Long-finned pilot whale
|Long-finned pilot whale|
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The long-finned pilot whale (Globicephala melas) is a large species of oceanic dolphin. It shares the genus Globicephala with the short-finned pilot whale (Globicephala macrorhynchus). Long-finned pilot whales are known as such because of their unusually long pectoral fins.
- 1 Taxonomy and naming
- 2 Anatomy and morphology
- 3 Behavior and life history
- 4 Distribution and abundance
- 5 Conservation
- 6 References
- 7 External links
Taxonomy and naming
Pilot whales get their name from the belief that there was a "pilot" or lead individual in their groups. The name for the genus, Globicephala is derived from a combination of the Latin words globus ("globe") and kephale ("head"). The specific name, melas, is Greek for "black". This species has also earned the nickname of pothead whale in some places because the shape of its heads reminded early whalers of black cooking pots. Long-finned pilot whales are commonly referred to as blackfish, which is a named shared with several other large dolphin species including short-finned pilot whales, killer whales, false killer whales, pygmy killer whales, and melon-headed whales, .
This species was first classified in 1809 by a man named Thomas Stewart Traill and given the name Delphinus melas. However, this scientific name was changed later to Globicephala melaena. Then in 1986, the specific name for this species was reverted to its original form melas.
Anatomy and morphology
The sexes are dimorphic, with females reaching lengths of up to 5.8 meters and 1800 kg (1.8 long tons; 2.0 short tons), while males are significantly larger at up to 7.6 meters and 3,500 kg (3.5 long tons; 3.7 short tons).
Despite its common name, the long-finned pilot whale is actually a large species of dolphin. The same is true of orcas and several other small whales. It has a bulbous forehead and is black or dark grey in colour with light grey or white markings on the throat and belly regions. This light grey patch found on the throat of pilot whales forms the shape of an anchor. Some individuals have other distinct markings such as a light coloured area behind dorsal fin, known as a saddle patch, as well as an upwards sweeping stripe just behind the eye. The dorsal fin is thick and falcate in nature, and is located about a third of the way down the length of the animal. The common name of this species is a reference to the pilot whale's long, sickle-shaped pectoral fins that are 15 to 20 percent of its total body length. Being a toothed whale, pilot whales have a single blow hole.
It can be challenging to tell male and female in apart in the wild for many cetacean species. Long-finned pilot whales are no exception, though it was thought in the past that males had hooked dorsal fins while females did not. Recent research on fin shape has shown that this is not a predictable way to distinguish between the sexes. However, males are bigger in size and relative fin dimensions as well as other characteristics may still be discovered to allow for distinguishing the sex of at least certain age classes for free-ranging pilot whales.
The ranges of long-finned and short-finned pilot whales overlap in some areas of the world. As the difference between them is mainly distinguished by the length of the pectoral fins, it is extremely hard to tell the two species apart in these areas.
Behavior and life history
Long-finned pilot whales are a very social species. They are usually seen in groups, which range in size from a couple of individuals to aggregations of over a thousand. However, 20 to 150 individuals are more commonly observed. Studies have shown that this species often forms small long-term social units made up of around 8-12 individuals. Genetic investigations of the pilot whales driven ashore in the Faroese hunts have shown a relatedness amongst whales, suggesting a matrilineal structure within social units.
These groups have been observed socializing with common bottlenose dolphins, Atlantic white-sided dolphins and Risso's dolphins. Pilot whales mainly feed on cephalopods, though in certain regions fish may be more prominent in their diet. Northwestern Atlantic whales are thought to dine predominately on short-finned squid.
Long-finned pilot whales can often be seen lobtailing and spyhopping. Occasionally they may also breach. This species is notorious for mass strandings. During a specific time of year, approximately December to March, these whales beach themselves in high numbers along the coast of New Zealand. The reasons for stranding are not fully understood, but because pilot whales have strong social bonds, it is hypothesized that when one animal strands, the rest of the group may have the tendency to follow. These whales have also been observed babysitting calves that are not their own, with one study showing that many of those doing the babysitting are males.
Songs of long-finned pilot whales. The cracking noise is caused by echolocation.
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Long-finned pilot whales make many different kinds of sounds. In addition to squeaks, whistles, buzzes, and other calls likely used for communicative functions, they also produce rapid clicks that function as a type of bio sonar known as echolocation. This allows the whales to "see" in the murky, dark environments that they live in by listening to the nature of the echoes that return.
The whistles and pulsed calls that pilot whales make seem not to fall into distinct types, but rather can be arranged on a continuum. These calls are produced in a wide frequency range, which has been observed from less than 1 kHz to about 20 kHz.
Females reach sexual maturity at about 3.7 m (12 ft) and 6 to 7 years of age. Males need about twice as long to reach sexual maturity at about 4.6 m (15 ft) and 12 years of age.
There is evidence that some males may stay with their mothers after they reach sexual maturity. Mating is thought to occur when different groups meet up, and breeding within units is a rare occurrence.
Gestation lasts approximately 12 to 15 months and calving occurs once every 3 to 5 years. Calves are generally 1.8 m (5 ft 11 in) at birth, and weigh about 102 kg (225 lb). The calf nurses for up to 27 months, with some evidence for longer lactation and extensive mother calf bonds. Most calves are born in the summer, though some calving occurs throughout the year. It has been suggested that males may compete for mates with fights involving butting, biting, and ramming.
Distribution and abundance
Though long-finned pilot whales appear to be abundant, there have been no recent reliable estimates for the worldwide population, leading to their IUCN status of "Data Deficient." Conservative estimates for the population found off Newfoundland estimated around 13,000 individuals. Another study estimated a total of 780,000 animals in the North Atlantic, though this study includes both short and long-finned pilot whales as they are hard to distinguish at sea.
Long-finned pilot whales are found in the North Atlantic (Globicephala melas melas), as well as the Southern Hemisphere (Globicephala melas edwardii). Those in the north are wide-ranging and have been observed off the coast of the eastern U.S. and Canada, across the Atlantic in places such as the Azores and the Faroe Islands, as well as down the western coast of Europe all the way to the Strait of Gibraltar and North Africa. In the southern ocean, long-finned pilot whales are thought to range from 19–60° S, but are commonly seen in the Antarctic Convergence Zone and other areas, showing that they go as far as 68° S. This species has been observed near sea ice in the Antarctic.
Though there are only two recognized living subspecies, there was once a third that was found in the western North Pacific around Japan. These are thought to have died off sometime between the 8th and 12th century. This unnamed form was documented in historical literature and confirmed by the discovery of fossils in several locations of Japan, such as on Rebun Island and in Chiba Prefecture. Their biological niche after extinction has likely been refilled by short-finned pilot whales, who are currently present in parts of this region.
Current conservation status
The North Sea and Baltic Sea populations of the long-finned pilot whale are listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), since they have an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
The long-finned pilot whale is also covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS), the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU).
Whaling of this species in the Faroe Islands in the North Atlantic has been practiced since about the time of the first Norse settlements on the islands. The hunts, called grindadráp in Faroese, are mainly executed during the summer. They are non-commercial and organized on a community level. The hunters first surround the pilot whales with a wide semicircle of many boats. The boats then drive the pilot whales into a bay or to the bottom of a fjord. It is regulated by Faroese authorities but not by the International Whaling Commission, which does not regulate the hunts of small cetaceans. As of the end of November 2008 the chief medical officers of the Faroe Islands have recommended that pilot whales no longer be considered fit for human consumption because of the level of mercury in the whales.
Though the Faroe Islands are home to the only remaining large scale long-finned pilot whale hunts in the world, this species has also been hunted historically elsewhere. An industrial drive fishery was started in the Trinity Bay area of Newfoundland, Canada in 1947 by a Norwegian whaling captain. The catches increased every year until in 1956, there were approximately 10,000 pilot whales successfully captured and killed. This species was also historically hunted along the New England coastline.
Aside from the Faroe Islands, a few pilot whales are taken opportunistically in Greenland each year.
Long-finned pilot whales are economically important in the whale-watching industry of some areas of the world, especially in eastern Canada. Even though there are a number of other species of whales found in the Gulf of the St. Lawrence and around Newfoundland, pilots are one of the more common ones sighted inshore during the summer season. The tour vessels used in these regions are normally old converted fishing vessels or zodiacs. In these places, pilot whales provide valuable income for people living in rural fishing communities.
The effects of whale-watching on long-finned pilot whales have not been well studied.
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