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Overview

Brief Summary

Worldwide, there are many species of beaked whales, all looking very much alike. There is hardly anything known about these mysterious whales, except that they are very shy. In the North Sea, Sowerby's beaked whales are seen most often. They are even found regularly in the extreme northern part of the North Sea, but are rarely observed in the south. In general, Sowerby's are found mostly in the northern Atlantic Ocean and the Mediterranean Sea.
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Description

"Most stranded Sowerby's beaked whales have been found on the coast of the British Isles, and the North Sea may be the center of the species' distribution. We know very little about this whale, including what it eats and details of its growth, reproduction, and social organization. Adults are slightly more than 5 m in length and have bluish-gray or slate gray backs; calves are reported to be about 2.4 m long at birth. Stranded whales have been heard making cow-like vocalizations. At sea, this whale can be identified by its long snout. Adult males have distinctive, tall teeth that slant out and up from the sides of the jaw about a third of the way back from the front end of the mouth."

Adaptation: The odd, single-toothed skull of a Beaked whale, Mesoplodon, is an example of the strange skull shapes that have evolved among cetaceans.

Links:
Mammal Species of the World
  • Original description: True, F.W., 1913.  Smithsonian Miscellaneous Collections, 60(25):1.
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Threats

By catch from fishing gear, such as driftnets and gillnets off the U.S. Atlantic coast

Hunting, cetaceans are targeted in Newfoundland and by Norwegian whalers off of Iceland and in the Barents Sea

Underwater sounds and anthropogenic noise - anthropogenic noise levels in the world's oceans are an increasing habitat concern, particularly for deep-diving cetaceans like Sowerby's beaked whales that use sound to feed, communicate, and navigate in the ocean

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Comprehensive Description

Description

 Mesoplodon bidens is a toothed whale and can be recognised as such by the single blowhole and the presence of teeth (rather than baleen). It is a member of the beaked whale family with the characteristic V-shaped crease on the throat and the short dorsal fin set relatively far back. Sowerby's beaked whale is a small beaked whale that can reach up to 5.5 m in length. The lower jaw has a single pair of teeth (exposed only in adult males). The forehead rises at a shallow angle and has a slight bump. It has a distinct beak and the mouthline is curved down at rear. Sowerby's beaked whale has a charcoal grey dorsal and lateral colouration with a lighter belly. Adults may also have light grey spots on the body and are often covered with scratches and scars.Sowerby's beaked whale may be confused with True's beaked whale Mesoplodon mirus but can be recognised by a slight bump on the forehead and a slightly longer beak. Sowerby's beaked whales are usually found either alone or in groups of up to 10 individuals. Little is known about their behaviour although tail-slapping has been recorded. Dives may last up to 15 minutes long (Kinze, 2002).
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Description

Species Description

Weight: 2,200-2,900 lbs (1,000-1,315 kg)

Length: 14.5-21 ft (4.5-5.5 m)

Appearance: small to medium-sized charcoal gray body with a very long, slender beak and a bulge on the forehead area

Lifespan: unknown, but sexually mature at around 7 years

Diet: small fish like Atlantic cod and cephalopods like squid

Behavior: they have a low profile at the surface and a small, inconspicuous blow, making them difficult to observe and identify at sea

Sowerby's beaked whales, sometimes known as the "North Atlantic beaked whale," are little known members of the beaked whale family (Ziphiidae). As adults, Sowerby's beaked whales can reach estimated lengths of 14.5-21 ft (4.4-5.5 m) and weigh 2,200-2,900 lbs (1,000-1,318 kg). Males, which are generally larger, can be distinguished from females and juveniles by a pair of visible teeth that erupt from the slightly arched lower jaw. Females and juveniles have teeth as well, but the teeth remain hidden beneath the gum tissue of the mouth, and their jawline is straight. This species of beaked whale is difficult to observe and identify at sea due to a low profile at the surface and a small, inconspicuous blow.

Sowerby's beaked whales have a small to medium-sized body with a very long, slender beak relative to other mesoplodonts, as well as a bulge on the forehead area. The beak often emerges at a steep angle when surfacing. They have a small, wide-based, slightly "falcate" "dorsal" fin located far down (about two-thirds) the animal's back. Most of the body has a charcoal gray coloration with a pale underside. The lower jaw is usually light gray or white. Calves are generally darker than adults. This species has less visible scarring than most other beaked whale species.

Many species of beaked whales (especially those in the genus Mesoplodon) are very difficult to distinguish from one another (even when dead). At sea, they are challenging to observe and identify to the species level due to their cryptic, skittish behavior, a low profile, and a small, inconspicuous blow at the waters surface; therefore, much of the available characterization for beaked whales is to genus level only. Uncertainty regarding species identification of beaked whales often exists because of a lack of easily discernable or distinct physical characteristics.

Sowerby's whales are usually found individually or in small, closely associated groups averaging between 3-10 individuals. Regular dives range from 10-15 minutes, but dives of at least 28 minutes reaching depths up to 4,920 ft (1,500 m) have been recorded. While diving, they use suction to feed on small fish (e.g., Atlantic cod) and cephalopods (e.g., squid) in deep waters.

Sowerby's beaked whales may reach sexual maturity at about 7 years of age. Their breeding season may be from late winter to spring. A sexually mature female will give birth to a single newborn calf that is about 8-9 ft (2.4-2.7 m) long and weighs about 375 lbs (170 kg). The estimated lifespan of this species is unknown.

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Distribution

occurs (regularly, as a native taxon) in multiple nations

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Global Range: Mainly in cooler offshore waters of North Atlantic and Baltic Sea; a report for the coast of Italy may be valid; more common in European waters than in American waters, where single strandings have been recorded for near Nantucket, Massachusetts, and in eastern Canada (Mead and Brownell, in Wilson and Reeder 1993). Range may be centered in the North Sea. See Bonde and O'Shea (1989) for information on a 1984 stranding in Florida (regarded as a stray). Poorly known; as of late 1980s, less than 40 published stranding records, 11 in North America (Bonde and O'Shea 1989; 1990, Can. Field-Nat. 104:414-420). See Lien and Barry (1990) for information on status in Canada. Hooker and Baird (1999) described recent observations of groups of individuals in the Gully, Nova Scotia.

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North Atlantic (Eastern and Western), including North sea; considered rare in Canadian waters
  • North-West Atlantic Ocean species (NWARMS)
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Range Description

Sowerby's beaked whales are known almost exclusively from the colder waters of the North Atlantic, from at least Massachusetts, USA to Labrador, Canada in the west, and from Iceland to Norway in the east (Mead 1989; MacLeod et al. 2006). This is the most northerly distributed of the Atlantic species of Mesoplodon, with most records north of 30°N. There are a number of strandings or sightings considered to be extralimital in the Mediterranean Sea, and from the Gulf of Mexico side of Florida.
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Geographic Range

Sowerby's beaked whales are found in temperate to sub arctic waters in the eastern and western North Atlantic. They are found around the British Isles and are known to occur from Newfoundland to Massachusetts. Sowerby's beaked whales occur as far north as Labrador in the west and in the Norwegian Sea in the east, southern limit is thought to be somewhere between 33ºN and 41ºN.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); atlantic ocean (Native )

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Stranding Distribution

Found in the temperate waters of the North Atlantic Ocean. Stranding records are more common in the eastern North Atlantic, with the bulk of stranding records from the British Isles and North Sea.

The northern limit in the eastern Atlantic extends to 71o 30’ N in the Norwegian Sea; the western Atlantic range extends to Labrador. The southern limit lies between 33o and 41o N. Stranding records from Florida are probably extralimital. Water depths where sightings have occurred range from 200 to 1500 m.

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Sowerby's beaked whales are distributed throughout the North Atlantic Ocean (30-71° North), which includes the Norwegian Sea, Labrador Sea, Iceland, Baltic Sea, and south to Massachusetts, Madeira, and the Canaries. Reports of this species in Canadian waters are considered rare. They are not known to occur in the Mediterranean Sea. Strandings have occurred in Florida and Italy, but these are considered outside their normal range. Their distribution may vary depending on the movements of oceanographic currents. There are no known seasonal movements or migrations for this species.

Population Trends

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Physical Description

Morphology

Physical Description

Mesoplodon bidens is bluish grey to slate grey in color, with a lighter underside, grey and white spots may be present on the body with limited scaring. Mesoplodon bidens have a long slender beak that contains a pair of teeth midway up the lower jaw. They have a long think body, long flippers for the Mesoplodon family, and no notch in the fluke. The dorsal fin is quite small with a rounded tip and may appear falcate. Young M. bidens have a light blusih grey to white underside, more prominant than in adults.

Range mass: 1000 to 1300 kg.

Range length: 5 to 5.5 m.

Sexual Dimorphism: male larger

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Tooth morphology

Tooth position

A single pair of teeth is positioned midway between the apex of the beak and the posterior end of the mouth.

Tooth exposure

Erupted teeth in adult males are covered by gum tissue, with only the tip of tooth exposed. Teeth do not erupt in females or juveniles.

Tooth shape

In lateral profile, the anterior margin is weakly sinusoidal (convex proximally, concave distally) and is longer than the strongly convex posterior margin. A denticle is positioned at the top of the anterior edge of the tooth. When the denticle is not excessively worn, it extends well past the antero-dorsal edge of the tooth.

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Skull morphology

Diagnostic features of the skull and mandible

On the vertex of the dorsal skull, the premaxillary bone extends forward of the nasal and frontal. Separates from Berardius and Ziphius.

A sulcus (groove) running along the middle of the combined surfaces of the nasal bones so depresses their middle that it is the lateral portion of each nasal bone that reaches farthest forward on the vertex. Separates from Tasmacetus and Indopacetus.

When the skull is upright and the long axis of the anterior half of the beak is horizontal, a horizontal plane transecting the summit of either maxillary prominence transects the mesethmoid bone. Separates from Hyperoodon.

Tooth alveoli of mandible overlap or are positioned slightly anterior to the mandibular symphysis. Separates from Berardius, Ziphius, Tasmacetus, Indopacetus, Hyperoodon, M. hectori, M. mirus, M. perrini, M. densirostris, M. ginkgodens, M. peruvianus, and M. stejnegeri

Basirostral groove absent or present as a shallow groove that does not extend past the prominental notch. Separates from M. grayi and M. layardii.

The maxillary prominences rise less than 10 mm higher than the height of the premaxillaries where the latter passes between the former. Separates from M. bowdoini, M. carlhubbsi, and M. europaeus.

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External Morphology

Head Shape

Melon is convex, though not bulbous and is defined posteriorly by the indentation at the blowhole. The forehead merges seamlessly to the long, narrow beak. The mouthline is sinusoidal, but not strongly arched.

Coloration

Dorsal coloration is bluish-gray or slate. Sides are lighter, grading to a white ventral surface. Gray or white scars, visible as linear streaks or round / oval spots, may be distributed irregularly on sides. This pattern is the same for both sexes.

Size

Adult body length ranges between 4.5 to 5.5 m. Recorded maximum body length for adult males and females is 5.5 m and 5.2 m, respectively. Body length at birth is 2.4 m.

Most Likely Confused With:

Mesoplodon europaeus

Mesoplodon mirus

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Size

Length: 4900 cm

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Size in North America

Length:
Range: 5.5 m males; 5.1 m females

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Ecology

Habitat

Habitat Type: Marine

Comments: Deeper areas of the open ocean.

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offshore
  • North-West Atlantic Ocean species (NWARMS)
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also in shelf areas
  • UNESCO-IOC Register of Marine Organisms
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Habitat and Ecology

Habitat and Ecology
As with other members of the genus, these whales occur almost exclusively in deep waters past the continental shelf edge. Although it is one of the most commonly stranded Mesoplodon species, there have been few sightings at sea, and it is poorly known. De Buffrénil (1995) mentioned that two sightings were north of Scotland and west of the Orkney Islands, in waters several 100 m deep. Hooker and Baird (1999) observed groups of Sowerby's Beaked Whales in the Gully, a submarine canyon off eastern Canada, on four occasions. Sightings were in water depths of between 550 m and 1,500 m.

Ostrom et al. (1993) evaluated the diet of Sowerby's beaked whales, based on isotopic comparisons among northwestern Atlantic cetaceans. They feed on squid and fish, including Atlantic cod (Gadus morhua).

Systems
  • Marine
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Sowerby's beaked whales are found in cool to warm temperate offshore waters of the North Atlantic Ocean. They are usually observed in open water and most often seen in areas were depths range from 198 to 1524 m.

Range depth: 198 to 1524 m.

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: pelagic

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Depth range based on 34 specimens in 1 taxon.
Water temperature and chemistry ranges based on 26 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 9.488 - 19.052
  Nitrate (umol/L): 1.393 - 9.648
  Salinity (PPS): 33.265 - 35.293
  Oxygen (ml/l): 5.437 - 6.344
  Phosphate (umol/l): 0.248 - 0.683
  Silicate (umol/l): 1.541 - 3.866

Graphical representation

Temperature range (°C): 9.488 - 19.052

Nitrate (umol/L): 1.393 - 9.648

Salinity (PPS): 33.265 - 35.293

Oxygen (ml/l): 5.437 - 6.344

Phosphate (umol/l): 0.248 - 0.683

Silicate (umol/l): 1.541 - 3.866
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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 Sowerby's beaked whale is an oceanic and coastal species that may be seen at the surface but little is known on what depth they may dive to.
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Sowerby's beaked whales prefer the deep, cold temperate and subarctic waters of the North Atlantic Ocean, but have been reported near the ice pack as well.

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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Trophic Strategy

Comments: Diet probably includes small offshore squid (Ostrom et al., 1993, Can. J. Zool. 71:858-861) and deepwater fishes.

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Food Habits

The diet of Sowerby's beaked whales consists mostly of squid, octopus, and fish. A necropsy of one individual showed stomach contents that included bottom-dwelling and deep water fish.

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore , Molluscivore )

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Associations

Ecosystem Roles

Little is known about the role of Sowerby's beaked whales in the northern Atlantic ecosystem. They are undoubtedly predators of marine organisms.

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Predation

There is no information about predation on Sowerby's beaked whales. Once they reach their adult size it is likely that they are protected from much predation. Killer whales and large sharks may target Sowerby's beaked whales.

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General Ecology

Not highly gregarious; found alone or in groups of up to 8-10 individuals (Hooker and Baird 1999).

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Life History and Behavior

Behavior

Diet

squid and small fish
  • North-West Atlantic Ocean species (NWARMS)
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Communication and Perception

A young animal, that was kept in a dolphinarium for a few hours, was recorded using high frequency sound pulses to echolocate.

Communication Channels: acoustic

Perception Channels: visual ; acoustic ; echolocation

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Cyclicity

Comments: Active day/night.

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Life Expectancy

Lifespan/Longevity

The is no data on the lifespan in M. bidens.

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Reproduction

Limited data suggest that mating and birth ocuur in late winter and spring. Gestation lasts about 1 year.

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Nothing is known about the mating systems of M. bidens.

Little in known about general reproductive behavior of M. bidens. Mating is thought to occur in late winter, with births late in spring and gestation lasting about 12 months. Young are about 2.4 to 2.7 meters in length and weigh about 185 kg.

Breeding interval: Breeding interval is not known for Sowerby's beaked whales.

Breeding season: Mating is thought to occur in late winter.

Average number of offspring: 1.

Average gestation period: 12 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Sowerby's beaked whale females provide milk for their young and protect them. There is no other available information on parental investment.

Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Occurs mainly in cooler offshore waters of North Atlantic and Baltic Sea; more common in European waters than in American waters, where single strandings have been recorded for near Nantucket, Massachusetts, and in eastern Canada; poorly known--as of late 1980s, less than 40 published stranding records, 11 in North America.

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IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L.

Reviewer/s
Hammond, P.S. & Perrin, W.F. (Cetacean Red List Authority)

Contributor/s

Justification
There is no information on global abundance or trends in abundance for this species. It is not believed to be uncommon but it is potentially vulnerable to low-level threats and a 30% global reduction over three generations cannot be ruled out (criterion A).

History
  • 1996
    Data Deficient
  • 1994
    Insufficiently Known
    (Groombridge 1994)
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There is very little data on Sowerby's beaked whales. As a result there is little information on population sizes, current or historic, to determine conservation status. This species is rarely seen in the open ocean, most records are from strandings.

US Federal List: no special status

CITES: appendix ii

State of Michigan List: no special status

IUCN Red List of Threatened Species: data deficient

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Population

Population
Very little is known of the population biology of this species. It is one of the most commonly seen mesoplodonts in some parts of its range.

Population Trend
Unknown
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Population Trends

For management purposes, Sowerby's beaked whales inhabiting U.S. waters have been placed in the Western North Atlantic stock. No current population estimates are available for this species of beaked whale. The status of the stock is unknown, but is classified as "strategic." This species may be relatively abundant in the North Sea. There are insufficient data to determine the population trends for this species, but they are probably not rare.

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Threats

Major Threats
There is little specific information on the status or threats to whales of this species (Reeves et al. 2003). However, some are known to have been incidentally killed by whalers in Newfoundland, Iceland, and in the Barents Sea. A few entanglements in fishing gear (e.g., driftnets) have been documented. Waring et al. (2001) reported that for 1989-1998 observed bycatch in pelagic drift gillnets along the US East Coast amounted to 24 Sowerby's beaked whales. These were caught exclusively in the area from Georges Canyon to Hydrographers Canyon, along the continental shelf break and continental slope during July-October. This fishery has now been closed.

This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).

Evidence from stranded individuals of several similar species indicates that they have swallowed discarded plastic items, which may eventually lead to death (e.g. Scott et al. 2001); this species may also be at risk.

Predicted impacts of global climate change on the marine environment may affect this species of whale, although the nature of impacts is unclear (Learmonth et al. 2006).
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Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES. Research is needed to determine the impacts of potential threatening processes on this species.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Sowerby's beaked whales are occasionally caught in fishing gear, damaging nets in the process. Arguably this is more traumatic for the whales than fishing crews.

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Economic Importance for Humans: Positive

Sowerby's beaked whales were once infrequently harvested by Norwegian whalers. They are no longer hunted actively.

Positive Impacts: food

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Risks

IUCN Red List Category

Data Deficient (DD)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

Sowerby's beaked whale

Sowerby's beaked whale!<-- This template has to be "warmed up" before it can be used, for some reason -->

Sowerby's beaked whale (Mesoplodon bidens), also known as the North Atlantic/North Sea beaked whale, was the first beaked whale to be described. Its name, bidens, derives from the two teeth present in the jaw, now known to be a very common feature among the genus.

Contents

Physical description

Profile of an adult female

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 cookie cutter 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).

Population and distribution

Sowerby's beaked whale ranges from Nantucket to Labrador in the Western Atlantic and from Madeira to the Norwegian Sea in the Eastern Atlantic. They typically range in waters 200 to 1,500 metres (650 to 5,000 ft) deep. No population estimates have been made.

On January 10, 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.[1] In August of the same year, a Sowerby's beaked whale was found on the beach at Blakeney Point in Norfolk, England by holiday makers including a Mr. A. Davies and associates. The tide was rapidly receding, and being watched by a Seal Tour Boat, they managed to return the whale to the sea using a stretcher used for injured seals. All worked extremely hard, and their work paid off as the whale was returned safely out to sea.[citation needed]

Behaviour

Sowerby’s beaked whales are reclusive creatures that stay away from ships and are rarely sighted. The whales are occasionally in groups of 8 to 10 individuals (males, females, and calves) and have been known to strand in groups as well. They are believed to primarily feed on squid and molluscs, but cod has also been found in their stomachs. They have been known to dive down at times approaching 30 minutes.

Conservation

Skull of Sowerby's beaked whale.

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.

Notes

  1. ^ Hürriyet daily newspaper: "Balinaymış". Published on January 12, 2009. Retrieved on January 12, 2009.

References

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Notes

Did you know?

• Sowerby's beaked whale was the first living species of beaked whale to be discovered.

• Sowerby's beaked whale's scientific species name (bidens) is derived from the Latin word bi for "two" and dens for "teeth."

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