Commerson’s Dolphin (Cephalorhynchus commersonii)
Commerson’s Dolphin is one of four dolphins in the Cephalorhynchus genus. The species has also the common names Skunk Dolphin and Piebald Dolphin. Commerson’s Dolphin has a very distinctive patterning. It has a black head, dorsal fin, and fluke, with a white throat and body. The definition between the two colours is very clear-cut. In shape and size this dolphin is stocky and grows to around 1.5 metres. Its appearance resembles that of a porpoise, but its conspicuous behaviour is typical of a dolphin.
Their dorsal fin has a long, straight leading edge which ends in a curved tip. The fluke has a notch in the middle. This dolphin has no beak.
Commerson’s Dolphin Behaviour
The Commerson’s Dolphin is very active. It is often seen swimming rapidly on the surface and leaping from the water. It also spins and twists as it swims and may surf on breaking waves when very close to the shore. The Commerson’s Dolphin will bow-ride and swim behind fast-moving boats.
Commerson’s Dolphin Diet
The Commerson’s Dolphin feeds on a mix of coastal and pelagic fish and squid. Those in the South American sub-population supplement their diet with crustaceans.
Commerson’s Dolphin Distribution
The Commerson’s Dolphin is distributed in two locations. The larger population is found inshore in various inlets in Argentina, in the Strait of Magellan and near the Falkland Islands. The second population resides near the Kerguelen Islands, 8,000 kilometres to the east of their nearest special cousins. They prefer shallow waters. Global populations are unknown, but the species is accepted to be locally common. A survey in 1984 estimated there to be 3,400 individuals in the Strait of Magellan.
Commerson’s Dolphin Reproduction
Females reach breeding age at 6 to 9 years. Males reach sexual maturation at about the same age. Mating occurs in the spring and summer and calving occurs after a gestation period of 11 months. The oldest known Commerson’s Dolphin died at age 18.
Commerson’s Dolphin Conservation
The IUCN lists Commerson’s Dolphin as data deficient in its Red List of Threatened Species. The proximity of the dolphin to the shore makes accidental killing in gillnets a common occurrence. The dolphin was killed for use as crab bait by some Argentinian and Chilean fishermen in the 1970s and 80s. This practice has been reduced.