The false killer whale (Pseudorca crassidens) is a large toothed whale that lives in the tropical and sub-tropical open ocean. They occur in the tropics and subtropics of the Pacific Ocean, and are best studied in the waters around Hawaii and New Zealand.
In Hawaiian waters there are three populations: an offshore (pelagic) population, a Northwestern Hawaiian Islands population, and a small population associated with the main Hawaiian Islands – this latter population are long-term residents, they are kama‘aina, truely Hawaiian, Pseudorca. This population was listed as Endangered under the Endangered Species Act in November 2012. More is known about Pseudorca in Hawaiian waters than anywhere else in the world, and they are one of the highest priority species for Cascadia’s Hawai‘i research program.
Pseudorca are uncommon everywhere – they are at the top of the food web, and like other top predators they are naturally rare. A National Marine Fisheries Service (NMFS) study of all of Hawaiian waters out to the international boundary found that false killer whales were the least abundant of the 18 species of toothed whales and dolphins found in Hawaiian waters.
In Hawaiian waters Pseudorca regularly use near-shore areas. The island-associated population is genetically differentiated from Pseudorca in offshore Hawaiian waters (Chivers et al. 2007; Martien et al. 2011).
Photographs obtained by researcher Dan McSweeney (of the Wild Whale Research Foundation, based in Holualoa) from the mid-1980s and 1990s have been used to demonstrate that this population has long shown fidelity to the area (Baird et al. 2008). The most recent population estimate for the main Hawaiian Islands insular population is approximately 150 individuals.
Our photo-identification work has demonstrated that Pseudorca have long-term bonds. They share their prey, not only with their companions, but also with humans. A Pseudorca that was alone in British Columbia and Washington from the late 1980s until a few years ago, far from their normal range off Mexico, repeatedly caught large salmon and would offer them to boaters. In Hawaiian waters, Pseudorca have offered fish to human snorklers and divers.
Like the killer whale (not particularly closely related but with a very similar skull), Pseudorca are long-lived (into their 60s), slow to reproduce (having one calf only every 6 or 7 years), and do not start reproducing until their teens. Like humans, females go through menopause, and have a long post-reproductive period. Thus Pseudorca populations would be very slow to recover from any impacts from human activities. Also like killer whales, because they are long-lived upper-trophic level predators, they accumulate high levels of toxins and may be impacted by competition with human fisheries.
Recent evidence indicates the insular population of Pseudorca in Hawai‘i has declined dramatically over the last 20 years (Reeves et al. 2009). Five years of aerial surveys undertaken from 1993 through 2003 by Joe Mobley of the University of Hawai‘i West O‘ahu have shown a steep decline in sighting rates. Group sizes of the largest groups documented in surveys undertaken by Steve Leatherwood and Randy Reeves in 1989 were almost four times larger than the entire current population estimate (Reeves et al. 2009).
Pseudorca are closely related to, and often confused with pygmy killer whales, short-finned pilot whales and melon-headed whales, all of which are also found in Hawaiian waters.