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Cephalorhynchus commersoniiCommerson's dolphin

By Lindsay Peterson and Antonina Salemi

Geographic Range

Commerson's dolphins are primarily found in the coastal waters of the southwest Atlantic Ocean near Patagonia, Tierra del Fuego, Cape Horn and the Falklands Islands. They are most commonly seen along the eastern coast of South American between 41˚30' S and 55˚ S latitude, though they have been found as far north as 31˚ S latitude in some areas.

There is also a disjunct population of Commerson's dolphins in the south Indian Ocean near Kerguelen Island. In this area, they range from 48˚30' S to 49˚45' S latitude and are most common around the Golfe du Morbihan and around Heard Island. They are the only common cetacean in these coastal waters. ("The Commerson's Dolphin Story", 2004; "The Ocean Biogeographic Information System", 2009; "Whales, Dolphins, and Other Marine Mammals of The World", 2006; Goodall, et al., 1988; Goodall, 1994; Leatherwood and Reeves, 1983)

Habitat

Commerson's dolphins inhabit shallow, inshore waters along coastlines, harbors, bays, and river mouths. The live in cold shallow waters, with temperatures ranging from 1˚ C to 16˚ C. They are rarely found at depths greater than 200 m. Commerson's dolphins prefer a neritic environment and are seldom found far offshore. Most sightings occur in the coastal regions near the mouths of bays and estuaries or over the wide shallow continental shelf where the tidal range is great. Commerson's dolphins move towards the shore with the tide. In some areas, dolphins prefer areas with the strongest currents - up to or greater than 15 km/hr. They are also frequently found in kelp beds and in narrow passages like those found in the Strait of Magellan. It is thought that most dolphins seasonally move away from the shore, following fish which move offshore during the winter. Commerson's dolphins in Kerguelen follow this trend and are less common inshore between June and December. In Kerguelen, they are most commonly observed over the Kerguelen shelf, but they are also found in open waters, kelp-ringed coastlines, and protected areas between islets. ("The Commerson's Dolphin Story", 2004; "Whales, Dolphins, and Other Marine Mammals of The World", 2006; Clapman, et al., 2002; Goodall, et al., 1988; Goodall, 1994; Leatherwood, et al., 1988)

  • Range depth
    200 (high) m
    656.17 (high) ft

Physical Description

Commerson's dolphins are mostly white and have black marked faces and bodies. This black and white pattern varies with geographic location as well as age and sex. These colors are more muted in coastal waters. The black color on the head extends behind the blowhole and down the sides of the body, including the flippers. Black also covers the dorsal fin and runs back to encircle the tailstock behind the anus and flukes. The black color on the chest ends in a posterior-facing point. Large black genital patches are oval or heart-shaped, with the narrow end pointing posteriorly in males. In females the narrow end is anterior, and may or may not include "ears" outside the mammary slits. The throat is generally white, as is the rest of the body. Individuals can be recognized by varying shape of the black "widow's peak" behind the blowhole as well as pigmentation on the side of the tailstock. Calves are born dark grey and black with vertical creasing as a result of fetal folding. These folds disappear after a week, and the dark grey portions become paler in the first few months and white within 4 to 6 months. ("Whale Watcher", 2006; Goodall, et al., 1988)

Coloration of Commerson's dolphins near Kerguelen Island is similiar to that of juveniles from the south Atlantic Ocean. Near Kerguelen, the surface in front of the dorsal fin is grey, as are the sides. The grey behind the blowhole is streaked with black and their "widow's peak" is not as well defined. The white throat patch is more asymmetrical than in individuals from the south Atlantic. Commerson's dolphins near Kerguelen generally have a narrow white line in the center of their chest, a feature seldom found in their counterparts in the south Atlantic Ocean. (Goodall, et al., 1988; Goodall, 1994)

Commerson's dolphins have a dark rounded dorsal fin that rises at a shallow angle and flippers with rounded tips. Their head is blunt and has a sloped forehead and little or no beak. A narrow cap extends on the rear half of body from dorsal fin to flukes. The tail flukes are slightly round tipped and notched, and the flippers are small and rounded. The flukes have concave edges with a slight hatch in the middle with dark coloring above and below. Commerson's dolphins have approximately 29 to 30 pairs of pointed teeth in the upper and lower jaws. Newborns range from 0.5 to 0.75 m in length and weigh 4.5 to 7.3 kg. Adults range from 1.2 to 1.5 meters in length and usually weigh 35 to 65 kg. Females are generally larger than males, and Commerson's dolphins from the Indian Ocean tend to be larger than those in the South Atlantic. Also, although Commerson's dolphins from both areas do not have well defined snouts, there is a distinct rostral depression in Kerguelen animals which individuals in the south Atlantic lack. ("Whale Watcher", 2006; Goodall, et al., 1988; Leatherwood and Reeves, 1983; Lockyer, et al., 1988)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range mass
    35 to 65 kg
    77.09 to 143.17 lb
  • Range length
    1.2 to 1.5 m
    3.94 to 4.92 ft

Reproduction

Little information is available regarding the mating systems of Commerson's dolphins. They have been observed copulating in a vertical, belly to belly position. (Goodall, et al., 1988)

Commerson's dolphins breed between the months of September and February. After a gestation period of at most 12 months, females give birth to one individual in the winter. Calves are born tail first and are grey in color. Newborns range from 0.5 to 0.75 m in length and weigh 4.5 to 7.3 kg. Their dorsal fin and tail flukes are pliable at birth and gradually stiffen as they mature. The length of the nursing period in the wild is unknown. However, in captivity calves begin eating solid food by 2 months of age and take whole fish by 4 months. Males typically reach sexual maturity between 6 and 9 years of age, and females between 5 and 9 years. Individuals from the the south Atlantic Ocean, however, tend to reach sexual maturity at a younger age than populations from Kerguelen. ("The Commerson's Dolphin Story", 2004; Goodall, et al., 1988; Repetto and Wurtz, 2003)

  • Breeding interval
    Commerson's dolphins breed once yearly.
  • Breeding season
    Mating occurs between late September and early February.
  • Range number of offspring
    1 (high)
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    10 to 12 months
  • Range age at sexual or reproductive maturity (female)
    5 to 8 years
  • Range age at sexual or reproductive maturity (male)
    6 to 9 years

Mother Commerson's dolphins nurse their calves through abdominal mammary slits for about 9 months. Mothers are attentive to their calves, which swim close to their mother. Calves learn to swim by following in their mother's slip stream. Females also appear defensive of their young. ("The Commerson's Dolphin Story", 2004; Repetto and Wurtz, 2003)

  • Parental Investment
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Commerson's dolphins generally do not live more than 10 years in the wild. In captivity, they commonly live to 18 years of age, and one individual at SeaWorld San Diego lived to be 25.8 years of age. ("The Commerson's Dolphin Story", 2004; "Whale Watcher", 2006; "Whales, Dolphins, and Other Marine Mammals of The World", 2006; Clapman, et al., 2002; de Magalhaes and Costa, 2009)

  • Range lifespan
    Status: wild
    23 (high) years
  • Range lifespan
    Status: captivity
    25.8 (high) years
  • Typical lifespan
    Status: wild
    10 (high) years
  • Typical lifespan
    Status: captivity
    15 to 18 years

Behavior

Commerson's dolphins are usually found in groups of only 1 or 3 individuals, but may socialize in groups as large as 100. One group in captivity was controlled by a dominant male, and other less aggressive males often resided in an adjacent pool. A calf in captivity became synchronized to its mother's swimming immeditaely after birth. When another female tried to "adopt" the calf, the mother appeared defensive of her young. ("The Commerson's Dolphin Story", 2004; Clapman, et al., 2002; Goodall, 1994)

Commerson's dolphins are sometimes seen feeding alone along boundaries of adjacent currents, but they are more commonly observed cooperatively feeding. Two main types of herding are used. In one type, a group of 15 or fewer dolphins form a half circle and drive a school of fish against the shore. Sometimes, a dolphin is temporarily stranded on shore as well, but stranded dolphins are usually able to return to the sea on their own. The other type of herding does not involve the use of the shore as a barrier. In groups of 2 to 6, Commerson's dolphins circle around a group of fish and take turns passing through the center of the circle, feeding and then returning to the perimeter of the circle. (Goodall, et al., 1988)

Commerson's dolphins are known for their high-speed swimming, routinely reaching speeds of 11 to 13 kph. They ride all four types of waves described by Hertel in 1969: wind waves at sea, breaking shore waves, bow waves of vessels and other waves of vessels, including stern wakes. There are various accounts of aerial acrobatics, such as vertical leaps in Commerson's dolphins. They often swim on their back, and they spin underwater on their longitudinal axes behind the pressure waves of vessels. Commerson's dolphins are considered playful swimmers. On a number of occasions, they have been observed pushing objects, such as inflated inner tubes, around a bay and onto the beach. They have also been observed surfacing under and nudging birds off of a rig. ("The Commerson's Dolphin Story", 2004; Clapman, et al., 2002; Goodall, et al., 1988; Leatherwood, et al., 1988)

In South America, Commerson's dolphins have been seen swimming near and interacting with numerous birds and other marine mammals. Like other dolphins, their presence is often announced by flocks of birds overhead (usually terns). Commerson's dolphins commonly assiciate with Peale's dolphins, swimming synchronously for long periods, feeding in similiar areas, and riding the waves of the same vessels. They also commonly associate with southern sea lions. (Goodall, et al., 1988)

Home Range

Little information is available regarding the home range of Commerson's dolphins.

Communication and Perception

Commerson's dolphins communicate using echolocation. They also rely on echolocation to navigate and hunt through dark waters. In captivity, they vocalize at frequencies ranging from 120 to 134 kHz for a duration of 180 to 600 μs. ("The Commerson's Dolphin Story", 2004; Repetto and Wurtz, 2003)

Food Habits

Commerson's dolphins are primarily carnivores but are often opportunistic coastal feeders. They rely on both pelagic and benthic prey. Their diet is mainly composed of mysid shrimp, and small fish like silversides, sardines, and Argentine hake. They are also known to eat squid, octopus, marine worms, tunicates, and even algae. Among 53 Commerson's dolphins in the Tierra del Fuego, 22.5% of their diet was composed of mysid shrimp, 20.4% of 3 species of fish, 14.1% of squid, and the rest of algea, isopods, and other benthic invertebrates. Other plant remains, seeds, sand, and pebbles were also found in their stomachs. Individuals found near the Kerguelen Island eat a high proportion of semipelagic chaennichthyid fish, as well as pelagic and benthic crustaceans. At times, Commerson's dolphins hunt together, as described in the behavior section. In captivity, Commerson's Dolphins consume 3 to 4 kg of Atlantic herring each day. (Bastida, et al., 1988; Clapman, et al., 2002)

In areas of high tides, Commerson's dolphins feed in the shallow areas in or just beyond the advancing tide breakers in order to take fish, such as sardines and anchovies that are also feeding in the area, or other organisms that are dislodged by the turbulent water. Commerson's dolphins also feed for long periods in kelp beds, in open waters, around submarine banks, and near artificial structures such as piers and oil rigs. (Goodall, et al., 1988; Goodall, 1994)

  • Animal Foods
  • fish
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • Plant Foods
  • algae

Predation

The black and white coloration patterns of Commerson's dolphins breaks up the outline of their body, making them more difficult for predators to spot. Natural predators may include killer whales, sharks, and leopard seals that live within the same geographic range, but such predation has not been documented. Humans actively kill Commerson's dolphins for food, oil and bait and inadvertently through other fishing practices. ("The Commerson's Dolphin Story", 2004; Clapman, et al., 2002)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators
    • Humans Homo sapien

Ecosystem Roles

Commerson's dolphins prey on small fish, mysid shrimp, as well as squid, octopus, marine worms, and tunicates. While natural predators are still unknown, killer whales and leopard seals may prey on them as they are found in the same geological area. Commerson's dolphins also act as hosts for roundworms (Nematoda) and flukes (Trematoda). ("The Commerson's Dolphin Story", 2004; "The Encyclopedia of Earth", 2010)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Humans living in Patagonia and Tierra del Fuego have traditionally harpooned Commerson's dolphins for their meat and oil. Crab fishermen in southern Argentina and Chile use the meat of Commerson's dolphins as bait, as it does not deteriorate in salt water. These practices are now illegal and have steadily declined. Commerson's dolphins can also be found in aquariums in Germany, Japan and the United States. ("The Commerson's Dolphin Story", 2004; "The Encyclopedia of Earth", 2010; Clapman, et al., 2002; Goodall, et al., 1988)

Economic Importance for Humans: Negative

Commerson's dolphins may affect fishermen, as they sometimes become entangled in fishing nets and may also deplete populations of small fish.

Conservation Status

Commerson's dolphins were hunted for their meat and oil and more recently for crab bait. Although these practices are now illegal, they are often entangled in gillnets and other fishing gear used in nearshore waters and are occasionally killed in midwater trawl nets used for shrimp. In Tierra del Fuego alone, at least 5 to 30 dolphins die each year as by-catch in nets set perpendicular to the shore.

Near Kerguelen Island, low levels of chlorinated hydrocarbons (DDT, PCB and HCB) were found in the blubber of Commerson's dolphins, confirming the presence of pollutants in oceans far from their main source. The levels of contaminants were 10 to 100 times that of cetaceans in the North Atlantic. ("The Commerson's Dolphin Story", 2004; Clapman, et al., 2002; Goodall, 1994)

Contributors

Lindsay Peterson (author), San Diego Mesa College, Antonina Salemi (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Tanya Dewey (editor), University of Michigan-Ann Arbor, Gail McCormick (editor), Animal Diversity Web Staff.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

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.

World Map

acoustic

uses sound to communicate

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

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.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

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.

female parental care

parental care is carried out by females

food

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

freshwater

mainly lives in water that is not salty.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

migratory

makes seasonal movements between breeding and wintering grounds

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.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

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

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

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

2004. The Commerson's Dolphin Story. San Diego: Sea World, Inc.

1983. The Sierra Club Handbook of Whales and Dolphins. San Francisco: Sierra Book Clubs.

2006. Whale Watcher. United Kingdom: Firefly Books, Ltd..

2006. Whales, Dolphins, and Other Marine Mammals of The World. United States: University Presses of California.

Boris Cullk. 2010. "Convention of Migratory Species" (On-line). Accessed March 15, 2010 at http://www.cms.int/reports/small_cetaceans/data/c_commersonii/c_commersonii.htm.

2010. "The Encyclopedia of Earth" (On-line). Accessed March 15, 2010 at http://eoearth.org/article/Commerson%27s_dolphin.

2010. "The IUCN Red List of Threatened Species" (On-line). Accessed March 15, 2010 at http://www.iucnredlist.org/apps/redlist/details/4159/0.

2009. "The Ocean Biogeographic Information System" (On-line). Accessed March 15, 2010 at http://seamap.env.duke.edu/species/tsn/180449.

Bastida, R., V. Lechtschein, R. Goodall. 1988. Food habits of Cephalorynchus commersonii off Tierra del Fuego.. Pp. 143-161 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).

Clapman, P., R. Reeves, B. Stewart, J. Powell. 2002. National Audubon Society: Guide to Marine Mammals of the World. New York: Random House.

Goodall, R. 1994. Commerson's dolphin. Pp. 241-267 in S Ridgway, R Harrison, eds. Handbook of Marine Mammals, Vol. Volume 5: The First Book of Dolphins. San Diego: Academic Press Limited.

Goodall, R., A. Galeazzi, S. Leatherwood, K. Miller, I. Cameron, R. Kastelein, A. Sobral. 1988. Studies of Commerson's dolphins, Cephalorynchus commersonii, off Tieraa del Fuego, 1976-1984, with a review of information on the speices in the South Atlantic. Pp. 3-70 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).

Leatherwood, S., R. Kastelein, K. Miller. 1988. Observations of Commerson's dophin and other cetaceans in south Chile, Janurary-February 1984. Pp. 71-84 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).

Leatherwood, S., R. Reeves. 1983. he Sierra Club Handbook of Whales and Dolphins. San Francisco: Sierra Club Books.

Lockyer, C., R. Goodall, A. Galeazzi. 1988. Age and bodylength characteristics of Cephalorynchus commersonii from incidentally-caught specimens off Tierra del Fuego. Pp. 103-118 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).

Repetto, N., M. Wurtz. 2003. Underwater World: Dolphins and Whales.. Italy: While Star Publishers.

Webber, M. 1993. FAO Species Identification Guide. Marine Mammals of the World. Rome: FAO.

de Magalhaes, J., J. Costa. 2009. A database of vertebrate longevity records and their relation to other life-history traits. Journal of Evolutionary Biology, 22(8): 1770-1774. Accessed March 24, 2011 at http://genomics.senescence.info/species/entry.php?species=Cephalorhynchus_commersonii.

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