Commerson's dolphin
Cephalorhynchus commersonii
Threat Index

Max Length:
Male: 1.70 m
Female: 1.70 m
Calf: 0.65 - 0.75 m

Max Weight:
Male: 86 kg
Female: 86 kg

Est. Population: Unknown

Diet: Fish, squid, crustaceans, benthic invertebrates

IUCN Listing: DD
CMS Appendix: II (South American population)
CITES Appendix: II
Synonym:
Piebald dolphin, Black and white dolphin, Skunk dolphin, Commerson's dolphin

Related Projects:
WDCS Supported project in Argentina

Classification:
Thought to be possibly the most abundant species in the genus Cephalorhynchus, there are two recognised subspecies of Commerson's dolphins; (1) C. c. commersonii - off South America, around Chile, Argentina and the Falkland Islands, and (2) an unamed subspecies around the Kerguelen Archipelago in the southern Indian Ocean.

Appearance:
The Commerson's dolphin is small and stocky; it is shaped more like a porpoise but has distinct dolphin characteristics and behaviour. It has a rounded, conical, blunt head with no beak; large, low, rounded dorsal fin; and flukes with a slight notch and rounded tips. The flippers are small and rounded and, commonly, the left one has serrations along its leading edge, although there are individuals with serrations on both flippers. It has a very distinctive black and white pattern; mostly white with a black head, face and cape, covering the dorsal fin to the flukes. They have a white throat and belly, with a black patch around the genital slit, shaped like a teardrop in males and like an irregular brushstroke in females. Calves are born grey, black and brown. This colouration turns to black and grey as a juvenile, and lightens to become the recognisable black and white of an adult. The colouration of this dolphin is striking and distinctive to each individual, making it a useful method for photoidentification. It is hard to confuse the Commerson's dolphin with other species because of this distinctive black and white pattern, but in poor light it may be confused with either the spectacled porpoise or the Chilean dolphin. Individuals in the Indian Ocean population are generally larger and have more of a grey/black colouration than those found off South America.

Behaviour:
Commerson's dolphins are fast, active swimmers. They are often seen bow-riding, swimming upside down, and spinning underwater. They breach frequently and repeatedly, and they often surf on breaking waves close to shore. They are generally found in small groups of fewer than 10 but can be seen seasonally in groups of up to 100 for feeding or breeding. Highly social animals, they are often seen associating with the Burmeister's porpoise, and the Peale's and Chilean dolphins. They are known to feed on small fish, crabs, octopus, and small crustaceans in kelp beds close to shore and near the seabed.

Distribution:
Commerson's dolphins inhabit the waters off the coast of southern Argentina, around the Malvinas/Falkland Islands, off the south coast of Chile, and around the Kerguelen Islands in the southern Indian Ocean. Most sightings are close to shore in waters less than 100 m deep, often near kelp beds. They also live in estuaries, swimming some distance upriver. Preference for being near to the shore makes Commerson's dolphins more vulnerable to becoming entangled in fishing gear and this is considered to be the major obstacle facing the conservation of this species. In the past they were caught and used as crab bait by Chilean and Argentinean fishermen, although this practice is thought to be less prevalent now. Their total population is not known and the species is listed by IUCN as Data Deficient (2008).