The Atlantic Humpback Dolphin is endemic to the eastern tropical Atlantic, where it is limited to coastal and inshore waters (Ross 2002, Van Waerebeek et al. 2004). It occurs in nearshore waters off tropical to subtropical West Africa, from Western Sahara south to at least southern Angola (Notarbartolo di Sciara et al. 1998, Van Waerebeek et al. 2004).
The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.
The validity of this species has been questioned in the past few years, but recent studies on skull morphology have made it apparent that the species is indeed valid and separate from the Indo-Pacific Humpback Dolphin (see Jefferson and Van Waerebeek 2004). Further studies on molecular genetics of the genus are underway and preliminary results support this conclusion (H. Rosenbaum pers. comm. to T. Jefferson 2006). The Atlantic Humpback Dolphin appears to be isolated from other humpback dolphins by a gap in distribution of at least 2,000 km on the southwestern coast of Africa, an area dominated by cold upwelling associated with the Benguela Current System (see Jefferson and Van Waerebeek 2004).
Atlantic Humpback Dolphins are found primarily in estuarine and shallow (< 20 m) coastal waters with soft sediment bottoms (Van Waerebeek et al. 2004). They have been observed as far as about 50 km up the Saloum River and are known to enter the Niger and Bandiala rivers, but they rarely travel far upstream and usually remain within the range of tidal influence (Van Waerebeek et al. 2004). There is no evidence to suggest the existence of separate freshwater subpopulations. In at least some areas (e.g., Gabon and Mauritania), these dolphins occur in the surf zone just offshore of the breakers (Busnel 1973; Tim Collins pers. comm. to T. Jefferson, 2007). There are no reports from offshore waters. Among the features that have been described as aspects of preferred habitat are proximity to sandbanks, brackish, mangrove-lined estuaries, and turbid waters with temperatures ranging between 17°C and 28°C (Maigret 1980, Ross et al. 1994).
There is little information on the diet of Atlantic humpback dolphins. They appear to feed on nearshore schooling fishes such as mullet (Mugil spp.) and, contrary to some descriptions, are not thought to eat vegetable matter (see Van Waerebeek et al. 2004). Stomach contents have included grunts (Pristipoma jubelini) and bongo fish (Ethmalosa fimbriata) (Van Waerebeek et al. 2004).