Pilot whales are cetaceans belonging to the genus Globicephala. The two extant species are the long-finned pilot whale (G. melas) and the short-finned pilot whale (G. macrorhynchus). The two are not readily distinguishable at sea, and analysis of the skulls is the best way to distinguish between the species. Between the two species, they range nearly worldwide, with long-finned pilot whales living in colder waters and short-finned pilot whales living in tropical and subtropical waters. Pilot whales are among the largest of the oceanic dolphins, exceeded in size only by the orca. They and other large members of the dolphin family are also known as blackfish. Pilot whales feed primarily on squid, but will also hunt large demersal fish such as cod and turbot. They are highly social and may remain with their birth pod throughout their lifetime. Short-finned pilot whales are one of the few non-primate mammal species in which females go through menopause, and postreproductive females continue to contribute to their pod. Pilot whales are notorious for stranding themselves on beaches, but the reason behind this is not fully understood. Marine biologists have shed some light on the matter, suggesting that it is due to the mammals inner ear (their principal navigational sonar) being damaged from noise pollution in the ocean, such as from cargo ships or military exercises. The conservation status of short-finned and long-finned pilot whales has been determined to be least concern.
Naming The animals were named "pilot whales" because pods were believed to be "piloted" by a leader. They are also called "pothead whales" and "blackfish". The genus name is a combination of the Latin word globus ("round ball" or "globe") and the Greek word Kephale ("head").
Taxonomy and evolution
Pilot whales are classified into two species; the long-finned pilot whale (Globicephala melas) and the short-finned pilot whale (G. macrorhynchus). The short-finned pilot whale was described, from skeletal materials only, by John Edward Gray in 1846. He presumed from the skeleton that the whale had a large beak. The long-finned pilot whale was first classified by Thomas Stewart Traill in 1809 as Delphinus melas. Its scientific name was eventually changed to Globicephala melaena. Since 1986, the specific name of the long-finned pilot whale was changed to its original form melas. Other species classifications have been proposed but only two have been accepted. There exist geographic forms of short-finned pilot whales off the east coast of Japan, which comprise genetically isolated stocks. Fossils of an extinct relative, Globicephala baereckeii, have been found in Pleistocene deposits in Florida. Another Globicephala dolphin was discovered in Pliocene strata in Tuscany, Italy, and was named G. etruriae. Evolution of Tappanaga, the endemic, larger form of short-finned pilots found in northern Japan, with similar characteristics to the whales found along Vancouver Island and northern United States coasts, has indicated that the geniture of this form could be caused by the extinction of long-finned pilots in north Pacific in the 12th century, where Magondou, the smaller, southern type possibly filled the former niches of long-finned pilots, adapting and colonizing into colder waters.
Description
Pilot whales are mostly dark grey, brown, or black, but have some light areas such as a grey saddle patch behind the dorsal fin. Other light areas are an anchor-shaped patch under the chin, a faint blaze marking behind the eye, a large marking on the belly, and a genital patch. The dorsal fin is set forward on the back and sweeps backwards. A pilot whale is more robust than most dolphins and has a distinctive large, bulbous melon. Pilot whales' long, sickle-shaped flippers and tail stocks are flattened from side to side. Male long-finned pilot whales develop more circular melons than females, although this does not seem to be the case for short-finned pilot whales off the Pacific coast of Japan.
Long-finned and short-finned pilot whales are so similar, it is difficult to tell the two species apart. They were traditionally differentiated by the length of the pectoral flippers relative to total body length and the number of teeth. The long-finned pilot whale was thought to have 9–12 teeth in each row and flippers one-fifth of total body length, compared to the short-finned pilot whale with its 7–9 teeth in each row and flippers one-sixth of total body length. Studies of whales in the Atlantic showed much overlap in these characteristics between the species, making them clines instead of distinctive features. Thus, biologists have since used skull differences to distinguish the two species. The size and weight depend on the species, as long-finned pilot whales are generally larger than short-finned pilot whales. Their lifespans are about 45 years in males and 60 years in females for both species. Both species exhibit sexual dimorphism. Adult long-finned pilot whales reach a body length of approximately 6.5 m, with males being 1 m longer than females. Their body mass reaches up to 1,300 kg in females and up to 2,300 kg in males. For short-finned pilot whales, adult females reach a body length of about 5.5 m, while males reach 7.2 m and may weigh up to 3,200 kg.
Distribution and habitat
… excerpt ends here. Continue reading the full article.
