Sowerby's Beaked Whale

Classification

Class: Mammalia
Order: Cetacea
Suborder: Odontoceti
Family: Ziphiidae
Genus: Mesoplodon
Species: bidens
Common Names: Sowerby's beaked whale
Irish Name: Míol mór socach na Mara Thuaidh
 

Key Identification Features

Max. adult body length/weight:6.7m/1,300kg
Average adult body length/weight:5m / 1,100kg
Average length/weight of calf at birth:2.4m/170kg
Blow: Faint and inaudible, even at close range.
Head: A definite bulge is present just in front of the blowhole. The beak is long and slim. The lower jaw slightly protrudes beyond the upper.
Dorsal Fin: Small fin located two-thirds of way along the back.
Colouration: Bluish to dark grey but younger animals tend to have lighter bellies. All individuals have white areas on the lower jaw.
Markings: As they grow older they become progressively more scarred with rake marks and white, oval rings caused by parasites.
 

Field Identification

Give the impression of being sleeker or more streamlined than many of the beaked whales. Adult males have a single, triangular tooth that juts up a little over half-way along each side of the lower jaw. This is diagnostic.
 

Species Similar in Appearance

Other Mesplodon species.
 

Behaviour

When surfacing the bulbous brow and beak tend to break the water. The smooth back then rolls through the water until the small dorsal fin appears. The surfacing sequence is described as being similar to that of a minke whale. They spend about a minute at the surface, with 4-6 quick breaths before diving for 10-15 minutes. High frequency sound is used for echolocation and they have keen hearing and good eyesight.
 

Status and Distribution

They are a North Atlantic species and are one of the most commonly reported beaked whales. Strandings have been recorded from Norway, Sweden, Denmark, Holland, Belgium, Baltic Germany, North France, North Sea coasts of Britain and the Irish West coast (about 100 strandings in all). The fact that relatively few strandings are reported from the US & Canada (approx. 10 sightings) suggests their centre of distribution lies in the North East Atlantic. The population size is unknown.
 

Where and When Best Seen in Ireland

Apart from four sightings along the west and south coasts, little is known about Sowerby's beaked whale in Irish waters. It may be more common here than records suggest, though it's main distribution in Irish waters lies in deep waters off the edge of the continental shelf. It has been recorded during recent surveys off the shelf edge. Animals may migrate southward in winter and closer to shore during summer months.
 

Food and Feeding

Their main food is squid and small fish.
 

Reproduction and Life Cycle

Max. life expectancy:At least 35yrs.
Average life expectancy: Unknown.
Mating Occurs: Unknown.
Season of birth: Winter.
Gestation: Unknown.
 

Social Structure

They appear to be mainly solitary animals, sometimes forming pairs or small groups. Males fight over females and older animals may show many scars from such interactions.
 

Conservation Issues

Not enough is know about these animals to determine the threats to them, although new trends in deep water trawling may pose a threat, as these whales rely on deep-water canyons as primary habitat. They were hunted in the past off Newfoundland, but are not the subject of any systematic hunt at present. Another significant threat in Irish waters is noise pollution from off-shore exploration and drilling along the West Coast.
 

Stranded Animals

A pair of throat grooves are present as are flipper pockets. The flippers are rounded with a pointed tip. This species lacks a central tail notch characteristic of most mesoplodon species. Adult males have a single, triangular tooth that appears to lie mid-way along each side of the lower jaw in live animals but in the skeleton is actually around 30cm from the tip of the lower jaw. The teeth are around 10cm high. The tip leans slightly towards the back of the mouth. The sound of live stranded Sowerby's beaked whales has been likened to a cow's “mooing”.
 

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