Gray, 1846 - Short-finned pilot whale
Distinctive Characteristics
Pilot whales are large, with bulbous heads, dramatically upsloping mouthlines, and extremely short or non-existent beaks. The shape of the head varies significantly with age and sex, becoming more globose in adult males. The dorsal fin, which is situated only about one-third of the way back from the head, is low and falcate, with a very wide base (it also varies with age and sex). The flippers are long and sickle-shaped, 16 to 22% of the body length. Adult males are significantly larger than females, with large, sometimes squarish foreheads that may overhang the snout, strongly hooked dorsal fins with thickened leading edges, and deepened tail stocks with post-anal keels.
Except for a light grey, anchor-shaped patch on the chest, a grey “saddle” behind the dorsal fin, and a pair of roughly parallel bands high on the back that sometimes end as a light streak or teardrop above each eye, pilot whales are black to dark brownish grey. This is the reason for one of their other common names, blackfish (although the term blackfish is variously used, usually by fishermen, to refer to killer, false killer, pygmy killer, pilot, and melon-headed whales).
There are usually 7 to 9 short, sharply pointed teeth in the front of each tooth row.
Can be confused with In areas of overlap, the 2 pilot whales are difficult or impossible to distinguish at sea. Most sightings can be tentatively assigned to species, based on the area. Other smaller blackfish, such as false killer whales, and less commonly, pygmy killer and melon-headed whales, may be confused with pilot whales at a distance. Dorsal-fin shape is the best clue to distinguishing pilot whales from these species.
Size
Pilot whales are about 1.4 m long at birth. Adults reach 5.5 m (females) and 6.1 m (males). Males may weigh nearly 3600 kg.
Geographical Distribution
Short-finned pilot whales are found in warm temperate to tropical waters of the world, generally in deep offshore areas. They do not usually range north of 50°N or south of 40°S. There is some distributional overlap with their long-finned relatives (G. melas), which appear to prefer cold temperate waters of the North Atlantic, Southern Hemisphere, and previously the western North Pacific. Only short-finned pilot whales are thought to inhabit the North Pacific, although distribution and taxonomy of pilot whales in this area are still largely unresolved. There are 2 geographic forms of short-finned pilot whales off Japan.
Biology and Behaviour In the eastern Pacific, pilot whales are commonly associated with other species (such as bottlenose, Pacific white-sided, and Risso's dolphins, and sperm whales). Pods of up to several hundred short-finned pilot whales are seen, and members of this highly social species are almost never seen alone. Strong social bonds may partially explain why pilot whales are among the species of cetaceans that most frequently mass-strand. Although detailed studies of behaviour have only begun recently, pilot whales appear to live in relatively stable female-based groups.
Females become post-reproductive at around 35 years, but may continue to suckle young for up to 15 additional years, suggesting a complex social structure in which older females may give their own or related calves a “reproductive edge” through prolonged suckling. Calving peaks occur in spring and autumn in the Southern Hemisphere, and vary by stock in the Northern Hemisphere.
Although they also take fish, pilot whales are thought to be primarily adapted to feeding on squid. They show the tooth reduction typical of other squid-eating cetaceans.
Exploitation
Short-finned pilot whales have been hunted throughout their range in small numbers, although not as heavily as their congeners in the North Atlantic. The largest catches have recently occurred off Japan, where small coastal whaling stations and drive fisheries take a few hundred annually. A catch of a few hundred per year existed until recently in the Caribbean, but numbers taken there have apparently declined. Incidental catches in fishing gear are known for several areas. A few have also been captured live off southern California for display and research.
IUCN Status
Insufficiently known.