strandings in temperate areas (Victoria in Australia, Brittany and Uruguay) may represent extralimital forays connected with temporary oceanographic anomalies such as the world-wide El Niño phenomenon in 1983–84, during which a mass stranding occurred in France (Perrin et al. 1994). Bones et al. (1998) reported on a stranding on the coast of Scotland.

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.
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pantropical
  • UNESCO-IOC Register of Marine Organisms
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Range

Fraser's dolphin is a tropical species distributed in oceans between latitudes of 30°N and 30°S (2).
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Physical Description

Morphology

Other Physical Features: endothermic ; bilateral symmetry

Average mass: 164000 g.

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Size

Size in North America

Length:
Range: 2.3-2.7 m males; 2.1-2.6 m females

Weight:
Range: 164-209 kg
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
It is an oceanic species that prefers deep offshore waters, but it can be seen near shore in some areas where deep water approaches the coast (such as the Philippines, Taiwan, and some islands of the Caribbean and the Indo-Malay archipelago) (Perrin et al. 1994).

In the eastern tropical Pacific, it occurs more often in Equatorial - southern subtropical surface water and other waters typified by upwelling and generally more variable conditions (Au and Perryman 1985). Off South Africa, records are associated with the warm Agulhas Current that moves south in the summer (Perrin et al. 1994).

Fraser's Dolphins feed on midwater fish (especially myctophids), squid, and crustaceans (Dolar et al. 2003). Physiological studies indicate that Fraser’s are capable of quite deep diving (and it is thought that they do most of their feeding deep in the water column – in waters up to 600 m deep), but they have been observed to feed near the surface as well (Watkins et al. 1994).

Systems
  • Marine
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oceanic
  • UNESCO-IOC Register of Marine Organisms
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Depth range based on 50 specimens in 1 taxon.
Water temperature and chemistry ranges based on 50 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 20.220 - 28.679
  Nitrate (umol/L): 0.050 - 7.245
  Salinity (PPS): 33.325 - 36.385
  Oxygen (ml/l): 4.437 - 5.288
  Phosphate (umol/l): 0.063 - 0.897
  Silicate (umol/l): 0.838 - 6.847

Graphical representation

Temperature range (°C): 20.220 - 28.679

Nitrate (umol/L): 0.050 - 7.245

Salinity (PPS): 33.325 - 36.385

Oxygen (ml/l): 4.437 - 5.288

Phosphate (umol/l): 0.063 - 0.897

Silicate (umol/l): 0.838 - 6.847
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Inhabits deep, oceanic waters except in places where deep water approaches the coast, such as in the Philippines and Indonesia (2).
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Trophic Strategy

Fraser's dolphins primarily eat fish, but they also feed on squid, cuttlefish and shrimp. There is strong evidence that these animals prefer to feed at depths of 250-500 meters and rarely at the surface.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

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Life History and Behavior

Behavior

Perception Channels: tactile ; chemical

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Life Expectancy

Lifespan, longevity, and ageing

Observations: In one study in the wild, of ten specimens caught, the oldest was estimated to be 16 years old (Jefferson and Leatherwood 1994). Maximum longevity is unknown.
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Reproduction

Breeding appears to be year-round with a possible peak in the summer months. The gestation period is thought to be about 11 months. Sexual maturity of both sexes occurs at about seven years of age. There is no sexual dimorphism except in the size and shape of the dorsal-fin, with male fins being larger than female fins.

Breeding season: Breeding appears to be year-round with a possible peak in the summer months.

Average gestation period: 11 months.

Average age at sexual or reproductive maturity (female): 7 years.

Average age at sexual or reproductive maturity (male): 7 years.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

Average gestation period: 335 days.

Average number of offspring: 1.

Average age at sexual or reproductive maturity (female)

Sex: female:
2646 days.

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Conservation

Conservation Status

CITES Appendix 2

IUCN Red List of Threatened Species: least concern

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K.A., Karkzmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y. , Wells, R.S. & Wilson, B.

Reviewer/s
Rojas-Bracho, L. & Smith, B.D.

Contributor/s

Justification
The species is widespread and abundant (with current population estimates around 300,000) and there have been no reported population declines or major threats identified.

History
  • 1996
    Data Deficient
  • 1994
    Insufficiently Known
    (Groombridge 1994)
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Status

Classified as Least Concern (LC) on the IUCN Red List (1), and listed on Appendix II of CITES (4).
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Population

Population
There are estimated to be about 289,300 (CV=34%) Fraser’s Dolphins in the eastern tropical Pacific (Wade and Gerrodette 1993, Perrin et al. 1994), and 16,836 (CV=11%) in Hawaiian waters (Carretta et al. 2006). In the eastern Sulu Sea, Dolar et al. (2006) estimated a total abundance of 13,518 (CV=27%) Fraser’s Dolphins. About 726 (CV=70%) were estimated present in the northern Gulf of Mexico (Waring et al. 2006).

Population Trend
Unknown
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Threats

Major Threats
Small numbers of Fraser's Dolphins are taken regularly or opportunistically by harpoon in the Lesser Antilles, Sri Lanka, Indonesia (Kahn 2004), the Philippines, Taiwan and probably elsewhere in the Indo-Pacific (Jefferson and Leatherwood 1994). A few have been taken in drive fisheries in Taiwan and Japan (Perrin et al. 1994). Dolar et al. (1994) investigated directed fisheries for marine mammals in central and southern Visayas, northern Mindanao and Palawan, Philippines. Some of the hunters take only dolphins, for bait or human consumption and the species taken include Fraser's Dolphins. Around 800 cetaceans are taken annually by hunters at the seven sites, mostly during the inter-monsoonal period of February-May.

Some Fraser’s Dolphins are killed incidentally in the tuna purse-seine fishery in the eastern tropical Pacific (Gerrodette and Wade 1991): 26 were estimated taken during the period 1971–75. A few are also taken in gill nets in Sri Lanka, the Philippines, and likely in other tropical gillnet fisheries as well. Some are killed by anti-shark nets in South Africa (Perrin et al. 1994, Cockcroft 1990). Other incidental catches in purse seines (Philippines), gillnets, driftnets (Taiwan), and trap nets (Japan) are also known (Jefferson and Leatherwood 1994).
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While poorly-known, Fraser's dolphin is believed to be reasonably abundant due to the incredibly large schools that have been observed (1). In certain areas, however, it remains vulnerable to the threat of hunting and by-catch. In the lower Antilles, Indonesia and (before its protection) the Philippines, this species has been killed by harpoon and its meat consumed or sold in local markets. Some are also taken in fisheries in Taiwan and Japan, and in many areas Fraser's dolphin is caught unintentionally in fishing gear (2) (8).
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Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES

The Southeast Asian subpopulations are listed in Appendix II of CMS. Subpopulation structure and the impact of direct and incidental takes require further investigation.
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Conservation

The south-east Asian populations of Fraser's dolphin are listed on Appendix II of the Convention on Migratory Species (CMS), meaning that this species would significantly benefit from international cooperation. CMS encourages the range states to develop agreements that will benefit the conservation of this species (9). In 1992, the Department of Agriculture of the Philippines banned the 'taking or catching, selling, purchasing, possessing, transporting and exporting of dolphins'. This order has not stopped dolphin hunting, but seems to have decreased the sale of dolphin meat openly in the market (8). The distribution, migratory behaviour, abundance and by-catch rates of Fraser's dolphin are poorly known (8), and thus further research into this sociable dolphin is likely to be the first step in the development of any conservation measures.
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Relevance to Humans and Ecosystems

Benefits

Because they do not feed at the surface, they do not compete with fisherman for tuna or other pelagic fish.

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People in many Asian cultures hunt this species for food.

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Risks

IUCN Red List Category

Least Concern (LC)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

Fraser's dolphin

Fraser's dolphin (Lagenodelphis hosei) 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.

Taxonomy[edit]

In 1895, Charles E. Hose found a skull on a beach in Sarawak, Borneo. He donated it to the British Museum. The skull remained unstudied until 1956 when Francis Fraser[1] examined it and concluded that it was similar to species in both the genera Lagenorhynchus and Delphinus 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.

Description[edit]

Fraser's dolphins are about 1 m (3 ft 3 in) long and 20 kg (44 lb) weight at birth, growing to 2.75 m (9 ft 0 in) and 200 kg (440 lb) at adulthood. They have a stocky build, a small fin in relation to the size of the body, conspicuously small flippers. The dorsal fin 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 m/660 ft to 500 m/1,600 ft). Virtually no sunlight penetrates this depth, so feeding is carried out using echolocation alone.

Population and distribution[edit]

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 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.

Conservation[edit]

The Southeast Asian populations of Fraser's dolphins are listed on Appendix II [2] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), since they have an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.[3]

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)[4] and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macronesia (Western African Aquatic Mammals MoU).[5]

See also[edit]

References[edit]

  1. ^ Marshall, N. B. (1979). "Francis Charles Fraser. 16 June 1903-21 October 1978". Biographical Memoirs of Fellows of the Royal Society 25: 287–226. doi:10.1098/rsbm.1979.0010.  edit
  2. ^ "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009.
  3. ^ Convention on Migratory Species page on the Fraser's dolphin
  4. ^ Pacific Cetaceans MoU
  5. ^ Western African Aquatic Mammals MoU

Further reading[edit]

  • Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. (2008). Lagenodelphis hosei. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 26 February 2009. Database entry includes justification for why this species is listed as data deficient
  • Whales Dolphins and Porpoises, Mark Carwardine, Dorling Kindersley Handbooks, ISBN 0-7513-2781-6
  • National Audubon Society Guide to Marine Mammals of the World, Reeves, Stewart, Clapham and Powell, ISBN 0-375-41141-0
  • Malaysian Naturalist, Vol 59/3 - 2006, page 5.
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