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
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.
- Habitat Regions
- temperate
- saltwater or marine
- Aquatic Biomes
- rivers and streams
- coastal
- brackish water
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.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- female larger
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- 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
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-independence
-
protecting
- female
-
protecting
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.
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.
- Key Behaviors
- natatorial
- motile
- sedentary
- social
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.
- Perception Channels
- visual
- tactile
- acoustic
- ultrasound
- echolocation
- chemical
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.
- Primary Diet
-
carnivore
- piscivore
- eats non-insect arthropods
- molluscivore
- 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
.
Ecosystem Roles
It is unknown how Chilean dolphins impact their ecosystem.
- Whale lice
- trematodes ( Trematoda )
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
Economic Importance for Humans: Negative
There are no known adverse effects of Chilean dolphins on humans.
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.
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.
Additional Links
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.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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).
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- brackish water
-
areas with salty water, usually in coastal marshes and estuaries.
- 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.
- 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.
- 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).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- 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
- natatorial
-
specialized for swimming
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- social
-
associates with others of its species; forms social groups.
- visual
-
uses sight to communicate
- acoustic
-
uses sound to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- ultrasound
-
uses sound above the range of human hearing for either navigation or communication or both
- 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.
- chemical
-
uses smells or other chemicals to communicate
- food
-
A substance that provides both nutrients and energy to a living thing.
- carnivore
-
an animal that mainly eats meat
- piscivore
-
an animal that mainly eats fish
- molluscivore
-
eats mollusks, members of Phylum Mollusca
References
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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..