This species, whose scientific name is Pseudorca crassidens (pseudo = false, orca = Latin for cetacean, e.g. marine mammals: whales and dolphins; crassidens = ‘thick-tooth’) is actually a member of the dolphin family, and is the only member of its genus. It was first described in 1846 and is the fourth largest dolphin in the world. The species is fairly widespread in its distribution; they have been observed in shallow water including the Mediterranean and Red Seas but are more common in the deeper tropical to temperate waters of the Atlantic, Pacific, and Indian Oceans. They are considered uncommon but there are no global population estimates. The United State (U.S.) National Marine Fisheries Service (NMFS) concluded that false killer whales were the least common of the 18 species of toothed whales and dolphins found in Hawaiian waters. Although not hunted commercially, they can be caught as bycatch and through other fishery interactions, such as the Hawaii longline fishery and bottomfish fishery off the Northwestern Hawaiian Islands. They are hunted in Indonesia, Japan, and the West Indies. In the US this species is listed as Endangered under the Endangered Species Act.
I first saw them this winter at Latitude 15N, 6 miles offshore of the Mexican coast of Oaxaca, when on board a boat operated by a local dive shop, emphasis on first saw, as with all my experiences on or under the sea, from Mexico to the Mediterranean to Vietnam, I had never seen them before. A large pod surrounded our boat so we were able to get as close as six feet. They are roughly 1/3 the size of killer whales, lack the white marks on the body, and have a similar shaped hook-like dorsal fin, but a blunt-shaped beak. At first I did not think they were dolphins, being used to seeing the narrow snout or beak of the bottlenose and other species. They are dark in color. Males are larger than the females at almost 20 feet (6 m), while females reach lengths of 15 feet (4.5 m). In adulthood, false killer whales can weigh approximately 1,500 pounds (700 kg).
Like killer whales and other toothed whales, they are predators and have been known to eat smaller dolphins. They feed during the day on fish and at night on cephalopods (octopus, cuttlefish). Other similarities include the production of few offspring, and slow maturation. Females reach sexual maturity around 10 years, males much later at 18 years. Breeding season lasts several months. Females ovulate once annually giving birth to a single calf following a 15-month gestation period, which is followed by lactation for one and a half to two years. They reproduce after approximately seven years. They are long-lived, to approximately 63 years.
They are social animals, and form strong bonds, so seeing a large group should not have been surprising. They are usually found in groups of ten to twenty that belong to much larger groups of up to 40 individuals. False killer whales are also found with other cetaceans, most notably bottlenose dolphins. To increase success of finding prey, these animals travel in broad swaths up to several miles wide. Sharing of food has been observed between individuals.
So keep your eyes open the next time you are on the lovely Pacific waters of the Oaxacan coast; you may be lucky enough to see these magnificent animals.