Cephalorhynchus Dolphin

 

Common Name: Southern Dolphins

Class: Mammalia

Order: Cetacea

Family: Delphinidae

Genus: Cephalorhynchus

Species: Four species:

      Commerson's dolphin C. commersoni 

      Heaviside's dolphin C. heavisidii 

      Hector's dolphin C. hectori 

      Chilean dolphin C. eutropia 

 

Chilean dolphin, Cephalorhynchus eutropia

Genus: Cephalorhynchus

The dolphins of the genus Cephalorhynchus belong to the Mammalian Order Cetacea, in the suborder Odontoceti.  All toothed whales belong to the suborder Odontoceti, which is Latin for "toothed whales".  These dolphins belong to the oceanic dolphin family, Delphinidae.  Other members of this family include the killer whale, long-beaked common dolphin, and pilot whale.  The generic name, Cephalorhynchus, is from the Greek kephale, which means "head", and rhunkhos, which means "snout".  This refers to the gradual slope from the head to the snout, which lacks a defined melon and beak.  These dolphins are considerably smaller than most other oceanic dolphin species and have a very recognizable blunt dorsal fin.

Chilean dolphin, Cephalorhynchus eutropia

Southern dolphins are generally darker shades of black or gray on their face, pectoral fins, dorsal fin and flukes.  Commerson's dolphin has the most extreme contrast, with a white body.  Other species are predominantly gray.  Adults of all species range from 3.5-5 feet in length.  These dolphins weigh between 60-190lbs.  Males are generally larger than females.

Groups of 1-5 individuals are commonly observed in shallow, murkier waters.  The Chilean dolphin occasionally enters river systems.  Crustaceans, squid and small fish are often taken in these shallow waters.  Their habitat and lifestyle is very similar to that of members of Phocoenidae, which occupy coastal waters of the Northern Hemisphere.  Females give birth during the spring and summer months.  Gestation lasts about 12 months.  Newborn calves are 1.5-2 feet in length, weighing about 10-17lbs.  Sexual maturity is attained at 5-9 years.  Lifespan is estimated at 20 years.

Commerson's dolphin Cephalorhynchus commersoni

The specific name, commersoni, is named for Dr. Philibert Commerson (1727-1773), a French naturalist aboard an expedition with French navigator Louis Antoine de Bougainville during the 1760's.  Commerson first described these dolphins in 1767.  Commerson's dolphin is native to the coastal waters of southeastern South America, including Argentina, Tierra del Fuego, Falkland Islands, Kerguelen Islands and possibly even more southern islands including South Georgia and South Shetland.

Commerson's dolphin, Cephalorhynchus commersoni

Chilean dolphin Cephalorhynchus eutropia

The specific name, eutropia, is derived from the Greek words eu, meaning “well or good”, and tropis, meaning "keel".  This may refer to the shape of the skull, which has a keel-like ridge.  Chilean dolphins inhabit the coastal waters of southwestern South America, including Chile and Tierra del Fuego.

Chilean dolphin, Cephalorhynchus eutropia

Heaviside's dolphin Cephalorhynchus heavisidii

The specific name, heavisidii, is named for Captain Haviside, the first to describe the dolphin in 1827.  However, the captain's name was misspelled, and the species is now commonly called "Heaviside's" dolphin.  Heaviside's dolphin is native to the coastal waters of southwestern Africa.

Hector's dolphin Cephalorhynchus hectori

The specific name, hectori, is named for James Hector (1834-1907), a curator of the Wellington Museum in New Zealand.  Hector's dolphin is native to the coastal waters of New Zealand.

Conservation

Coastal fishermen occasionally capture individuals for bait or accidentally drown dolphins in their fishing gear.  All species are threatened by local fishermen.  Fortunately, the threats of fishermen have been recognized and no members of this genus are in immediate threat of extinction.

 

Content provided by Canisius College students under the direction of Michael Noonan, PhD.