White-Beaked Dolphin | cornwallmammalgroup

White-Beaked dolphin-(Lagenorhynchus albirostris)

Order: Cetacea, Cornish Name: Morhogh

Recognition:

A male white-beaked dolphin that stranded at St. Mawes in 2010 was thought to have been injured in commercial fishing nets. This was only the ninth white-beaked dolphin animal to be recorded by the strandings network.

Cornish Tales

The white-beaked dolphin is a large, stout member of the dolphin family. The streamlined, torpedo shaped body can reach lengths of up to 3.1 m and weights of up to 350 kg when fully grown. Its body is comparatively robust, with a short beak protruding slightly as the forehead (or melon) tapers down towards it. The colouration and patterning of the body is variable, but generally the back and flanks are dark grey, with the underside and beak being generally white. The beak may be blotched or spotted with grey. Behind the dorsal fin is a distinctive pale grey or white saddle extending down the flanks, this is less obvious in younger animals. There is also an irregularly shaped, light grey or white, streak running from above the eye towards the tail stock, where there can sometimes also be light grey patches. The black and white pattern is distinctive, although it fades in stranded animals. Despite the name, the beak may be dark on top or it may be all white, in any case, it is not always readily seen in swimming animals. The centrally placed dorsal fin is typically sickle-shaped (falcate) and is tall relative to the size of the animal, while the pectoral fins are swept back and pointed.

Ecology and behaviour

White-beaked dolphins tend to be found in deeper water so they are rarely seen close to shore where they can be studied in more detail.

Not enough is known about this dolphin to make an accurate estimate of life expectancy but they are thought to live for thirty years or more. Although first identified in 1846, this species is still poorly studied. Reliable estimates of age and size at maturity, and gestation period, are not yet available but it is thought that pregnancy lasts 10 to 11 months. The breeding season seems to be sometime between May to September, with most calves born in late spring. Newborns are approximately 1.1 m long at birth. Mostly this dolphin is found in groups of less than 10 individuals but occasionally pods of 500 animals have been seen. The groups may be separated by gender and age, and they may mix with other dolphin and whale species. White-beaked dolphins feed on fish, squid and octopus and hunt for prey both in the water column and on the sea bed. White-beaked dolphins are known to hunt cooperatively in pods, swimming in line abreast, driving schools of prey fish towards the surface. Gannets and kittiwakes are often associated with feeding pods of white-beaked dolphins, taking advantage of the herded prey. A fast swimmer, the white-beaked dolphin can reach speeds of up to 30 km/hr in short bursts and is often seen ridingboats’ bow waves.

Orcas and the larger shark species are the white-beaked dolphin’s natural predators; otherwise human threats include bycatch and occasional drive hunting in Canada and the Faroe Islands. One other note worthy problem is when pack ice forms in Hudson Bay, Canada, where animals can become trapped without access to air to breathe, so are either crushed, suffocated or forced to live strand. Strandings of small groups are not uncommon.

Survey Methods:

Land-based surveys will be fairly unproductive in most UK locations. Boat-based surveys, such as those by Marinelife and Organisation Cetacea (ORCA) around Europe on vessels of opportunity, are more suited to finding this pelagic species.

Conservation:

The world population is perhaps 100,000 or more. A notable decrease has occurred on the western side of the Atlantic since the 1970s, but there has also been a potential increase on the other side of the ocean, so it is not thought that the species is particularly threatened. In the UK they are listed as a species protected against intentional harm and disturbance under the Wildlife and Countryside Act 1981. White-beaked dolphins are currently listed as ‘least concern’ in the IUCN Red List.

Did you know?:

Around the UK, the white-beaked dolphin is more commonly recorded further north, around the coast of Scotland and the northern North Sea, and is only rarely sighted from the south coast. However, recent survey work by various organisations have made several observations in summer of small groups off the South West coastline, particularly in Lyme Bay, Dorset, and to a lesser extent, near Land’s End, Cornwall. It is not yet known whether they are a year-round population or if this is a seasonal movement to the very edge of the southern limit of their known range.

Distribution:

In Cornwall the white-

beaked dolphin is

almost exclusively

recorded from the

south coast. It is a

species more likely to be found in the

northern and central North Sea and north to Greenland, and rarely further south than Britain. They are seldom, if ever, found in the Arctic Ocean.

Records:

2007-2012: 12

2002-2007: 15

Pre-2001: 31