Chilean Dolphin
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The Chilean dolphin (''Cephalorhynchus eutropia''), also known as the Black dolphin, is one of four
dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...
s in the genus '' Cephalorhynchus''. The dolphin is found only off the coast of
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
; it is commonly referred to in the country as ''tonina''.


Characteristics


Physical description

The Chilean dolphin is small at around 1.7 metres (5 ft 7 in) in length, with a blunt head. Adults reach up to 60 kg, with females slightly larger than the male bulls. This dolphin is thickly shaped with its girth up to two-thirds its length. Their small and thick shape is often mistaken for other types of porpoises. The
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
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. A black line connects their blowhole, eyes, and dorsal fin. It has 28–34 pairs of teeth in the upper jaw and 29–33 in the lower. The two eyes are positioned at the ends of the mouth lines, giving the appearance of a smile. The tail has a characteristic notch in the middle. The most distinct features of the Chilean dolphin are its short beak, round dorsal fin, and rounded flippers.


Behavior

Unlike other types of dolphins that commonly exhibit social behavior, the Chilean dolphin often remains distant during possible encounters with humans. The Chilean dolphin is normally sighted in small groups of around two to ten individuals, with some larger gatherings of up to 50 individuals occasionally sighted. A group of dolphins is referred to as a pod, school, or
herd A herd is a social group of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with this is called '' herding''. These animals are known as gregarious animals. The term ''herd'' ...
. The species exhibits epimeletic behavior, meaning that when one individual in the pod is injured or sick, healthy members will help take care of the sick.


Communication

Communication between individuals is performed with a series of clicks, whistles, and cries at varying frequencies. Chilean dolphins use echolocation to navigate their surroundings. They are able to perceive visual, tactile, acoustic,
ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...
, echolocation, and chemical information.


Reproduction

Little is known about the reproduction of the Chilean dolphin. They mate in the early winter and females give birth to their
offspring In biology, offspring are the young creation of living organisms, produced either by sexual reproduction, sexual or asexual reproduction. Collective offspring may be known as a brood or progeny. This can refer to a set of simultaneous offspring ...
in the spring. Female dolphins, known as cows, usually have one calf every two to three years. Calves reach full maturity between ages 5 and 9 years. Young calves are cared for by their mothers, where they learn to forage and navigate social behavior.


Lifespan

Longevity Longevity may refer to especially long-lived members of a population, whereas ''life expectancy'' is defined Statistics, statistically as the average number of years remaining at a given age. For example, a population's life expectancy at birth ...
,
gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...
, and
lactation Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The process ...
periods are not known, but are believed to be similar in length to the more studied, and similar, Hector's and
Commerson's dolphin Commerson's dolphin (''Cephalorhynchus commersonii''), also referred to by the common names jacobita, skunk dolphin, piebald dolphin, panda dolphin, or tonina overa (in South America), is a small oceanic dolphin of the genus ''Cephalorhynchus''. ...
s which have a gestation period of about 10 months to one year and maximum longevity of 20 years.


Diet

The Chilean dolphin primarily feeds on sardines, anchovies,
salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...
,
squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...
,
crustaceans Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of Arthropod, arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquat ...
, and
green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
. They swim in a circular or zig-zag pattern to herd the fish that they eat.


Population and distribution

The population of the Chilean dolphin, perhaps one of the least studied of all
cetaceans Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...
, is not known with certainty. It is estimated that less than 5,000 Chilean dolphins remain in the wild. Whatever its number, the Chilean dolphin is
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to the coast of Chile, meaning it is no found anywhere else in the world. They are believed to not migrate. The dolphin is seen over a wider interval of latitudes than other ''Cephalorhynchus'' species – from
Valparaíso Valparaíso () is a major city, Communes of Chile, commune, Port, seaport, and naval base facility in the Valparaíso Region of Chile. Valparaíso was originally named after Valparaíso de Arriba, in Castilla–La Mancha, Castile-La Mancha, Spain ...
at 33°S to
Cape Horn Cape Horn (, ) is the southernmost headland of the Tierra del Fuego archipelago of southern Chile, and is located on the small Hornos Island. Although not the most southerly point of South America (which is Águila Islet), Cape Horn marks the nor ...
at 55°S. Larger groups of 20-–50 are found in the northern areas of its habitat, including reports of a pod. However, the majority of the Chilean dolphins population is found in the southern regions. The species prefers shallow water regions, specifically areas near rivers and high tides. The close association with riverine and estuarine ecosystems makes Chilean dolphins extremely vulnerable to habitat loss both from coastal and upstream river basin degradation. Their relatively limited distribution and need for specific environmental conditions makes the Chilean dolphin particularly susceptible to population loss, even in the most remote areas.


Habitat

The Chilean dolphin is seen over a wider interval of latitudes than other ''Cephalorhynchus'' species — from
Valparaíso Valparaíso () is a major city, Communes of Chile, commune, Port, seaport, and naval base facility in the Valparaíso Region of Chile. Valparaíso was originally named after Valparaíso de Arriba, in Castilla–La Mancha, Castile-La Mancha, Spain ...
at 33°S to
Cape Horn Cape Horn (, ) is the southernmost headland of the Tierra del Fuego archipelago of southern Chile, and is located on the small Hornos Island. Although not the most southerly point of South America (which is Águila Islet), Cape Horn marks the nor ...
at 55°S. In the northern areas, they are found in bays and estuaries with more exposed coastlines, while they prefer fjords and channels in the southern regions. They are commonly seen in bays and channels as well as near rivers and areas with greater changes in
tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...
. Most Chilean dolphins reside in salt water, however they have been spotted in
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
rivers. Additionally, Chilean dolphins prefer shallow waters, usually less than 20 meters, and tend to stay within 500 meters of shore. Research has found that pods are highly localized, and environmental factors often serve as barriers between pods.


Threats

Humans pose the largest threat to the Chilean dolphin population. In addition to being caught for human consumption, the dolphins are also used as bait for long-line sword fishing and crab fisheries. It is reported that between 1,300 and 1,500 Chilean dolphins are harpooned in the
Strait of Magellan The Strait of Magellan (), also called the Straits of Magellan, is a navigable sea route in southern Chile separating mainland South America to the north and the Tierra del Fuego archipelago to the south. Considered the most important natura ...
each year. Use as bait was particularly popular until the 1990s, and hunting of Chilean dolphins is now illegal.
Aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. Nelu ...
farms for salmon, anti-sea lion nets, and boat traffic also pose as threats to the species. Since 2023, at least 14 Chilean dolphins have died as a result of widespread bird flu in Chile. Reports indicate that Chilean dolphins are preyed upon by killer whales and
sharks Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...
. The increase of human activity near the Chilean coastline has also degraded the fragile shallow water habitat.
Hydroelectric dam Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...
s and inter-basin water transfer pose as significant threats to Chilean dolphins residing in freshwater rivers.


Conservation

The Chilean dolphin is listed on Appendix IIAppendix 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: 5 March 2009.
Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II as it has an unfavorable conservation status or would benefit significantly from international co-operation organized by tailored agreements. Initiatives established by Catholic University of the Maule (UCM) and the Environmental Protection Fund FPA of the National Environment Commission (Chile) aim to protect the natural habitat of the Chilean dolphin and provide safe tourism opportunities to view the dolphin.


Name

In the early part of the 20th 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 colors and that its underside was white. The scientific community is now universally agreed in naming the dolphin Chilean on account of its distribution along the coast of the country.


Pictures


See also

* Cetacean Conservation Center * Dolphin Research Center * List of cetaceans *
Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...


References


Further reading

*''National Audubon Society: Guide to Marine Mammals of the World'' *''Encyclopedia of Marine Mammals''


External links


Whale and Dolphin Conservation Societyyaqu pacha - Organization for the Conservation of South American Aquatic Mammals
{{Taxonbar, from=Q755733 Chilean dolphin Mammals of Chile Mammals of Patagonia Chilean dolphin Chilean dolphin Endemic fauna of Chile