Long-finned pilot whale

 

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Classification:

Global Population

Description and Natural History

Physical Description
The long-finned pilot whale is a medium-sized whale, with an elongated body, a bulbous forehead and a short, almost imperceptible beak. In mature males, the rounded forehead overhangs the snout. The mouth-line is curved upwards, and the crescentric blowhole is set slightly to the left of centre on the top of the head.

The dorsal fin is prominent and falcate, with a low profile, and long base and is located relatively far forward on the back (about a third of the way back from the head). In adult males, the dorsal fin may have a thicker leading edge and rounder form than in females. Flippers are very long and slender, with pointed tips and an angled leading edge forming an ‘elbow’. The tail stock has a thick keel. Tail flukes are pointed at the tips with a concave trailing edge and a deep median notch.

Pilot whales are almost completely black in colour. New-born and immature animals may be slightly lighter in colour, and younger whales are often slightly spotted with grey. Most adults have scars, ranging from squid sucker marks to tooth scars caused by interactions with conspecifics. Individual variation in the colouration of pilot whales is known to occur; adults generally have light markings on the throat and belly and sometimes behind the dorsal fin and eye, typically a long anchor-shaped ventral patch, dorsal saddle and eye blaze are noted. The grey dorsal saddle is found just behind the dorsal fin and can measure more than 1 m in length, tapering to a point towards the tail. The eye blaze is a narrow, elongated patch up to 20 cm long behind the eye. The dorsal fin saddles and eye blaze are not as distinctive in animals from the North Atlantic as those found in the Southern Hemisphere. These colour patterns are not very useful for individual identification, due to the fact that they are often indistinct and difficult to see in the field.

The number of teeth is variable but there are usually 9 to 12 in each row (around 40 total). The teeth are sharp and pointed, but may become worn with age.

Natural History 
Pilot whales are extremely social. Pods of pilot whales range in size from less than ten to more than 1,000 individuals, although they are generally found in groups of 20 to 100 animals. Herds observed in the open ocean tend to be smaller than the herds of animals stranded or driven ashore, and herd size is thought to vary depending on various circumstances such as feeding, environmental stress and migrations. At times, smaller units may aggregate to form temporary larger groups, as has been demonstrated in other social cetacean species during seasonal movements, foraging, and breeding activities.

Long-finned pilot whales occur in some temperate and sub-polar oceans, and are usually found in deep, offshore waters, although they may be seen in coastal waters in parts of the North Atlantic Ocean. The long-finned pilot whales in the Southern Hemisphere are isolated from those in the Northern Hemisphere.
 
Long-finned pilot whales are often found along the edge of continental shelves, since they prefer deep water. The US east coast continental shelf-edge has been identified as a high use cetacean habitat, and surveys have shown that pilot whales are a principal species of the cetacean assemblage in those waters. Generally, the shelf edge is an area of increased bottom relief and this has been shown to influence the distribution of pilot whales. They are usually associated with the steepest bottom topography.

Female long-finned pilot whales live longer than males, and may live for 60 years or more. Males generally have a life span of around 50 years. Pilot whales tend to strand, both individually and in entire herds of up to several hundred animals. This may be the most serious natural mortality factor.

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Status of the Species

Status 
An estimate of the overall abundance of long-finned pilot whales from the North Atlantic and Southern Ocean numbers at least in the hundreds of thousands. Sightings surveys in the Atlantic in the late 1980’s provided a population estimate of about 750,000 pilot whales in the north-eastern North Atlantic.

Threats to the Species 
There is a long history of exploitation of long-finned pilot whales in the Northern Hemisphere. In the eastern Atlantic, the main exploitation has been in the Faroes, where a drive fishery with an annual catch of several thousand has persisted for several hundred years. Small numbers have also been hunted in Norway, West Greenland and Iceland, and previously in northern Scotland. In the western Atlantic, the principal hunt was in Newfoundland between 1947 and 1964, with catches peaking at 10,000 in 1956. From the mid 1700’s to 1920’s, a drive fishery was very active at Cape Cod. There has also been a substantial bycatch of pilot whales, for example, in the mackerel fishery off the north-eastern United States, and off south-west England, and in trawl and gill nets elsewhere in the North Atlantic and Mediterranean.

The Faroese hunt has been the subject of much concern and controversy in recent years. Concerns have focused on the inhumane methods used in the hunt and the question of whether the hunt is necessary (and therefore still justified) from a socio-economic or nutritional point of view. Indeed, it has been suggested that the meat of the pilot whales may be posing a significant health risk to those who consume it due to the high levels of pollutants within it, particularly metals such as mercury and cadmium and PCBs and other organochlorines.

Pilot whales stranded around the British Isles have been examined for organochlorine residues in blubber and liver tissues. High, possibly age-related, accumulated levels of PCB, DDT residue and dieldrin were found which were within the range of levels published for other cetaceans. PCB levels were, however, higher than any others previously published for long-finned pilot whales. Levels of organochlorine contaminants are cumulative with age in males, but show a decrease in sexually mature females, suggesting a transfer from the mother to the offspring during gestation and lactation. This has been demonstrated in bottlenose dolphins. Levels of mercury and cadmium were also detected in the liver of pilot whale foetuses showing that a transplacental transfer of these elements occurs. Cadmium is also transferred to calves by lactation.

There are also concerns regarding the effects that underwater noise pollution may have upon marine mammals. In the Mediterranean, long-finned pilot whale vocalisations were studied at a time when active military sonar was being broadcast. Vocalisations were found to alter in response to the noise, which dominated the acoustic environment over a significant range. The significance of such changes to cetacean vocalisations and its underwater habitat are unknown.

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Authors and Sources

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