Abstract: Very little is known about the foraging ecology of killer whales (Orcinus orca) in tropical oceans and on how these large apex predators affect prey communities. In most tropical waters, the presence of killer whales is unpredictable, and most information on their ecology is inferred from opportunistic records. This is particularly the case in the Indian Ocean where limited information is available. Between 2002 and 2017, killer whales were opportunistically encountered around the Mozambique Channel island of Mayotte in the eastern Comoros Archipelago (southwest Indian Ocean). A total of 15 killer whale sightings collected by various local experts were compiled and used to describe observed feeding events. Twenty-seven distinct individuals from four separate groups were identified by photo-identification, highlighting short-term site fidelity (minimum 7 days) to this area. Feeding was observed on seven occasions, and recorded prey included two species of elasmobranchs (Centroscymnus coelolepi and Mobula spp.) and two species of cetaceans: a humpback whale (Megaptera novaeangliae) calf and a pantropical spotted dolphin (Stenella attenuata). This study represents the first account of killer whales foraging on a combination of marine mammals and elasmobranchs in tropical waters, and describes the first presumed predation on a humpback whale calf in the southwest Indian Ocean.
Key Words: killer whale, Orcinus orca, Indian Ocean, elasmobranchs, humpback whale, Megaptera novaeangliae, pantropical spotted dolphin, Stenella attenuata, feeding ecology, tropical ecosystems
Page Numbers: 196-205
Observations of Killer Whale (Orcinus orca) Feeding Behavior in the Tropical Waters of the Northern Mozambique Channel Island of Mayotte, Southwest Indian Ocean