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New observations and a review of killer whale (Orcinus orca) sightings in Papua New Guinea waters
Abstract: Although typically considered a temperate to cold water species, killer whales (or orca) (Orcinus orca) have been reported intermittently in tropical waters. While the IUCN (IUCN, 2000) does not list the species as present in Papua New Guinea waters, the records presented here indicate it is found in the area for at least 10 months of the year. A total of 94 sightings of killer whales in Papua New Guinea waters were complied. Thirty-seven sightings from April 1987 to July 2002 were recorded with an exact date and location, with a further 57 sightings of unknown date or exact location. Twenty-seven of all records had either photographs or videotape to confirm species identification. The earliest reference to killer whales in this region was from 1956, when they were recorded taking fish off long-lines. Killer whales from Papua New Guinea waters have been observed feeding on four species of elasmobranchs (scalloped-hammerhead shark, Sphyrna lewini; grey reef shark, Carcharhinus amblyrhynchos; manta ray, Manta birostris; and blue-spotted ray Dasyatis kuhlii) and four species of fin-fish (yellow-fin tuna, Thunnus albacares; big-eye tuna, Thunnus obesus; Indo-Pacific sailfish, Istiophorus platypterus; and sunfish, Mola mola). These are the first records, worldwide, of killer whales feeding on scalloped-hammerhead sharks, grey reef sharks and blue-spotted rays. Killer whales in these waters have been reported in association with two species of cetaceans (sperm whales, Physeter macrocephalus and spinner dolphins, Stenella longirostris). Photo-identification images were collected for 14 individuals and a catalogue established. Matches were made for two animals—a female sighted approximately 30 n mi and two days apart and a sub-adult male sighted in the same region 16 months apart. Some individual killer whales from these waters have been observed with grey under-flukes, in contrast to white, which is typically described for this species.
Key Words: KILLER WHALE; ORCINUS ORCA; PAPUA NEW GUINEA; PHOTO-IDENTIFICATION; FORAGING; ELASMOBRANCHES; FIN-FISH
Document Type: Research article