Killer whales ( Orcinus orca ) in Angolan and Gulf of Guinea waters, tropical West Africa

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Authors: Weir, Caroline R, Collins, Tim, Carvalho, Inês, Rosenbaum, Howard C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2010
• Subjects: Aquatic Science; Megaptera novaeangliae; Orca; Orcinus orca; Physeter macrocephalus
• Online Access: http://dx.doi.org/10.1017/s002531541000072x; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S002531541000072X

Killer whales Orcinus orca are considered to be relatively uncommon in tropical waters. Few sightings have been reported from the west coast of Africa due to a paucity of survey coverage. We present data on 32 killer sightings from tropical waters off Angola (N = 18), Gabon (N = 7), São Tomé (N = 6) and Cameroon (N = 1), comprising a combination of dedicated survey sightings (N = 21) and reliable anecdotal records ( n = 11). Killer whales were reported from coastal waters, the shelf edge and deep, oceanic areas. Sightings indicate a probable year-round occurrence of killer whales within the region. Mean group size was 5.6 animals. There was no difference in group size between sightings in waters >200 m deep and those on the continental shelf. No photo-identification matches were found between Angola, Gabon and São Tomé. Re-sightings of two individuals occurred annually in São Tomé during 2002–2004. Killer whales had external appearance consistent with the Type A nominate species form. Antagonistic encounters were recorded between killer whales and humpback whales Megaptera novaeangliae off Angola, Gabon and Cameroon, and with sperm whales Physeter macrocephalus off Angola. Predation on ocean sunfish Mola mola was recorded in São Tomé, and possible predation on sharks was recorded twice in Gabon.