Globicephala melas
Globicephala melas
The long-finned pilot whale (Globicephala melas Traill, 1809) is a cetacean belonging to the Delphinidae family.
Systematics –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Subkingdom Eumetazoa,
Superphylum Deuterostomia,
Phylum Chordata,
Subphylum Vertebrata,
Superclass Tetrapoda,
Mammalia class,
Subclass Theria,
Infraclass Eutheria,
Order Cetacea,
Family Delphinidae,
Genus Globicephala,
G. melas species.
The term is basionym:
– Delphinus melas Traill, 1809.
The terms are synonyms:
– Delphinus deductor Scoresby, 1820;
– Delphinus globiceps Temminck, 1841;
– Delphinus grampus Gray, 1846;
– Delphinus grinda Lyngbye, 1824;
– Delphinus melaena (Traill, 1809);
– Delphinus melas Traill, 1809;
– Globicephala edwardii Smith, 1834;
– Globicephala melaena (Traill, 1809);
– Globicephala melas subsp. leucosagmaphora Tomilin, 1962;
– Globicephala meloena Paulus, 1960;
– Globicephalus affinis True, 1889;
– Globicephalus australis Gray, 1871;
– Globicephalus chilensis Philippi, 1896;
– Globicephalus chiliensis Phillipi, 1896;
– Globicephalus conductor Rapp, 1837;
– Globicephalus edwardsii Gray, 1866;
– Globicephalus indicus (Blyth, 1852);
– Globicephalus intermedius Gray, 1827;
– Globicephalus melas Flower, 1885
– Globiceps affinis Flower, 1884;
– Globiceps melas Flower, 1884;
– Globiocephalus affinis Gray, 1846;
– Globiocephalus chilensis Philippi, 1896;
– Globiocephalus incrassatus Gray, 1862;
– Globiocephalus indicus (Blyth, 1852);
– Globiocephalus melas Murie, 1874;
– Globiocephalus swineval Gray, 1846;
– Grampus affinis Gray, 1866;
– Phocaena edwardsii True, 1889;
– Phocaena globiceps A.Smith, 1834;
– Phocaena globiceps Lesson, 1827;
– Sphaerocephalus incrassatus Gray, 1864.
Within this species the following subspecies are recognised:
– Globicephala melas subsp. edwardii (A.Smith, 1834);
– Globicephala melas subsp. melas (Traill, 1809).
Geographic Distribution and Habitat –
Globicephala melas is a cetacean that lives in the temperate and subarctic zones of both hemispheres, in oceanic waters and in some coastal waters of the Atlantic, Pacific, Indian and Mediterranean Seas. They also formerly roamed the western North Pacific Ocean, where they appear to be absent today. There is a sub-Antarctic population in the Southern Hemisphere, reaching 68°S and appearing to be isolated from the northern population. Comprehensive estimates of the global population have not been made. The number of individuals has been estimated at 750,000 in the northeastern and central North Atlantic and 200,000 in the sub-Antarctic population and 31 in the western North Sea. For 2008, it was listed on the IUCN Red List as a worldwide data deficient species (DD) due to lack of information on its population size and spatial distribution, as well as its trends. Without However, assessments of local populations or management units, such as, for example, the case of pilot whale populations in the Mediterranean. It is expected that new assessments of the Mediterranean Sea will be made in future years.
This species has been extensively studied in the Mediterranean Sea. Its spatial distribution is mainly between the waters of Cabo de Palos and the Strait of Gibraltar. Its populations would number 3,000 to 4,000 individuals, gathered in clans. The clans of the Strait of Gibraltar are currently known, which would be composed of about 300 individuals and would be associated with the steeper waters of the Strait; the Seco de los Olivos-Monte Dibouti clan, associated with deep waters around 1000 meters, in the waters of Granada and AlmerÃa, and probably two clans in the waters of the Region of Murcia. A first clan, associated with the canyons of Cartagena and Garrucha, and another with the temperate waters of the Cabo de Gata-NÃjar natural park. Pilot whales can also be found in the area between Monaco, Italy and France, in the heart of the Pelagos Cetacean Sanctuary.
As far as the oceanic populations are concerned, as mentioned, they are found in the northern Atlantic (subspecies Globicephala melas melas) and in the southern hemisphere (subspecies Globicephala melas edwardii). Northern ones are wide-ranging and have been observed off the east coast of the United States and Canada, across the Atlantic to places such as the Azores and Faroe Islands, as well as along the western coast of Europe to the Strait of Gibraltar and North Africa.
In the Southern Ocean, these dolphins are thought to range from 19 to 60°S, but are commonly seen in Antarctica and other areas, showing they range up to 68°S. This species has been observed near sea ice in the ‘Antarctica.
Historically, although there are only two recognized living subspecies, there was once a third which was found in the western North Pacific around Japan. This species is thought to have become extinct between the 8th and 12th centuries. This unnamed form has been documented in historical literature and confirmed by the discovery of fossils at several locations in Japan, such as Rebun Island and Chiba Prefecture. Their biological niche after the extinction was probably filled by the long-finned pilot whales, now present in parts of this region.
Description –
Globicephala melas is a sexually dimorphic cetacean species, with females reaching lengths of up to 5.7 meters and 1,300 kg in weight, while males are significantly larger up to 6.7 meters and 2,300 kg in weight.
It has a bulbous forehead and is black or dark gray in color with light gray or white markings on the throat and belly regions. This light gray spot, found on the throat, is shaped like an anchor. Some individuals have other distinguishing markings such as a light-colored area behind the dorsal fin, known as a saddle patch, as well as a stripe that extends upward just behind the eye.
The dorsal fin is thick and sickle-shaped in nature and is about one-third the length of the animal. The pectoral fins are long and sickle-shaped, accounting for 18 to 27 percent of its total body length. Being a toothed species they have only one blowhole.
It can be difficult to distinguish male and female in the wild for many cetacean species. These dolphins are no exception, although males were previously thought to have hooked dorsal fins while females did not. Recent research on fin shape has shown that this is not a predictable way to distinguish the sexes. However, males are larger in size, and relative fin sizes and other characteristics can still be discovered to help distinguish between sex and age groups.
The distinction between the two subspecies is not easy, in the first place because the populations overlap in some areas of the world and then because the difference between them mainly occurs in the length of the pectoral fins and the number of teeth, which at first sight does not make easy to distinguish the two species in these areas.
Biology –
Globicephala melas is a very social cetacean. They are usually seen in groups, ranging in size from a couple of individuals to aggregations of over a thousand. However, 20 to 150 individuals are most commonly observed. Studies have shown that this species often forms small long-term social units consisting of around 8-12 individuals. Genetic investigations of specimens washed ashore during hunting in the Faroes have shown relatedness between individuals, suggesting a matrilineal structure within social units. This means that the cubs, females and possibly males as well, stay with their mothers for life.
Females reach sexual maturity at about 8 years of age, while males reach sexual maturity at about 12 years of age. Mating appears to occur at any time of the year, but peaks in late spring/early summer for both Northern and Southern Hemisphere populations. Mating is thought to occur when different groups meet, and breeding within units is a rare occurrence.
Gestation lasts about 12 to 16 months and delivery occurs once every 3-6 years. Puppies are usually 1.6-2.0m at birth and weigh around 75kg. Most young are born in the summer, although some deliveries occur throughout the year. As mentioned, there is evidence that some males may remain with their mothers after reaching sexual maturity.
Ecological role –
As mentioned, the Globicephala melas is a very social cetacean and some groups have been observed socializing with dolphins of other species, however they have occasionally been observed harassing, mobbing or chasing other cetacean species.
These dolphins have also been observed babysitting pups of other species, with one study showing that many of the babysitters are males.
In addition, pursuits of killer whales have been documented in several parts of the world, including Iceland and the Strait of Gibraltar. This is thought to be due to competition for prey or an anti-predation strategy by pilot whales. Recently, an adult female Icelandic killer whale was observed with a newborn pilot whale traveling alongside her in the mother-child position, leading to speculation that the relationship between the two species may be much more complex than previously suggested. This same killer whale was seen a year later interacting with a larger group of these pilot whales. It is not known whether the newborn puppy was adopted or kidnapped.
Behaviorally, these pilot whales can often be seen lobtailing and spyhopping. Additionally this species is known for mass strandings. During a specific time of year, approximately from December to March, these specimens wash up in large numbers along the coast of New Zealand. The reasons for stranding are not entirely clear, but as they have strong social ties, it is speculated that when one animal becomes stranded, the rest of the group may have a tendency to follow.
This species feeds mainly on cephalopods, although in some regions fish may be more important in their diet. Northwest Atlantic specimens are thought to feed predominantly on short-finned squid.
The dives they make to feed, or rather to look for food, can last up to 10 minutes. Their breath exceeds one meter in height. They can also be observed at a depth of 600 metres, but usually their dives go to a few tens of metres.
These pilot whales also make many different types 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 biosonar known as echolocation. This allows individuals to “see” into the dark environments they live in by hearing the nature of the returning echoes.
The whistles and pulsed calls made by pilot whales appear not to fall into distinct types, but rather may be arranged on a continuum. These calls are produced over a wide range of frequencies, which has been observed from less than 1 kHz to approximately 20 kHz.
Recent studies have found that a large part of their vocal repertoire consists of calls produced in repeated sequences. These repetitions are more commonly felt when individuals are socializing than in any other behavioral state (e.g., foraging, traveling, and resting).
Population-wise, while they appear to be abundant, there have been no recent reliable estimates for world population and very little long-term baseline data collected to monitor population trends. However, based on their apparent abundance and available information, they are currently listed by the IUCN as “Least Concern”. Conservative estimates for the population found off Newfoundland were around 13,000 individuals. Another study estimated a total of 780,000 animals in the North Atlantic, although this study includes both short-finned and long-finned pilot whales as they are difficult to distinguish at sea.
As regards the hunting of this species, this has been practiced since the time of the first Norwegian settlements in the Faroe Islands in the North Atlantic. The hunts, called grindadráp in Faroese, mostly take place during the summer. They are generally considered non-commercial – although people may sell their share after the catch has been divided – and organized on a community level. The hunters first surround the specimens with a large semicircle of many boats. The boats then drive the individuals into a bay or to the bottom of a fjord. It is regulated by the Faroese authorities but not by the International Whaling Commission, which does not regulate the hunting of small cetaceans. As of the end of November 2008 the Faroese Chief Medical Officers have recommended that this species is no longer considered fit for human consumption due to the level of mercury found.
While the Faroe Islands are home to the world’s only remaining large-scale pilot whale hunts, this species has historically been hunted elsewhere as well. An industrial fishery was started in the Trinity Bay area of Newfoundland, Canada in 1947 by a Norwegian whaling captain. Catches increased each year until about 10,000 specimens were successfully caught and killed in 1956. This species has also historically been hunted along the coast of New England.
Guido Bissanti
Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Facilidad Global de Información sobre Biodiversidad.
– Gordon Corbet, Denys Ovenden, 2012. Guide to mammals of Europe. Franco Muzzio Publisher.
– John Woodward, Kim Dennis-Bryan, 2018. The Great Encyclopedia of Animals. Gribaudo Publisher.
Photo source:
– https://www.artsobservasjoner.no/MediaLibrary/2020/12/c430b739-192b-42fe-a075-04c423bec252_image.jpg