White-beaked Dolphin

Classification

Class: Mammalia
Order: Cetacea
Suborder: Odontoceti
Family: Delphinidae
Genus: Lagenorhynchus
Species: albirostris
Common Names: White-beaked Dolphin, white-nosed dolphin, squidhound
Irish Name: An deilf shocbhán
 

Key Identification Features

Max. adult body length/weight: 3.2m / 275kg
Average adult body length/weight 2.7m / 200kg
Average length/weight of calf at birth: 1.2m / 40kg
Blow: None
Head: Short but distinct beak. Beak not always white or light grey, with animals in the south of the geographical range tending to have dark or even black beaks.
Dorsal Fin: Prominent dark dorsal fin, mid-way along the back. Relatively large and sickle shaped.
Colouration: Fin, flukes and flippers a uniform dark grey. Patchwork of white, light-grey, dark-grey, and black along the flanks. Usually dark from the forehead to the trailing edge of the dorsal fin.
Markings: A distinctive white or pale-grey saddle behind the dorsal fin is characteristic of this species and useful in field identification. Two white patches are normally found on the flanks, one either side in front of the dorsal fin and the others on the flank behind the dorsal fin. These patches may merge into the pale saddle behind the dorsal fin.
 

Field Identification

The white-beak on the dolphin is diagnostic for this species; otherwise the pale saddle behind the dorsal fin and the two white patches on the flanks to the front and rear of the dorsal fin are characteristics to look for. These dolphins are strong swimmers, and often swim very energetically along the surface. They rarely bow ride anything but the largest of ships.
 

Species Similar in Appearance

Most likely to be confused with Atlantic white-sided dolphin or to a lesser extent the common dolphins. The best way to tell them apart is through the colouration on the flanks. White- sided dolphins have a characteristic yellow-ochre patch on the flanks well to the rear, while the common dolphin has a characteristic hourglass pattern.
 

Behaviour

A robust swimmer, white-beaked dolphins can often be seen swimming fast along the surface, creating waves and splashes. Although less agile than the common dolphin, they commonly breach clear of the water. White beaked dolphins are difficult to approach by boat although they sometimes bow ride, they seem to tire quickly of this activity. They may gather in huge schools of 1,500 or more but these schools fragment for mating and feeding.
 

Status and Distribution

White-beaked dolphins are widely distributed in the cool temperate and sub-Antarctic waters of the North Atlantic. Their distribution stretches from the edges of the Arctic ice pack in the Barents and Greenland seas to the warmer waters of the Bay of Biscay and Cape Cod. They use the northern area of their range in winter and migrate south in spring.

Common through most of their range, the white- beaked dolphin was once the focus of hunts in Iceland and Norway and along the Newfoundland and Labrador coasts. Recent attempts to renew this hunt in Norway have failed but Iceland has also expressed an interest in renewing their hunts. White-beaked dolphins are taken as by-catch in some gillnet, driftnet and trawl fisheries, however the extent of this is, as yet, unknown.

Dolphins from Newfoundland have been recorded with high levels of organochlorines and lead in their blubber and kidneys. Cetaceans in Irish waters have also been found to contain high levels of PCB's and Organochlorines. The effects of these high pollutant levels on the health of the population have not yet been determined.
 

Where and When Best Seen in Ireland

White-beaked dolphins are a pelagic (offshore) species but they may be often found further inshore than the Atlantic white-sided dolphin. They are generally found in waters off the Irish West Coast, along the shelf edge. They may also be seen of the southwest and south coasts but are rare in the shallower waters of the Irish Sea. They are found in Irish waters all year round.

The best area to find white-beaked dolphins is off the northwest coast. They are not that often reported stranded in Ireland.
 

Food and Feeding

White-beaked dolphins feed mainly on squid, octopus, benthic crustaceans, mackerel, cod, herring, whiting and capelin. Small schools of 6-30 animals gather to feed on schools of fish or squid, often hunting co-operatively.
 

Reproduction and Life Cycle

Max. life expectancy: Unknown
Average life expectancy: Unknown
Mating Occurs: July - October.
Season of birth: May – August in their Northern feeding grounds.
Gestation: About 10 Months.

White-beaked dolphins probably breed in Irish waters, as a late-stage pregnant female and a young calf have stranded on the coast in the past.
 

Social Structure

Schools may be as large as 1,500+ but smaller schools of 5-30 animals are the norm for feeding and breeding.
 

Conservation Issues

The number of white-beaked dolphins in Irish waters is unknown. They are caught in driftnets, gillnets and probably also in paired trawling and other pelagic trawls. Pollution is an unquantified threat as these animals are close to the top of their food chain.
 

Stranded Animals

The characteristic white patches in the flanks turn black soon after death, the white beak may be distinguished for some time after that but it too turns dark in time. The flippers are broad at the base with pointed ends and are dark in colour. The tail flukes are curved with a slight central notch and are also dark in colour. The tail- stock is relatively thick, with a strong ‘keel' above and below.

The lower jaw projects beyond the upper. They have 22-25 sharp, pointed teeth on either side of the upper and lower jaws. In some animals the number of teeth in the upper jaw may exceed the number in the lower by 2-3 teeth on both sides.
 

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