Abstract: On 21 December 1998, four killer whales (an adult male, two females or immature males, and one juvenile) attacked a group of sevengill sharks (Notorhynchus cepedianus) off the coast of Caleta Malaspina, Chubut, Argentina. Persecution, catches, and tossing behavior were performed by the two females or immature males in the inlet. Next day, carcasses of several sharks were found on the beach adjacent to the attack area. Seven of them were intact and sized approximately 2.5 m in length. The presence of complete sevengill shark carcasses on the beach suggests that they were attempting to avoid capture by the killer whales by stranding on the beach. Attacks on sevengills by killer whales in Caleta Malaspina are frequent in some years, especially from mid-December to mid-January when the sevengill seems to use the inlet as a nursery ground. The observation of the same male feeding both on pinnipeds in Peninsula Valdes and on sharks in Caleta Malaspina may indicate that at least some groups in the Southwestern Atlantic could regularly feed on both fish and marine mammals. This is the first report of an attack of killer whales on sharks off the coast of Patagonia, and the first report of tossing behavior in sharks.

Key Words: Killer whale, Orcinus orca, attack, tossing behavior, sevengill shark, Patagonia, Argentina

Document Type: Research article

DOI: 10.1578/AM.30.3.2004.376

Page Numbers: 376-379

$12.00 each Vol. 30, Iss. 3, Reyes_Garcia-Borboroglu