Commerson's dolphin

Commerson's dolphin (Cephalorhynchus commersonii) is also referred to by the common names jacobita, skunk dolphin, piebald dolphin, panda dolphin, or tonina overa (in South America). It is a small oceanic dolphin of the genus Cephalorhynchus. Commerson's dolphin has two geographically isolated but locally common subspecies. The principal subspecies, C.c.commersonii, has sharply-delineated black-and-white patterning and is found around the tip of South America. The secondary subspecies, C.c.kerguelenensis, is larger than C.c.commersonii, has a less-sharply delineated dark and light grey patterning with a white ventral band, and is found around the Kerguelen Islands in the Indian Ocean.

The dolphin is named after French naturalist Dr. Philibert Commerson, who first described them in 1767 after sighting them in the Strait of Magellan.

Two disjunct subspecies of the dolphin are found in geographically disparate areas separated by 130° of longitude and about 8,500 km (5,300 mi); it is not known why they are thus distributed. Global populations are unknown, but the species is accepted to be locally common.

The main subspecies, C.c.commersonii, is found inshore in various inlets in Argentina including Puerto Deseado, in the Strait of Magellan and around Tierra del Fuego, and near the Falkland Islands (Las Malvinas). A survey in 1984 estimated there to be 3,200 individuals in the Strait of Magellan.

Dolphins of the second subspecies, C.c.kerguelenensis, were discovered in the 1950s. They reside near the Kerguelen Islands, in the southern part of the Indian Ocean, and prefer shallow waters.

In 2004, a vagrant individual of unconfirmed origin was sighted on South Africa's Agulhas Bank, 4,200 km (2,600 mi) from the Kerguelen Islands and 6,300 km (3,900 mi) from South America. Though the Kerguelen Islands are closer, such a journey would require swimming against the Antarctic Circumpolar Current.

The commersonii subspecies has a black head, dorsal fin, and fluke, with a white throat and body. The demarcation between the two colours is very clear-cut. This stocky creature is one of the smallest of all cetaceans, growing to around 1.5 m (5 ft). A mature female caught off of southern Patagonia, at 23 kg (51 lb) and 1.36 m (4.5 ft), may be the smallest adult cetacean on record. Its appearance resembles that of a porpoise, but its conspicuous behaviour is typical of a dolphin. The dorsal fin has a long, straight leading edge which ends in a curved tip. The trailing edge is typically concave, but not falcate. The fluke has a notch in the middle.

Sexes are easily distinguished by the different shape of the black blotch on the belly — it is shaped like a teardrop in males, but is more rounded in females. Females reach breeding age at 6 to 9 years. Males reach sexual maturity at about the same age. Mating occurs in the spring and summer and calving occurs after a gestation period of 11 months during the spring and summer. The Commerson's dolphin has been known to live up to 18 years in the wild, while in captivity the oldest individual was at least 33 years old at the time of death.