Lagenorhynchus albirostris (Gray, 1846)

Russell A. Mittermeier & Don E. Wilson, 2014, Delphinidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 410-526 : 489

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White-beaked Dolphin

Lagenorhynchus albirostris

French: Dauphin a bec blanc / German: Weil 3schnauzendelfin / Spanish: Delfin de hocico blanco

Other common names: \White-beaked Porpoise, White-nosed Dolphin

Taxonomy. Delphinus albirostris Gray, 1846 ,

type locality unknown. Later designated by J. E. Gray in 1846 as “North Sea, coast of Norfolk,” England, UK, and further modified by Gray in 1850 to “Great Yarmouth.”

Taxonomy of Lagenorhynchus is currently in dispute. Recent molecular analyses have revealed that the genus is not monophyletic. L. albirostris is the type species, but more recent molecular studies have shown that not all of the other members of the genus are close relatives, so those species will likely be placed into different genera sometime in the near future. L. albirostris may belong to an isolated lineage within Delphinidae . Monotypic.

Distribution. Temperate to subarctic waters of the N Atlantic including S Davis Strait, Gulf of Saint Lawrence, Barents Sea, and North Sea, S to Cape Cod (USA) in the E and the coasts of N France in the W. Extralimital sightings in the Baltic Sea, Bay of Biscay, and Iberian Peninsula.

Descriptive notes. Total length 240-310 cm; weight 180-350 kg. Neonates are 110-120 cm long and weigh c.40 kg. Male White-beaked Dolphins are slightly larger than females. The White-beaked Dolphin has a robust body shape more reminiscent of porpoises ( Phocoenidae ) than other delphinids (ocean dolphins), and a short beak only 5-8 cm long. Dorsal fin and flippers are long and falcate, with pointed tips. Upper flanks and back are black to dark gray, and belly and beak are white to pale gray. Most of the tailstock is pale mottled gray, and a pale gray streak extends anteriorly from this area onto upper flanks in front of dorsal fin. There may also be pale gray streaks around eyes. Dorsal fin, flukes, and flippers tend to be a uniform dark gray, and there may also be a black patch on the chest. There are 22-28 pairs of sharp, conical teeth in each jaw.

Habitat. Throughout North Atlantic Ocean and sometimes at edges of pack ice. Regions of highest White-beaked Dolphin abundance include the Labrador Shelf, Icelandic waters, Scottish waters, and northern coasts of Norway. It seems to prefer waters offshore from and over continental shelves that are 150-1000 m deep and have a seasurface temperature of 5-15°C. Four management units of the White-beaked Dolphin, based on the highest densities, have been distinguished by skull characteristics and mtDNA differences: western North Atlantic, Iceland, northern Norway, and British Isles and North Sea.

Food and Feeding. The White-beaked Dolphin prefers to feed on various mesopelagic, schooling fish species from the families Clupeidae and Gadidae , including Atlantic herring ( Clupea harengus), Atlantic cod ( Gadus morhua), haddock ( Melanogrammus aeglefinus), poor-cod ( Trisopterus minutus and 1. luscus), whiting ( Merlangius merlangus), capelin (Mallotus villosus), and European hake ( Merluccius merluccius). They may also feed on cephalopods and benthic crustaceans. Foraging occurs in groups, with individuals spaced along a broad front to surround prey. These groups will also cooperatively herd schools offish into tight balls against the water’s surface to facilitate prey capture.

Breeding. Mating of White-beaked Dolphins is most frequent in May-September, and breeding peaks in July-August. Gestation is c.11 months. Females mature sexually at 8:7 years and males at 11-6 years; maximum documented age is 37 years.

Activity patterns. The White-beaked Dolphin may occasionally bow-ride and is known to be aerially active. They typically travel at speeds of 6-12 km/h but can swim at up to 30 km/h. Little is known about diving behavior, but data from a single tagged individual suggest that dives may last at least 78 seconds.

Movements, Home range and Social organization. Groups of White-beaked Dolphins generally consist of less than 50 individuals, but groups of several hundred and even more than a thousand have been reported. Larger groups tend to be observed in more offshore waters. In Icelandic waters, average group size is nine individuals; it is 4-6 individuals in Danish waters. Little is known of social organization or association patterns, but somestudies have suggested group segregation by sex and age classes. While feeding, White-beaked Dolphins may aggregate with other cetacean species, including the Fin Whale (Balaenoptera physalus), the Humpback Whale (Megaptera novaeangliae), the Sei Whale (Balaenoptera borealis ), pilot whales ( Globicephala spp. ), the Killer Whale ( Orcinus orca ), bottlenose dolphins ( Tursiops spp. ), the Atlantic White-sided Dolphin ( L. acutus ), and common dolphins ( Delphinus spp. ).

Status and Conservation. CITES Appendix II. Classified as Least Concern on The IUCN Red List. There are currently no estimates of total abundance or population trends of the White-beaked Dolphin, but there are likely more than 100,000 individuals throughout its distribution. Differences in skull morphology between populations from the Labrador Shelf and around Scotland suggest that the White-beaked Dolphin may have identifiable stocks. A study of genetic diversity also distinguished populations in the northern Norway and Scottish North Sea. There are ¢.7856 individuals in the North Sea, ¢.22,700 individuals on the European Atlantic continental shelf, and ¢.2000 individuals in near-shore eastern Canada, including the Bay of Fundy and Gulf of Saint Lawrence. The White-beaked Dolphin has been hunted opportunistically in Norway, Faroe Islands, Greenland, and Labrador, Canada, mostly for human consumption. About 366 White-beaked Dolphins were taken per year off Labrador in the 1980s (from twelve monitored harbors), but direct catch, which still occurs only in south-western Greenland, does not appear to be a major threat. The White-beaked Dolphin is incidentally caught in gillnets, cod traps, and trawl fisheries throughout its distribution, and catch rates are likely underreported in Canadian waters. Nevertheless, incidental catch in most areasis relatively rare and does not appear to be a major threat. The White-beaked Dolphin has an unusually highfrequency hearing threshold making it one of the most hearing-sensitive cetaceans, which could mean that it is especially vulnerable to noise disturbance from seismic exploration.

Bibliography. Banguera-Hinestroza et al. (2010), Gray (1846, 1850), Hammond et al. (2008a), Jansen et al. (2010), Jefferson et al. (2008), Kinze (2009), Lien et al. (2001), May-Collado & Agnarsson (2006), Nachtigall et al. (2008), Reeves, Smeenk, Kinze et al. (1999).

Figures

On following pages: 3. Peale’s Dolphin (Lagenorhynchus australis); 4. Hourglass Dolphin (Lagenorhynchus crucigen; 5. Pacific White-sided Dolphin (Lagenorhynchus obliquidens); 6. Dusky Dolphin (Lagenorhynchus obscurus); 7. Irrawaddy Dolphin (Orcaella brevirostris); 8. Australian Snubfin Dolphin (Orcaella heinsohni).

Distribution. Temperate to subarctic waters of the N Atlantic including S Davis Strait, Gulf of Saint Lawrence, Barents Sea, and North Sea, S to Cape Cod (USA) in the E and the coasts of N France in the W. Extralimital sightings in the Baltic Sea, Bay of Biscay, and Iberian Peninsula.