White-Beaked Dolphin – Lagenorhynchus albirostris
Habitat: Cool and subarctic waters, usually over the continental shelf.
Description: Very stout, torpedo-shaped body. Rounded snout with short, stubby beak and 22 – 28 pairs of small, pointed teeth in each jaw. Dark grey or black on back, tail, and top of head; dark patch on flank of variable extent below dorsal fin on otherwise pale grey flank. Pale grey to whitish area extends from flanks over orsal surface behind dorsal fin, back to tail stock – this ‘saddle’ is less distinct in younger individuals. Underside is pale grey to white. Beak generally white, but often with dark patches; may apear entirely grey, but always paler in comparison with dorsal surface. Pale eye ring, sometimes connected to beak by thin white line. Flippers and tail blackish; white freckling common on front edge of flippers near base and lower surface of tail. Dorsal fin is centrally placed, tall, sickle-shaped. Tail stock is thick, gradually tapering towards flukes which are slightly notched with concave trailing edges.
Size: 240 – 270 cm (female; max 300 cm), 250 – 280 cm (male; max 310 cm).
Weight: Adult max. 306 kg female (one pregnant female, Netherlands, weighed 387 kg), 354 kg male.
Distribution: Restricted to northern North Atlantic, from south west and east Greenland, Svalbard, Barents Sea, south to Cape Cod USA and Bay of Biscay. Occurs over much of northern European continental shelf. Common in British and Irish waters, most abundantly in central and north North Sea across to west Scotland and Ireland. Occasional off south Ireland in Irish Sea. Similar distribution to Atlantic white-sided dolphin but less pelagic. Recorded throughout year in British waters but largest numbers seen in July – September.
Diet & Feeding: Feeds on great variety of fish. Herds fish cooperatively. Groups seen hunting in broad front, swimming parallel to each other at regular distances; fish shoals then encircled and trapped near surface. Seabirds, particularly gannet, kittiwake, other gulls often associated with feeding white-beaked dolphin groups.
Breeding: Limited data. Births mainly May – August, some September – October. Gestation period around 10 – 11 months; lactation period, calving interval, age at sexual maturity unknown.
Conservation Status & Population: Listed by IUCN as lower risk / least concern. SCANS I Survey in North Sea and adjacent waters in June – July 1994 gave estimate of 7856 white-beaked dolphins, or 11,760 unidentified Lagenorhynchus – great majority of which probably white-beaked. SCANS II in July 2005 covered wider area (south-west Norway, south to Atlantic Portugal) gave estimate of 22,700 individuals. Threats generally poorly known. Organochlorine levels high in sample from Newfoundland, lower in Great Britain, Denmark, USA, although sample sizes small. Small numbers bycaught from midwater trawls and driftnets set mainly for cod, mackerel, salmon, herring. Arthritis and dystocia seems to be more common in this species than other dolphin species.
Large, stout, short-beaked species. Flippers larger, less sickle-shaped than white-sided dolphin. Skull broader and larger than white-sided dolphin, with wider and clearly tapering rostrum and fewer, larger teeth.
Vocalisations: Poorly known. Includes whistles 6.5 – 15 kHz (often around 8 kHz). Echolation clicks up to at least 325 kHz, click bursts of 100 -750 pulses /s.