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Commerson's dolphins are a small and very distinctive species with mostly black on the head, fin and flipper regions and mostly white in the other areas of the body. Young Commerson's are usually brown or black and gray for the first four to five months. The dorsal fin is small and rounded at the tip and the beak is small or unnoticeable.
In this species, females are typically larger than males.
These are one of the smallest dolphins reaching lengths of up to 1.2-1.7 m (3.9-5.6 ft). Newborn calves are approximately 55-65 cm (21.7-25.6 in) in length.
Commerson's dolphins can reach weights of up to 35-60 kg (77-132 lbs). At birth, calves average 4.5-5.5 kg (10-12 lbs).
Feeds on krill, cuttlefish, squid, shrimp and small fishes
Gestation lasts a maximum of approximately 12 months.
Between late winter and early spring
Unknown; at least 4 or more months
From the tip of South America (Peninsula Valdes to Tierra del Fuego), through the Strait of Magellan, around the Falkland Islands and the Kerguelen Islands. There are two populations of Commerson's dolphins; the population off the coast of southern South America and another population found around the Kerguelen Islands, which is considered a distinct subspecies.
Typically found in shallow, coastal waters of the sub-Antarctic.
Listed as Data Deficient
Commerson's dolphins typically eat 3.5-6 kg (8-13 lbs) of food per day. This is proportionally a much greater amount than either killer whales or bottlenose dolphins ingest each day, and is due to Commerson's having a metabolic rate that is two to three times higher than many other whale or dolphin species.
The first Commerson's dolphin calf ever born in a marine zoological environment was born at SeaWorld San Diego on February 21, 1985. The calf weighed approximately 9 kg (20 lbs) and measured 61 cm (2 ft).
Commerson's dolphins are fast and highly maneuverable cetaceans regularly swimming at speeds of 11-13 kph (7-8 mph). These dolphins are commonly seen wave-riding in the bows or wakes of high-speed boats, shoreline breakers or groundswells.
Commerson's dolphins are typically found alone or in small groups of two to three animals and occasionally spotted in larger groups of 20-30 or more dolphins. They often hunt cooperatively either encircling fish and taking turns passing through to feed on the clustered fish or even driving fish onshore and temporarily stranding themselves to snatch up the fish.
ECOLOGY AND CONSERVATION
Within their range, Commerson's dolphins are considered fairly common. However, some are inadvertently caught and killed in fishing nets throughout part of their range, especially off the coast of Argentina. In the past, local fishermen intentionally caught these dolphins for food, oil or bait. Now that this practice is illegal, the rate of hunting for Commerson's dolphins has allegedly declined. Yet, it is not known how much the accidental catch from Commerson's entangled in fishing gear still continues to affect population numbers. In some parts of their range, Commerson's dolphins have been found with elevated levels of industrial pollutants, which may also pose a threat to population numbers.
As with other species of cetaceans, international laws protect Commerson's dolphins.
Jefferson, T.J. Leatherwood, S. and M.A. Webber.
FAO Species identification Guide. Marine Mammals of the World
. Rome. FAO, 1993.
Leatherwood, Stephen, and Reeves, Randall R.
The Sierra Club Handbook of Whales and Dolphins
. San Francisco: Sierra Club Books, 1983.
The Commerson's Dolphin Story
. San Diego. Sea World, Inc. 2004.
Reeves, R. R., Stewart, B.S., Clapman, P.J., and J.A. Powell (Peter Folkens illustrator).
National Audubon Society: Guide to Marine Mammals of the World
. New York: Random House, 2002.