False killer whale - Pseudorca crassidens

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The false killer whale is one of several species of delphinids that fishermen sometimes call blackfish. It is a large, dark gray to black dolphin, with a faint light gray patch on the chest, and sometimes light gray areas on the head. It has a long slender body, a rounded overhanging forehead, and lacks a beak. The dorsal fin, although variable in shape, tends to be falcate and slender, and is generally rounded at the tip. The flippers have a characteristic hump on the leading edge, probably the species’ most diagnostic character.

Each jaw contains 7-12 pairs of large conical teeth, which are round in cross-section. Adults are up to 6 m (males) or 5 m (females) long; newborns are 1.5-2.1 m. Large males may weigh up to 2,000 kg. Skulls of false killer whales from Australia, South Africa, and Scotland have been shown to differ, and this suggests the existence of different populations in these areas.

False killer whales are most commonly confused with pygmy killer and melon-headed whales, and less commonly, pilot whales. Shape of the head, dorsal fin, and flippers will be the best characters to use in distinguishing them (the flipper hump of false killer whales is diagnostic).

False killer whales are found in tropical to warm temperate zones, generally in relatively deep, offshore waters of all three major oceans. They do not generally range poleward of about 50° in either hemisphere. However, some animals may move into shallow and more high-latitude waters, on occasion.

As is the case for most of the tropical oceanic delphinids, this species is poorly-known. In some areas, false killer whales take fish from longlines and thus earn the ire of fishermen. Groups of 10-60 are typical, though much larger groups are known. This is one of the most common species involved in cetacean mass strandings. The false killer whale is a lively, fast-swimming cetacean, which behaves more like the sprightly smaller dolphins than other mid-sized cetaceans. No seasonality in breeding is known for the false killer whale.

False killer whales have a broad diet characterized by: Squid > fish. Although false killer whales eat primarily fish and cephalopods, they also have been known to attack small cetaceans and, on one occasion, even a humpback whale. They feed by seizing their prey.

Known prey species include:

Fish: Oncorhynchus sp., Sarda sp., Coryphaena sp., Thunnus albacares, Psuedosciana sp., Lateolabrax japonicus, Seriola lalandi, Tachysurus spp., Macruronus magellanicus, Micropogonias furnieri, Pogonias cromis, Genypterus blacodes

Invertebrates: Ommastrephes bartramii, Martialia hyadesi, Illex argentinus, Todarodes filippovae, Ocythoe sp., Moroteuthis ingens, Teuthowenia megalops, Octopoteuthis sp., Gonatus antarcticus, Mastigoteuthis sp., Lycoteuthis cf. diadema, Thysanoteuthis rhombus, Todarodes angolensis, Loligo v. reynaudii

Main threats include:

• Intentional kills by fishermen

• Harvest

• Fisheries bycatch

Neither the IUCN nor the United States government lists the false killer whale as threatened or endangered. False killer whales have a propensity for taking fish from longlines, thus earning them the ire of fishermen. Because of this habit, they have been shot and otherwise persecuted. In Japan, they have been targets of drive fisheries, largely because of perceived competition with fishermen for yellowtail. Incidental catches in fishing gear, such as driftnets and purse seines occurs at least occasionally. Live captures and damaging effects from pollutants are among the other potential threats to this species. The United States National Marine Fisheries Service estimates the Northern Gulf of Mexico stock to be 381 (CV = 0.62) and the Hawaiian stock to be 121 (CV = 0.47).

• iOBIS
• World Register of Marine Species (WoRMS)
• Encyclopedia of Life
• Catalog of Life
• Integrated Taxonomic Information System (ITIS)
• Barcode of Life

Alonso, M.K., S.N. Pedraza, A.C.M. Schiavini, R.N.P. Goodall and E.A. Crespo. 1999. Stomach contents of false killer whales (Pseudorca crassidens) stranded on the coasts of Strait of Magellan, Tierra del Fuego. Marine Mammal Science 15(3) 712-724.

Baird, R.W. 2002. False killer whale Pseudorca crassidens. pp. 411-412 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.

Hansen, L.J., K.D. Mullin and C.L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of Mexico from vessel surveys. U.S. Department of Commerce, SEFSC, Contribution No. MIA-94/95-25.

Kitchener, D.J., G.J.B. Ross and N. Caputi. 1990. Variation in skull and external morphology in the false killer whale, Pseudorca crassidens, from Australia, Scotland and South Africa. Mammalia 54:120-135.

Leatherwood, S., D. McDonald, R.W. Baird and M.D. Scott. 1989. The false killer whale, Pseudorca crassidens (Owen, 1846) a summary of information available through 1988. Ocean Unlimited Technical Report 89-001.

Mobley, J.R., Jr., S.S. Spitz, K.A. Forney, R.A. Grotefendt and P.H. Forestall. 2000. Distribution and abundance of odontocete species in Hawaiian waters preliminary results of 1993-1998 aerial surveys. U.S. Department of Commerce, SWFSC Administrative Report LJ-00-14C.

Odell, D.K. and K.M. McClune. 1999. False killer whale Pseudorca crassidens (Owen, 1846). pp. 213-244 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 6: The second book of dolphins and the porpoises. Academic Press.

Stacey, P.J., S. Leatherwood and R.W. Baird. 1994. Pseudorca crassidens. Mammalian Species 456:1-6.