Atlantic humpback 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 humpback dolphin. Coloration is also somewhat variable. Animals are typically slate gray on the sides and back, and light gray below. Some individuals have dark spots or flecks on the tail stock. Tooth counts are 27-31 per upper tooth row, and 26-30 per lower row. Adults are up to about 2.8 m in length, and weigh up to 284 kg.
Can be Confused With
The similar-looking bottlenose dolphin also inhabits the inshore range of the Atlantic humpback dolphin. The two can be distinguished by differences in beak length, dorsal fin shape (including the presence of the hump in Sousa), and coloration.
Atlantic humpback dolphins’ range include tropical to subtropical West Africa (from Morocco south to at least northern Angola). They apparently occur as distinct populations, separated by areas of low or zero density. They are found primarily in estuarine and coastal waters. Some humpback dolphins may occupy rivers, such as the Niger, but it is not thought that there are separate freshwater populations.
Ecology and Behavior
Atlantic humpback dolphins inhabit estuarine and coastal waters. Groups of Atlantic humpback dolphins generally contain 5-7 individuals, occasionally up to 25 animals. Groups often feed very near shore. These animals generally do not bowride. Little else is known of the behavior of these animals.
Breeding has been documented in March and April, but the breeding season may well be more protracted. Length at birth is thought to be about 1 m.
Feeding and Prey
Atlantic humpback dolphins feed on schooling fishes and, contrary to some descriptions, are not thought to eat vegetable matter. Off the coast of Mauritania, fishermen cooperate with Atlantic humpback and bottlenose dolphins to capture mullet with beach seines.
Threats and Status
Major threats include:
• Incidental catches in fishing nets
• Takes by local people in West Africa
• Habitat destruction
• Vessel collisions
• Environmental contamination
This species has a very restricted range, and is considered to be threatened on a global scale. However, limited information makes the current conservation status of Atlantic humpback dolphins “Data Deficient” (IUCN) and “Not Listed&rdquo (ESA).
Maigret, J. 1980. Donnees nouvelles sur l'ecologie du Sousa teuszii (Cetacea, Delphinidae) de la cote ouest africaine. Bulletin de l'Institut Francais d'Afrique Noire 42A:619-633.
Ross, G.J.B. 2002. Humpback dolphins Sousa chinensis, S. plumbea and S. teuszii. pp. 585-589 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Ross, G.J.B., G.E. Heinsohn, and V.G. Cockcroft. 1994. Humpback dolphins Sousa chinensis (Osbeck, 1765), Sousa plumbea (G. Cuvier, 1829) and Sousa teuszii (Kukenthal, 1892). pp. 23-42 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Volume 5: The first book of dolphins. Academic Press.
Van Waerebeek, K., L. Barnett, A. Camara, A. Cham, M. Diallo, A. Djiba, A.O. Jallow, E. Ndiaye and O.S. Ould
Bilal. 2002. Status and biology of the Atlantic humpback dolphin Sousa teuszii (Kükenthal, 1892) (SC/
54/SM9). Paper presented to the Scientific Committee at the 54th Meeting of the International Whaling
Commission, April 26-May 10, Shimonoseki, Japan.