Sowerby's beaked whale | |
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Size compared to an average human | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Infraorder: | Cetacea |
Family: | Ziphiidae |
Genus: | Mesoplodon |
Species: | M. bidens |
Binomial name | |
Mesoplodon bidens Sowerby, 1804 | |
Sowerby's beaked whale (Mesoplodon bidens), also known as the North Atlantic or North Sea beaked whale, is a species of toothed whale. It was the first mesoplodont whale to be described. James Sowerby, an English naturalist and artist, first described the species in 1804 from a skull obtained from a male that had stranded in the Moray Firth, Scotland, in 1800. He named it bidens, which derives from the two teeth present in the jaw, now known to be a very common feature among the genus. [3]
Sowerby's beaked whale has a typical body shape for the genus, and is mainly distinguished by the male's dual teeth positioned far back in the mouth. The whale's beak is moderately long, and the melon is slightly convex. The colouration pattern is a grey with light countershading on the bottom, and frequently has cookiecutter shark bites and scars from teeth (in males). The whale reaches 5 metres (16 ft) in females and 5.5 metres (18 ft) in males, with a weight of 1000-1300 kilograms (2200-2900 lb). The gestation period lasts for 12 months and the young are born at a length of 2.4 to 2.7 metres (8 to 9 ft) with a weight of around 185 kilograms (400 lb).
The diet of Sowerby's beaked whales consists primarily of small mesopelagic and benthopelagic fish, with cephalopods accounting for a much smaller proportion of the diet. [4]
Sowerby's beaked whale ranges from Nantucket to Labrador in the western North Atlantic and from Madeira to the Norwegian Sea in the eastern North Atlantic. They typically range in waters 200 to 1,500 metres (650 to 5,000 ft) deep. No population estimates have been made. In 1991, there were about 90 records of the species, 80 from the eastern North Atlantic and less than ten from the western North Atlantic; the majority of the records are from around the British Isles. [5]
On 10 January 2009, a female Sowerby's beaked whale was found at the port of Fethiye on the Aegean coast of Turkey, far away from her natural habitat. The whale was successfully saved and released back to the open sea. [6]
On 25 July 2015, biologists with the New England Aquarium investigated the death of a beaked whale in Massachusetts. The carcass of the 17 ft (5.2 m) long female, which weighed almost 1 short ton (0.91 t), was found on Plymouth Long Beach in Plymouth, Massachusetts. Biologists from the aquarium and the International Fund for Animal Welfare said they would perform a necropsy at the Woods Hole Oceanographic Institution. The whale was initially identified as a Sowerby's beaked whale, but the aquarium said a more thorough examination and consultation with additional experts was needed as staff had not seen a beaked whale since 2006. [7]
On 26 October 2018, a 4.2 m (14 ft) whale was found beached near the town of Saltdean, on the UK coast. The carcass was subsequently taken to the Natural History Museum, London for post-mortem. [8] On 29 August 2019, a stranded whale was rescued from Dungarvan Bay, in southeast Ireland. [9] On 4 July 2020, a whale became disorientated and strayed into Wicklow, harbour on the east coast of Ireland but was later discovered dead on Wicklow, beach. [10]
On 21 August 2020, a 3.86 m (12.7 ft) long female Sowerby's beaked whale washed up on the shore of a beach in Caister-on-Sea, Norfolk. Emergency services assisted the whale out to sea in an attempt to encourage the animal to live. Unfortunately the next morning a report was received to suggest the whale was stranded and deceased at Lowestoft, on the UK coast, following reported sights of 2 whales in the nearby towns of Brancaster and Blakeney in Norfolk earlier in the month. [11]
On successive days in October 2020, two Sowerby's beaked whales were washed up on separate beaches in East Lothian. Both animals died. [12] The necropsy revealed that one of the whales had an unusually high density of small gas bubbles in the lung tissue, and both whales showed signs of gas emboli in the mesenteric arteries. These symptoms are often associated with decompression sickness, however it was not clear if this was the cause in this case. The MOD later revealed that, one day before the first whale stranded, airborne ASW sonar exercises had been carried out within 80 nmi (150 km; 92 mi) of the stranding sites. There was not enough evidence from the necropsy to confirm decompression sickness as the cause of death, so the Scottish Marine Animal Stranding Scheme still consider these as live strandings. However, given the otherwise good physical health of the beaked whales combined with the unusual proximity in both time and location of their strandings, the use of sonar in the surrounding area should still be considered a possible factor in the stranding. [13]
Sowerby's beaked whales are reclusive creatures that stay away from ships and are rarely sighted. The whales are occasionally seen in groups of up to 10 individuals (males, females, and calves) and have been known to strand in groups as well. They hunt at depths greater than 500m, and dive to more than 1000m while foraging. Their swimming and diving behaviours are more similar to deep-diving delphinids such as Risso's dolphins and pilot whales than to other mesoplodonts. Compared to Blainville's beaked whales, a mesoplodont of similar body size, Sowerby's beaked whales swim faster while descending and while actively foraging. Their dives are also relatively short and generally last between 30 and 40 minutes. Sowerby's beaked whales cover long distances between dives by swimming at speed just below the surface of the water, as opposed to the typical beaked whale strategy, where time near the surface is minimised by travelling on shallow dives at depths between 100 and 200m. [14]
The species has been hunted infrequently by Norwegians, but such practices have long since been abandoned. There are some deaths due to entanglement in fishing gear, but it is unlikely to be very damaging to the species.[ citation needed ] Sowerby's beaked whale is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS) [15] and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS). [16] The species is further included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU). [17]
Beaked whales are a family of cetaceans noted as being one of the least-known groups of mammals because of their deep-sea habitat, reclusive behavior and apparent low abundance. Only three or four of the 24 existing species are reasonably well-known. Baird's beaked whales and Cuvier's beaked whales were subject to commercial exploitation, off the coast of Japan, while the northern bottlenose whale was extensively hunted in the northern part of the North Atlantic in the late 19th and early 20th centuries.
Andrews' beaked whale, sometimes known as the deep-crest beaked whale or splay-toothed whale, is one of the least known members of a poorly known genus. The species has never been observed in the wild, and is known only from specimens washed up on beaches.
Mesoplodont whales are 16 species of toothed whale in the genus Mesoplodon, making it the largest genus in the cetacean order. Two species were described as recently as 1991 and 2002, and marine biologists predict the discovery of more species in the future. A new species was described in 2021. They are the most poorly known group of large mammals. The generic name "mesoplodon" comes from the Greek meso- (middle) - hopla (arms) - odon (teeth), and may be translated as 'armed with a tooth in the centre of the jaw'.
Hubbs' beaked whale was initially thought to be an Andrews' beaked whale when discovered by ichthyologist Carl Hubbs; however, it was named in his honor when it was discovered to be a new species. This species has the typical dentition found in the genus, but its main outstanding features are a white "cap" on the head and very extensive scarring. The species is known from 31 strandings, a few at-sea sightings, and observations of two stranded whales that were kept in captivity for 16–25 days.
Blainville's beaked whale, or the dense-beaked whale, is believed to be the widest ranging mesoplodont whale. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw — the heaviest bone he had ever come across — which resulted in the name densirostris. Off the northeastern Bahamas, the animals are particularly well documented, and a photo identification project started sometime after 2002.
Gervais's beaked whale, sometimes known as the Antillean beaked whale, Gulf Stream beaked whale, or European beaked whale is the most frequently stranding type of mesoplodont whale off the coast of North America. It has also stranded off South America and Africa.
The ginkgo-toothed beaked whale is a poorly known species of whale even for a beaked whale, and was named for the unusual shape of its dual teeth. It is a fairly typical-looking species, but is notable for the males not having any scarring.
Gray's beaked whale, sometimes known as Haast's beaked whale, the scamperdown whale, or the southern beaked whale, is one of the better-known members of the genus Mesoplodon. This species is fairly gregarious and strands relatively frequently for a beaked whale. In the Māori language, this species is called hakurā or iheihe.
Hector's beaked whale, is a small mesoplodont living in the Southern Hemisphere. This whale is named after Sir James Hector, a founder of the colonial museum in Wellington, New Zealand. The species has rarely been seen in the wild.
The strap-toothed beaked whale, also known as Layard's beaked whale, is one of the largest members of the mesoplodont genus, growing to 6.2 m (20 ft) in length and reaching up to 1,300 kg (2,900 lb). The common and scientific name was given in honor of Edgar Leopold Layard, the curator of the South African Museum, who prepared drawings of a skull and sent them to the British taxonomist John Edward Gray, who described the species in 1865.
True's beaked whale is a medium-sized whale in the genus Mesoplodon. It is native to the northern Atlantic Ocean. The common name is in reference to Frederick W. True, a curator at the United States National Museum.
The tropical bottlenose whale, also known as the Indo-Pacific beaked whale or Longman's beaked whale, was considered to be the world's rarest cetacean until recently, but the spade-toothed whale now holds that position. As of 2010, the species is now known from nearly a dozen strandings and over 65 sightings. This is the only species in the genus Indopacetus.
The pygmy beaked whale, also known as the bandolero beaked whale, Peruvian beaked whale and lesser beaked whale, is the smallest of the mesoplodonts and one of the newest discoveries. There were at least two dozen sightings of an unknown beaked whale named Mesoplodon sp. A before the initial classification, and those are now believed to be synonymous with the species. The species was formally described in 1991, based on ten specimens obtained from Peru between 1976 and 1989, including a 3.72 m (12.2 ft) adult male as the type specimen. A specimen that stranded at Paracas, Peru in 1955 has since been identified as a pygmy beaked whale. Since 1987, there have been an additional 40 sightings of the species, for a total of 65.
Stejneger's beaked whale, also known as the Bering Sea beaked whale or the saber-toothed whale, is a relatively unknown member of the genus Mesoplodon inhabiting the North Pacific Ocean. Leonhard Hess Stejneger collected the type specimen on Bering Island in 1883, from which Frederick W. True provided the species' description in 1885. In 1904, the first complete skull was collected, which confirmed the species' validity. The most noteworthy characteristic of the males is the very large, saber-like teeth, hence the name.
The Cuvier's beaked whale, goose-beaked whale, or ziphius is the most widely distributed of all beaked whales in the family Ziphiidae. It is smaller than most baleen whales yet large among beaked whales. Cuvier's beaked whale is pelagic, inhabiting waters deeper than 300 m (1,000 ft). It has the deepest and longest recorded dives among whales at 2,992 m (9,816 ft) and 222 minutes, though the frequency and reasons for these extraordinary dives are unclear. Despite its deep-water habitat, it is one of the most frequently spotted beaked whales.
The four-toothed whales or giant beaked whales are beaked whales in the genus Berardius. They include Arnoux's beaked whale in cold Southern Hemispheric waters, and Baird's beaked whale in the cold temperate waters of the North Pacific. A third species, Sato's beaked whale, was distinguished from B. bairdii in the 2010s.
The northern bottlenose whale is a species of beaked whale in the ziphiid family, being one of two members of the genus Hyperoodon. The northern bottlenose whale was hunted heavily by Norway and Britain in the 19th and early 20th centuries. It is one of the deepest-diving mammals known, reaching depths of 2,339 m (7,674 ft) and capable of diving for up to 130 minutes.
Perrin's beaked whale is part of the toothed whale suborder and is one of over 90 known cetaceans in existence today. Beaked whales are part of the family Ziphiidae, which are the second most diverse group out of all marine mammals with over 20 species currently recognized. Although diverse, little is understood about these timid, deep divers that can dive for up to two hours. The whales are partially named after their beak shaped jaw, which extends from their small head. The genus name Mesoplodon comes from the Greek meanings of meso- (middle), - hopla (arms), - odon (teeth), and may be translated as 'armed with a tooth in the center of the jaw'.
The spade-toothed whale is a very little-known species, the rarest species of beaked whale.
Deraniyagala's beaked whale is a species of mesoplodont whale closely related to the ginkgo-toothed beaked whale.
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