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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 |
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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.
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