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Overview
Brief Summary
Species Abstract
The Black dolphin (scientific name: Cephalorhynchus eutropia), is more commonly known as the Chilean dolphin, is only found in freshwater estuaries, and coastal areas surrounding Chile. It is a marine mammal, a member of the family Delphinidae, part of the order of cetaceans. The species is so named for its black coloring on its fins, tail, and back. It is also known as the Chilean dolphin, Piebald dolphin, Southern dolphin, and White-bellied dolphin.
Because of their preference for shallow coastal waters, these dolphins are often threatened by local fisherman. This dolphin is frequently used in Chile as crab bait, as well as a food source for humans. The species population is decreasing because of this practice, and is now considered Near Threatened. Hunting restrictions have been established in Chile, however, the government has had difficulty enforcing this law in remote areas.
Resembling fellow Cephalorhynchus species, Chilean dolphins are generally described as small and chunky with lengths of about 1.65 meters for both males and females. These dolphins weigh approximately 57 kilograms, females may be slightly larger than males (slight sexual dimorphism). Chilean dolphins have a stout, torpedo-like shape and can have a girth of up to two-thirds of their length. The head is conical in shape and lacks a beak and melon. However, black dolphins have a large number of teeth: 24 to 31 on each side of each jaw.
- Brownell, R., G. Donovan. 1988. Biology of the Genus Cephalorhynchus. Reports of the International Whaling Commision, Special Issue 9: 197-279.
- Mead, James G., and Robert L. Brownell, Jr. / Wilson, Don E., and DeeAnn M. Reeder, eds. 2005. Order Cetacea. Mammal Species of the World: A Taxonomic and Geographic Reference, 3rd ed., vol. 1. 723-743
- Perrin, W. (2010). Cephalorhynchus eutropia Gray, 1846. In: Perrin, W.F. World Cetacea Database. Accessed through: Perrin, W.F. World Cetacea Database
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Distribution
Range Description
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Geographic Range
Chilean dolphins live in the coastal waters of Chile, ranging from near Valparaiso (33°S) to south of Navarino Island (55°15'S) and as far south as Tierra del Fuego. The farthest east that this dolphin has been sighted is near the eastern mouth of the Strait of Magellan.
Biogeographic Regions: pacific ocean (Native )
- Grzimek, B. 2004. Grzimek's Animal Life Encyclopedia. Detroit: Thomson-Gale.
- Ridgway, S., R. Harrison. 1994. Handbook of Marine Mammals. London: Academic Press.
- Brownell, R., G. Donovan. 1988. Biology of the Genus Cephalorhynchus. Reports of the International Whaling Commision, Special Issue 9: 197-279.
- Reeves, R., B. Stewart, P. Clapham, J. Powell. 2002. Sea Mammals of the World. London: A&C Black Publishers.
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UNESCO-IOC Register of Marine Organisms
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
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Physical Description
Morphology
Physical Description
Resembling fellow Cephalorhynchus species, Chilean dolphins are generally described as small and chunky with lengths of about 1.65 m for both males and females. These dolphins weigh approximately 57 kg, females may be slightly larger than males. Chilean dolphins have a stout, torpedo-like shape and can have a girth of up to two-thirds of their length. The head is conical in shape and lacks a beak and melon. The mouth line is fairly long and a groove on the sides of the face is present. The eyes are positioned just behind the mouth. The dorsal fin is low and triangular, with a long leading edge that is almost S-shaped. The flippers are rounded and medium sized. Some animals may also have serrations occurring along the edge of the flippers. Chilean dolphins are dark except for three areas of white on the throat, behind the flippers, and around the anal area. The rest of the body is a complex mix of dark tones. Areas of dark gray cover the flippers, flukes, back and dorsal fin whereas lighter gray tones cover the head and sides. The blowhole may be pale gray.
Chilean dolphins overlap in habitat with Commerson's dolphins (Cephalorhynchus commersonii). They can be distinguished by the lack of a conspicuous white area on the sides and back. Burmeister's porpoises (Phocoena spinipinnis) may also be confused, but they have more slender dorsal fins that are positioned farther back and a lower profile and more pointed peak.
Range mass: 25 to 75 kg.
Average length: 1.6 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger
- Macdonald, D. 1984. The Encyclopedia of mammals. New York: Oxford University Press.
- Jefferson, T., M. Webber, R. Pitman. 2007. Marine Mammals of the World: A Comprehensive Guide to Their Identification. New York: Academic Press.
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Ecology
Habitat
Habitat and Ecology
Most sightings have been near shore and therefore the Chilean dolphin is considered a coastal species, although there has been little survey effort in adjacent offshore waters. Movements appear quite limited, with most dolphins resident in a small area. Individuals identified from natural markings on their dorsal fins have been shown to concentrate their activities in specific bays and channels (Heinrich, 2006; F. Viddi pers. comm., April 2007). Groups tend to be small (between 2 and 15), but relatively large aggregations (20-50) also have been reported (Goodall 1994). Although mixed groups of Chilean and Peale’s dolphins have been observed, a clear pattern of spatial and temporal partitioning of coastal habitat by the two species was documented during a six-year study at Isla Grande de Chiloé (Heinrich 2006). This pattern might not apply in other areas, such as farther south in the Guaitecas Archipelago, where mixed groups are often observed foraging and socializing (F. Viddi pers. comm., April 2007).
Chilean dolphins feed on shallow-water fishes (e.g., sardines, anchovies, rock cod), cephalopods, and crustaceans (Goodall 1994).
Systems
- Freshwater
- Marine
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On Chile's convoluted coastline, Chilean dolphins prefer to live near areas of particularly strong tidal flow above a steep dropping shelf. They are most commonly found in channels and open coasts and bays. They are also found in areas of tide rips at the mouth of fjords. They prefer cold, shallow water at depths of 3 to 15 m. They may also enter rivers and estuaries and can be seen as far as 5 kilometers upstream.
Range depth: 20 to 3 m.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: rivers and streams; coastal ; brackish water
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UNESCO-IOC Register of Marine Organisms
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=1318
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Trophic Strategy
Food Habits
Chilean dolphins commonly feed on small schooling fish, such as sardines (Strangomera bentincki), squid (Loligo gahi, for example), and crustaceans (such as Munida subrugosa). Chilean dolphins which have been observed near salmon hatcheries may eat young, newly released salmon.
Animal Foods: fish; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )
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Associations
Ecosystem Roles
It is unknown how Chilean dolphins impact their ecosystem.
Commensal/Parasitic Species:
- Whale lice
- trematodes (Trematoda)
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Predation
Chilean dolphins are agile and fast swimmers. Natural predation on Chilean dolphins has not been observed, but they may fall prey to sharks and killer whales.
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Life History and Behavior
Behavior
Communication and Perception
Chilean dolphins produce "cries" consisting of rapid pulses at very low levels. Recording equipment at the time was not sufficient to capture the full extent of their sounds. They use echolocation to navigate their environment.
Communication Channels: visual ; acoustic
Perception Channels: visual ; acoustic ; ultrasound ; echolocation
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Life Expectancy
Lifespan/Longevity
Although longevity has not been determined in Chilean dolphins, the related species, Commerson's dolphins and Hector's dolphins have a lifespan of up to 20 years.
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Reproduction
Little is known about the mating system and mating behavior of this species.
Chilean dolphins mate in the early winter and bear young in the spring. Females have one calf every two years. Sexual maturity is reached in 5 to 9 years. Other aspects of Chilean dolphin reproduction are not well understood.
Breeding interval: Females generally have one calf every two years.
Breeding season: Chilean dolphins breed in the winter.
Average number of offspring: 1.
Range age at sexual or reproductive maturity (female): 5 to 9 years.
Range age at sexual or reproductive maturity (male): 5 to 9 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
Female Chilean dolphins invest heavily in young through gestation and lactation. Like other dolphins, young are likely to remain with their parents for long periods during which they learn complex social behaviors, navigation, and foraging.
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female)
- Grzimek, B. 2004. Grzimek's Animal Life Encyclopedia. Detroit: Thomson-Gale.
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Contributor/s
Justification
Bycatch rates are poorly known, several threats in addition to bycatch have been identified, and the species has a restricted range. Therefore, it is urgent that range-wide research be conducted on the current status of this species. Re-assessment should be a high priority once better information becomes available.
History
- 1996Data Deficient
- 1994Insufficiently Known(Groombridge 1994)
- 1990Insufficiently Known(IUCN 1990)
- 1988Insufficiently Known(IUCN Conservation Monitoring Centre 1988)
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Chilean dolphins are listed as near threatened by the IUCN. Exact populations are difficult to measure but populations are considered in decline. Chilean dolphins have been hunted for food and as crab bait for generations. These dolphins are also accidentally caught in coastal gillnets. They also suffer from habitat encroachment by coastal salmon farming. More accurate information on Chilean dolphin populations and the threats they face is needed to formulate a conservation plan.
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: near threatened
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Trends
Population
Population Trend
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Threats
Incidental mortality occurs throughout the range. Although no estimate exists of total incidental mortality in Chile, at Queule, south of Valdivia, Chilean dolphins accounted for nearly half of the dolphins taken in gill nets set from some 30 boats (Reyes and Oporto 1994). This would imply a catch of some 65-70 Chilean dolphins per year at this one port (Goodall 1994). An unknown number of Chilean dolphins are caught in shore-based gillnets set by local people from Isla Chiloé to capture small native fish and introduced farmed salmon that have escaped from their cages (Heinrich 2006).
Aquaculture farms for salmon and shellfish also may have negative effects on Chilean dolphins, e.g. by restricting their movements and eliminating important habitat along the east coast of Isla Grande de Chiloé. Exclusion of Chilean dolphins from bays and fjords is due mainly to large-scale shellfish farming operations but also to salmon farms, although these latter usually are located farther from shore and in deeper water than that preferred by the dolphins (Kemper et al. 2003; Heinrich 2006; Ribeiro et al. 2007). It has been shown that boat traffic, mainly related to aquaculture, affects the behaviour of Chilean dolphins (Ribeiro et al. 2005). Finally, there is evidence that Chilean dolphins are sometimes caught incidentally in anti-sea lion nets set up around salmon farms in the fjords and channels (Francisco Viddi pers. comm., April 2007).
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Management
Conservation Actions
Better information on the status of Chilean dolphins is needed. The species may be declining because of bycatch and the consequences of extensive modification of its limited habitat in Chile. Specifically, it is important to obtain abundance estimates, quantitative information on direct and incidental mortality, and better information on habitat use in relation to aquaculture and other human activities that may degrade or eliminate these dolphins’ habitat. The rapid expansion of salmon (and shellfish) farming in southern Chile is a particular concern. It is also important to evaluate possible gaps in the distribution of Chilean dolphins.
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Relevance to Humans and Ecosystems
Benefits
Economic Importance for Humans: Negative
There are no known adverse effects of Chilean dolphins on humans.
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Economic Importance for Humans: Positive
Chilean dolphins have been hunted in the past for food and as bait for lucrative crab farming. Fisherman use the meat from the dolphins as bait to catch king crabs although this practice is now illegal.
Positive Impacts: food
- IUCN, 2008. "IUCN 2008 Red List" (On-line). IUCN. Accessed April 04, 2009 at http://www.iucnredlist.org/details/4160.
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Risks
IUCN Red List Category
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IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
http://www.marinespecies.org/aphia.php?p=sourcedetails&id=125373
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Wikipedia
Chilean dolphin
The Chilean Dolphin (Cephalorhynchus eutropia), also known as the Black Dolphin, is one of four dolphins in the Cephalorhynchus genus. The dolphin is only found off the coast of Chile, it is commonly referred to in the country as Tunina.[2]
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Physical description
The Chilean Dolphin is a small dolphin at around 1.7 m (5.6 ft) in length, with a blunt head. These characteristics often make for incorrect identification as a porpoise. The 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. The Dolphin has 28-34 pairs of teeth in the upper jaw and 29-33 in the lower.
The 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 ten months to one year and maximum longevity of twenty years.
Population and distribution
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 that the population may be much lower (see also [1] 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 appears to prefer areas of shallow water (less than 200 m depth) and in particular enjoys fast-flowing tidal areas and mouths of rivers.
Conservation
The Chilean dolphin is listed on Appendix II[3] Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II[3] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.[4]
Name
In the early part of the twentieth 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 are now universally agreed in naming the dolphin Chilean on account of its distribution along the coast of the country.
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See also
References
- ^ Reeves, R.R., Crespo, E.A., Dans, Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Pedraza, S., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, JY. & Zhou, K. (2008). "Cephalorhynchus eutropia". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. http://www.iucnredlist.org/apps/redlist/details/4160. Retrieved 18 January 2013.
- ^ Chilean Dolphin Spanish site promoting conservation and awareness of this species.[dead link]
- ^ a b "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.
- ^ Convention on Migratory Species page on the Chilean dolphin
- National Audubon Society: Guide to Marine Mammals of the World ISBN 0-375-41141-0
- Encyclopedia of Marine Mammals ISBN 0-12-551340-2
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