(Kükenthal, 1892) - Atlantic hump-backed dolphin
Distinctive Characteristics
Atlantic hump-backed dolphins have a long, distinct beak, broad flippers with rounded tips, and a moderately deepened tail stock. The dorsal fin is variable in shape, but generally emerges from a wide hump or ridge on the animal's back. Although this species is poorly known, it is probably sexually dimorphic, like the Indo-Pacific hump-backed dolphin.
Coloration is also variable. Animals are slate grey on the sides and back, and light grey below.
Tooth counts are 27 to 31 per upper tooth row, and 26 to 30 per lower row.
Can be confused with
The bottlenose dolphin also inhabits the inshore range of the Atlantic hump-backed dolphin. The 2 can be distinguished by differences in beak length, dorsal-fin shape (including the hump), and coloration.
Size
Adults are up to about 2.8 m in length, and weigh up to 284 kg. Length at birth is thought to be about 1 m.
Geographical Distribution
Atlantic hump-backed dolphins occur off tropical to subtropical West Africa, from Mauritania south to at least Cameroon, possibly to northern Angola. They are found primarily in estuarine and coastal waters. Some hump-backed dolphins inhabit rivers, such as the Niger, but it is not known if there are separate freshwater populations.
Biology and Behaviour
Groups generally contain 5 to 7 individuals, occasionally up to 25 animals. Groups often feed very near shore. These animals generally do not bowride.
Breeding has been documented in March and April, but the breeding season may be more protracted.
Hump-backed dolphins feed on schooling fishes and, contrary to some descriptions, probably do not eat vegetable matter. Off the coast of Mauritania, fishermen using beach seines cooperate with Atlantic hump-backed and bottlenose dolphins to capture mullet.
Exploitation
Hump-backed dolphins are taken in beach seines and shark nets in Senegal. There is apparently also some direct capture of small cetaceans in West Africa for human consumption. Also of concern are the effects of offshore foreign fishing and mangrove destruction.
IUCN Status
Insufficiently known.