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White-beaked Dolphin

White-beaked Dolphin © John Carnell

The White-beaked Dolphin Lagenorhynchus albirostris is a large dolphin with adults measuring 2.5-2.8m in length. It has a beautiful pattern of grey, white and black, including a distinctive pale saddle behind the prominent dorsal fin and frequently, although not always, a prominent white beak (Carwardine, 1995). The patterning and dorsal fin structure of the species is considered by the author to give rise to many of the claims of Orca Orcinus orca in our region, and may have led to a misunderstanding of the abundance and distribution of that species.

White-beaked Dolphin has a more limited range than most other cetacean species present in UK waters, being found only in cool temperate and subarctic waters of the north Atlantic (Reid et al, 2003). The population in the eastern Atlantic is thought to be larger than that in the west, with a range extending from northern Norway and Iceland to the British Isles and North Sea. Putting aside the well-studied population of White-beaked Dolphins in Lyme Bay, Dorset, the animals present off the North East coast are near the southern limit of the species’ range and potentially more susceptible to habitat changes due to increased sea surface temperature. Abundance in the North Sea has been estimated through the SCANS II survey in 2005 which gave an estimated population of 10,562 for the central and northern North Sea (Small Cetaceans in the European Atlantic and North Sea (SCANS) II, 2008). Recent collation of sightings data indicates the species is declining in the southern half of its range linked to sea surface temperature rise and the spread of Common Dolphin Delphinus delphis into these waters. Water temperature has been shown to be the most important variable in habitat partitioning between these two species (MacLeod et al, 2008). Declines have been most apparent around Ireland, western Britain and in the southern North Sea (MacLeod et al, in prep.). Given these likely distribution changes, the central North Sea (which supports some of the coldest sea temperatures in the UK), may be a current and increasingly important stronghold. This is one of our least studied cetaceans. The main prey items are white fish including Whiting Merlangius merlangus, Cod Gadus morhua and Haddock Melanogrammus aeglefinus, with crustaceans also regularly consumed (Evans, 1992; Santos et al, 1994; Canning, 2007; Canning et al, 2008).

Recent reductions in fishing effort of selected white fish species in the region may have benefited the species by increasing the availability of food sources. Observations from charter vessels by the author in 2003 and 2005 led to the development of the North East Cetacean Project (NECP) in 2009, in order to study the abundance and distribution of White-beaked Dolphins off Northumberland.

Mennel and Perkins (1864) did not list this species as being present in our waters although Davis and Muir (in Foster-Smith, 2000) described it as “the most common dolphin in the region, but occurring mainly offshore”. The earliest dated record is of a skull seen in 1881, from a specimen captured off Berwick-upon-Tweed. Davis and Muir go on to list a further 49 records of 75 animals, mainly strandings, with very few sightings of live animals up to 1998 and a small handful of records of indeterminate dates and counts. This perhaps typifies the difficulty in recording cetaceans; our most common dolphin species still averaged less than one record per two years for the period from 1881-1998, although this account will describe subsequent research and targeted observations that perhaps bring us closer to an understanding of how frequently the species is present off our coast.

White-beaked Dolphin by Chris Bielby

A survey of local skippers undertaken during 2004/05 by Newcastle University (Stockill, 2006) indicated that White-beaked Dolphins were the most frequently sighted species, being present offshore all year round and seen on 50% of trips to sea. Some large groups were also reported including a group of 250 dolphins, 25 miles off Cullercoats, reported by fisherman Kevin Dickenson.

White-beaked Dolphins are regularly recorded off the coast of northeast England, chiefly during the summer months from June to September (although there is often a dip in sightings during August), with fewer sightings in the winter which is consistent with observations from Yorkshire and northeast Scotland(Brereton et al, 2010). Pods of 10-30 animals are typically observed close inshore from late June, in loose aggregations of small groups, often with calves and sub-adults (author’s observation). The only month for which there are no records of the species in our waters is February, so it seems certain that it is present off the North East coast throughout the year, although the abundance and distribution pattern is not yet understood and is the subject of ongoing research. The majority of current North East sightings of White-beaked Dolphin are obtained from naturalists recording at land-based watch points. Local fishermen have indicated that the Farne Deeps has long been a key wintering area for White-beaked Dolphin. As the area supports high concentrations of White-beaked Dolphin prey items (Rogers and Stocks, 2001), it does seem likely that the area is a key location for this species. The only difficulty has been attempting to verify this; our offshore deeper water areas are no place for the faint-hearted during the winter and regularly prove difficult to visit during the calmer weather and sea conditions of the summer months.

Casual sightings data compiled for the period 2003-2009 by NECP found 43 sightings of approximately 279 animals for Northumberland and North Tyneside, along with several sightings for South Tyneside and County Durham. This compares with the 50 records of 79 animals from 1881-1998, and is a better indication of presence and abundance. It seems unlikely that the species has undergone a 20-fold increase in numbers, and much more likely that it has simply been under-recorded in the past.

Systematic survey work during the winter of 2009/10 failed to produce any sightings of White-beaked Dolphin and the media seized on this as evidence of global warming, with a rise in sea surface temperature leading to the loss of this cold-water species from the North East. The distribution of the species in UK waters is strongly linked to water temperature, with a strong preference for water temperatures cooler than 13ºC (MacLeod et al, 2007, 2008). Inevitably just a few weeks after publication of the NECP report (Brereton et al, 2010), the author watched a pod of White-beaked Dolphins from the Northumberland coast and the summers of 2010 and 2011 proved remarkable for sightings. Offshore pelagic excursions organised by Northern Experience Wildlife Tours provided many local naturalists with their first experience of the species as dolphins were bow-riding and breaching persistently alongside the small charter vessel used for these trips. Ongoing research by NECP, including compilation of a photo-ID catalogue for the species in the North East’s waters, aims to give us a better understanding of the abundance and distribution of this enigmatic species off our coastline.

References

Written by Martin Kitching (last updated Nov 12)