Atlantic humpback dolphin
The physical characteristics of the Atlantic humpback dolphin are similar to those of the Indo-Pacific humpback dolphin in the western portion of its range only. The Atlantic humpback dolphin is slightly smaller, but has the same distinctive hump on which the small falcate or triangular dorsal fin rests. This hump becomes more conspicuous with age. It has a rounded melon and long slender beak, broad flippers with rounded tips, and flukes with a concave trailing edge. The Atlantic humpback dolphin has less variation in colouration than its Indo-Pacific cousin and is generally slate grey on the back and sides, fading to a pale grey on the belly. The beak and fin tend to get lighter with age. In poor conditions they may be confused with bottlenose dolphins, but observation of the unmistakable hump should be definitive.
There has been substantial debate as to the validity of this species however it is now accepted, from both morphological and genetic evidence, that this is a distinct species from the Indo-Pacific humpback dolphin (Sousa chinensis). The Atlantic humpback dolphin is known to engage in cooperative fishing with Mauritanian fishermen by driving fish towards the shore and into their nets. In other areas of West Africa however, this species is hunted.
The behaviour of the Atlantic humpback dolphin has not been well studied however it is thought in general to be similar to that of the Indo-Pacific species. They are not very acrobatic and are shy around boats, rarely bow-riding and sometimes actively avoid boats. A coastal dolphin, it is found off West Africa from Morocco to Angola and generally not found in water deeper than 25m, spending most of its time in the tidal zone.
Both intentional and non-intentional takes are serious threats to the Atlantic humpback dolphin and are thought to be unsustainable. As it is coastal in nature, the Atlantic humpback dolphin faces additional human-induced threats such as habitat destruction, entanglement in fishing nets and pollution. The consensus is that this species exists as distinct populations throughout its range and for this reason the magnitude of the threats it faces in certain areas are of great concern for the long-term conservation of the species. In 2008 the IUCN listed the Atlantic humpback dolphin as Vulnerable.