Hump-backed Dolphins
 

Common Name: Hump-backed Dolphins
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Sousa
Species: Two species:
Atlantic Hump-backed Dolphin Sousa teuszii
Indo-Pacific Hump-backed Dolphin Sousa chinensis



Taxonomy/Description

The hump-backed dolphins belong to the Mammalian Order Cetacea, in the suborder Odontoceti. All toothed whales belong to the suborder Odontoceti, which is Latin for "toothed whales". This dolphin belongs to the oceanic dolphin family, Delphinidae. Other members of this family include the killer whale, long-beaked common dolphin, and pilot whale. There are two species of hump-backed dolphins, the Atlantic hump-backed dolphin, Sousa teuszii, and the Indo-Pacific hump-backed dolphin, Sousa chinensis. Some cetacean researchers divide the Indo-Pacific hump-backed dolphin species into as many four separate species. The specific name of the Indo-Pacific hump-backed dolphin, chinensis, means “of China”, referring to the Canton River of China, the location in which the animal was first described. The Indo-Pacific hump-backed dolphin and the Atlantic hump-backed dolphin are very closely related. They are distinguished primarily by their geographic location.

Hump-backed dolphins are easily identified by their “double” dorsal fins. A hump is located on the back of the animal, with a dorsal fin atop of the hump. Both species of hump-backed dolphin are gray in color. However, young Indo-Pacific hump-backed dolphins are dark in color, lightening with age, while juvenile Atlantic hump-backed dolphins are light in color, darkening with age. Adults of both species may grow to lengths of about six feet. Humpbacked dolphins weigh between 175-300lbs.

Habitat/Diet

Hump-backed dolphins prefer tropical, shallow, coastal waters. The Atlantic hump-backed dolphin inhabits the northern and central coastal regions of Africa, while the Indo-Pacific hump-backed dolphin lives throughout southeast Africa, southern Asia, and Australia. These dolphins are occasionally observed in estuaries and rivers throughout their range. They feed on a variety of small freshwater and saltwater fish, including sardines and mullet. Crustaceans are also eaten.

 


 

Researchers separating the Indo-Pacific hump-backed dolphins into four species base their designations with range. The population of the southeast African coast is named Sousa plumbea, those of southern China are named Sousa chinensis, the Australian and Bornean coastal population is named Sousa borneensis, and those of the Persian Gulf are regarded as Sousa letiginosa. Although some would argue these are distinct species, new evidence suggests these groups are subspecies of the Indo-Pacific hump-backed dolphin at most.

Behavior/Reproduction

Hump-backed dolphins live in small groups of 2-10 individuals, but it is not uncommon to see even smaller groups consisting of a female and calf or solitary animals. Gestation is 11-12 months. Calving peaks in the summer but may occur year round. Newborns are about 3ft in length.

Conservation

The development of regions inhabited by hump-backed dolphins greatly impacts there welfare. The construction of dams especially disrupts river ecology. Entanglement in fishing gear is also a threat. The Atlantic hump-backed dolphin inhabits coastal areas of less developed nations, and is threatened by fishermen. Shark nets, which protect tourist beaches occasionally entangle and drown these shallow water dolphins. Other human activities endanger dolphins, such as pollution. The worldwide population is unknown.

 

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