The False Killer Whale, Pseudorca crassidens, is a large, highly social oceanic dolphin. It has a slim, entirely black or dark gray body and is the third largest member of the oceanic dolphin family, Delphinidae, with adult males reaching up to six meters in length. Its common name comes from the fact that its skull structure is similar to that of the Orca (Orcinus orca), though the species do not resemble each other externally. While the False Killer Whale is widespread globally, its distribution is characterized by a preference for specific warm-water habitats.
Global Distribution and Preferred Waters
False Killer Whales are cosmopolitan, found throughout the world’s oceans, but their distribution is not even. They are primarily concentrated in tropical and warm temperate zones, generally not ranging poleward beyond 50 degrees latitude in either hemisphere.
This preference means the species is present in all three major ocean basins: the Atlantic, Pacific, and Indian Oceans. In the Pacific, their range extends from Japan to the Eastern Tropical Pacific and south to New Zealand. In the Atlantic, they are routinely sighted in the warm Gulf Stream waters off the East Coast of the United States and within the Gulf of Mexico.
Their presence in warm temperate regions sometimes correlates with warmer oceanographic events, occasionally pushing their range further north or south, such as sightings near British Columbia or Argentina. However, these high-latitude occurrences are often temporary, with the core population residing in consistently warmer waters closer to the equator.
Distinctive Localized Populations
Although the False Killer Whale has a vast global range, its population structure includes specific, often genetically distinct, localized groups. These groups, sometimes called stocks, exhibit site fidelity and concentrate around oceanic islands or continental shelf edges. The most studied populations are found near the Hawaiian Islands, where three separate stocks have been identified.
The endangered Main Hawaiian Islands Insular stock remains close to the main islands’ shores. This genetically isolated population is estimated to number fewer than 200 individuals. A second group is the Northwestern Hawaiian Islands population, which associates with the remote islands and atolls of that region.
The third Hawaiian stock is the Pelagic population, which ranges widely across the larger Hawaiian Exclusive Economic Zone (EEZ) and beyond. This offshore group is genetically distinct from the near-shore insular stock. Other localized groups include established populations in the northern Gulf of Mexico and off the coast of Japan. Genetic evidence also suggests a distinct coastal population exists in the waters of northern Australia.
Deep-Water Habitat Requirements
False Killer Whales predominantly inhabit the pelagic zone, the open ocean far from land and continental shelves. Their preferred environment is deep water, typically at least 1,000 meters, with sightings most frequent where depth exceeds 3,000 meters.
This preference for the deep, oceanic environment is linked to their foraging behavior. They are active predators that primarily target large, deep-dwelling fish and squid, such as tuna, mahi-mahi, and swordfish. These prey items are generally found in greater abundance in deep-sea habitats.
Although they prefer the open ocean, some localized populations, like those in Hawaii, may be found closer to shore due to unique oceanographic conditions. Island environments can create upwelling that concentrates their deep-water prey near landmasses. The critical habitat for the Main Hawaiian Islands insular population is defined as the waters surrounding the islands from the 45-meter depth contour out to the 3,200-meter depth contour.