Cephalorhynchus eutropiablack dolphin

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. (Brownell and Donovan, 1988; Grzimek, 2004; Reeves, et al., 2002; Ridgway and Harrison, 1994)

Habitat

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. (Brownell and Donovan, 1988; Grzimek, 2004; Reeves, et al., 2002; Ridgway and Harrison, 1994)

  • Range depth
    20 to 3 m
    65.62 to 9.84 ft

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. (Brownell and Donovan, 1988; Jefferson, et al., 2007; Macdonald, 1984; Reeves, et al., 2002; Ridgway and Harrison, 1994)

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. (Brownell and Donovan, 1988; Jefferson, et al., 2007; Macdonald, 1984; Reeves, et al., 2002; Ridgway and Harrison, 1994)

  • Sexual Dimorphism
  • female larger
  • Range mass
    25 to 75 kg
    55.07 to 165.20 lb
  • Average length
    1.6 m
    5.25 ft

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. (Grzimek, 2004)

  • 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

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

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. (Brownell and Donovan, 1988)

Behavior

Chilean dolphins are usually found in small groups of 2 to 3, although they can be found in groups of up to 20 individuals. Rarely, schools of 20 to 50 individuals have been sighted, particularly in the northern part of their range. In the southern portions of their range, they tend to avoid boats. All reports indicate that these dolphins are extremely shy and difficult to approach. Chilean dolphins have exhibited epimeletic behavior, in which healthy individuals provide assistance to injured individuals. A sub adult female, shot through the heart and aorta, was accompanied by several other animals during the time the animal was brought aboard. The animals then quickly fled after the female was brought out of the water. In contrast, an adult male that was shot was observed to be immediately abandoned by its group. (Brownell and Donovan, 1988; Macdonald, 1984; Reeves, et al., 2002; Ridgway and Harrison, 1994; Wilson and Reeder, 1993)

Home Range

Little is known about the home range and migration patterns of this species, although they are thought to be relatively sedentary.

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. (Brownell and Donovan, 1988; Ridgway and Harrison, 1994)

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. (Reeves, et al., 2002; Ridgway and Harrison, 1994)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

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. (Ridgway and Harrison, 1994)

Ecosystem Roles

It is unknown how Chilean dolphins impact their ecosystem. (Ridgway and Harrison, 1994)

Commensal/Parasitic Species

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. (IUCN, 2008; Reeves, et al., 2002)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no known adverse effects of Chilean dolphins on humans. (IUCN, 2008)

Conservation Status

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. (IUCN, 2008; Reeves, et al., 2002)

Other Comments

Extensive research on Chilean dolphins has yet to be conducted. They were previously called "black dolphins" because specimens that had died were darkened from exposure to air and sun. Animals seen at a distance in the water appeared black as well. This was largely unhelpful and ill-chosen as the species is shades of dark and light gray as opposed to black. (IUCN, 2008; Jefferson, et al., 2007; Reeves, et al., 2002; IUCN, 2008; Jefferson, et al., 2007; Reeves, et al., 2002; IUCN, 2008; Jefferson, et al., 2007; Reeves, et al., 2002)

Contributors

Bob Fan (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web.

Glossary

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

food

A substance that provides both nutrients and energy to a living thing.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

ultrasound

uses sound above the range of human hearing for either navigation or communication or both

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

Brownell, R., G. Donovan. 1988. Biology of the Genus Cephalorhynchus. Reports of the International Whaling Commision, Special Issue 9: 197-279.

Grzimek, B. 2004. Grzimek's Animal Life Encyclopedia. Detroit: Thomson-Gale.

IUCN, 2008. "IUCN 2008 Red List" (On-line). IUCN. Accessed April 04, 2009 at http://www.iucnredlist.org/details/4160.

Jefferson, T., M. Webber, R. Pitman. 2007. Marine Mammals of the World: A Comprehensive Guide to Their Identification. New York: Academic Press.

Macdonald, D. 1984. The Encyclopedia of mammals. New York: Oxford University Press.

Reeves, R., B. Stewart, P. Clapham, J. Powell. 2002. Sea Mammals of the World. London: A&C Black Publishers.

Ridgway, S., R. Harrison. 1994. Handbook of Marine Mammals. London: Academic Press.

Wilson, D., D. Reeder. 1993. Mammal Species of the World; a taxonomic and geographic reference. Washington: Smithsonian Institution Press..