Sowerby’s Beaked Whale – Mesoplodon bidens
Habitat: Mostly inhabits deep ocean basins and trenches with depths of 700 m or more.
Description: Long, slender, dark grey body, paler below with light spots and – especially in males – linear scars over back and sides. Younger animals have lighter bellies, fewer spots. Head is small with bulge in front of crescent-shaped blowhole, well-defined slender beak. Pair of throat grooves form v-shape. Relatively small flippers, often tucked into flipper pockets. Dorsal fin triangular or slightly sickle shaped, almost 2/3 along back. Flukes are un-notched, trailing edge slightly concave. Pair of triangular teeth visibly protrude over top jaw about half-way down the length of the mouth, only in adult male.
Size: 4.5 – 5 m
Weight: Estimated 1000 – 1400 kg
Distribution: Only known in temperate north Atlantic, mainly in European waters; distribution presumably centred on deep waters of the mid and east Atlantic. Rarely seen (or, at least, identified) around the British Isles but the approximately 80 strandings that have occurred between 1913 – 2007 occurred mainly in N Isles, N & W Scotland, and along the east coast of Great Britain, but also from English Channel, west Ireland. Strandings have occurred in all months, mostly July – November.
Diet & Feeding: Little known. Probably favours squid, some fish.
Breeding: Virtually unknown. Mating and births may occur in late winter and spring. No data on gestation or lactation periods, or calving interval.
Conservation Status & Population: Listed by IUCN as data deficient. No population estimates; pelagic distribution and difficulty in observing and identifying at sea may mean that the species is more common than the few records suggest. Historically hunted off Newfoundland. Currently occasionally caught in fishing gear including gill nets. Sound from oil and gas exploration west of British Isles may pose a threat. Military sonar in mid-frequency range probably more important. One individual identified as victim of ship strike.
Rarely seen at sea. Difficult to distinguish from other Mesoplodon species – it is darkly coloured, with a prominent forehead, sickle-shaped dorsal fin, and inconspicuous blow. Long, slender beak, moderately arched lower jaw, and visible teeth in adult male are diagnostic.