Other than a small population of Killer Whale Orcinus orca in the Outer Hebrides, the Grey Seal Halichoerus grypous is the largest living carnivore in the UK. The worldwide population of Grey Seal, which occurs in the eastern and western Atlantic Ocean and in the Baltic Sea, is thought to be in the range 290,000-300,000 animals (Seal Conservation Society (SCS), 2012). Approximately 38% (111,300) of the world’s population is thought to occur in UK waters, the majority of these (88%) breeding in Scotland, around the coasts of the Outer Hebrides and Orkney (Sea Mammal Research Unit (SMRU), 2011). In England the main breeding populations are centred around Donna Nook in Lincolnshire and the Farne Islands in Northumberland.
The Grey Seal is the larger of the two resident seal species with adult males measuring up to 2.7 metres in length and reaching weights over 300 kg. This species is distinctively different from the other resident species, the Harbour Seal Phoca vitulina, in having a long ‘roman’ nose and nostrils which are close together and vertical.
On the coast of northeast England Grey Seal pups are generally born in October and November. They have creamy-white fur (or ‘lanugo’), unlike Harbour Seal, which are born with a pelage which is something akin to that of the adult. Females only give birth to one pup but in October 2012 twins were reported on the Farne Islands for the first time (David Steel, pers. Com., 2012). Grey Seal pups are not able to swim soon after being born, unlike the Harbour Seal, which influences the choice of nursery site (or ‘rookery’) that Grey Seals make. Pups are nursed for approximately three weeks after which they are weaned and left to fend for themselves. They moult up to four weeks after being born and within two weeks of this they enter the sea, often dispersing widely from the colony (SCS, 2012) with one or two newly independent young occurring as far away as Teesmouth in December/January.
The main breeding populations in England are focused on the North Sea coast almost equally divided between the Farne Islands and Donna Nook in Lincolnshire. In 2010 there were 1,499 pups born on the Farnes compared to 1,417 at Donna Nook (Steel, 2011). It is thought that there are between 3,000-6,000 seals residing around the Farne Islands, a population that has been monitored since 1951, initially by members of the Natural History Society of Northumbria but then after 1971 by the National Trust when it appointed Peter Hawkey as the first Warden/Naturalist (Bonner and Hickling, 1971). In 1952, 496 pups were born on the Farnes including 20 which were stillborn (Hickling, 1962). In 2011, 1,555 pups were born there of which 1,077 are known to have been successful (Steel, 2012).
In spring, a smaller population of around 500 Grey Seals is to be found loafing around Coquet Island. The first pups recorded on Coquet Island were born in 2010, with three being monitored, but breeding was not repeated in 2011 (Paul Morrison, pers. comm., 2012).
The Tees estuary now supports a non-breeding population of 30-40 Grey Seals which are present throughout the year. This population has been monitored annually by the Industry Nature Conservation Association (INCA) since 1989 (Woods, 2012). The history of seal recolonisation of the Tees is discussed within the Harbour Seal account in this publication and so is not repeated here. The Grey Seal does not breed on the Tees because it requires birthing areas above the high water mark since the newborn pups are unable to swim. The Tees estuary is comprised of tidally inundated mudflats and sandflats that are more suited for the breeding population of Harbour Seal which occurs there (Woods, 2012).
In terms of other sightings, Grey Seals are known to occur in the River Tyne as far inland as Newburn some 15 miles up the Tyne, where they are noted to haul out on both the mudflats and the various concrete boat ramps in the Newburn bridge area (James Littlewood, pers. Comm., 2012). Sightings seem to coincide with the upstream movement of Salmon Salmo salar. This indicates that Grey and Harbour Seals in the North East will follow food many miles inland. Grey Seals have also been observed by INCA to exhibit such behaviour on the Tees, where they are regularly seen as singletons in the water at the Tees Barrage. This site is at the maximum extent of tidal flow on the Tees, some 16 km from the estuary. There are also occasional but regular sightings of Grey Seals hauling out on beaches in the Hartlepool and Redcar areas, which are situated on the northern and southern sides of the Tees estuary respectively.
The Farne Islands were one of first colonies in this country where seals were marked. Colour dyeing was first used on the Farnes in 1952 to obtain some idea of the colony size by counting the number of pups born (Hickling, 1962). In the 61 years of research to date there have been major fluctuations in the population. The 1,499 pup births on the Farnes in 2010 represented an 11% increase on the previous season and an almost 6% average increase on the period from 2005 to 2010 (SMRU, 2011). There have been a number of culls between 1962-1983 which killed a total number of 3,122 pups and 1,999 females. The short term effect of the culls was a decrease in pup production in the following few years and then stabilisation around the mid-1980s, with a gradual return to pre-1970 numbers. The short term decrease in the number of pups and females on the Farnes following culls could coincide with increases in nearby populations (such as Isle of May in eastern Scotland) as a result of females leaving the Farnes to avoid the culling. On days where higher numbers of seals were found hauling out on Lindisfarne less were found hauling out around the Farne Islands sites which suggests that this is a single population.
Other issues which have led to fluctuations in the population historically include the exploitation of seals for oil and meat from medieval times. In 1769 John Blackett leased the Farne Islands and he and his son William are known to have exploited seals unmercifully. In 1772, 72 pups were killed by William Blackett implying a population of approximately 250-300 animals (Selby, 1841). Just off Snook Point on the Farnes there was an area of water known as Bloody Bay, so called because of the slaughter of a large number of seals that had occurred there (Perry, 1946). This exploitation continued at apparently low (but unrecorded) levels until the middle of the 19th century when the seals were effectively given a level of protection by Archdeacon Charles Thorp, the lessee during the 1840s (Mennel and Perkins, 1864); however initial legislation to protect seals was not introduced until 1914 (Thompson and Duck, 2008). In UK waters the persecution of seals is currently managed by the Conservation of Seals Act (1970) which gives seals a limited amount of protection and places controls on the circumstances in which the killing of seals can occur. Aside from this activity there are recorded instances of seals coming to harm when in close proximity to fishing vessels. One memorable case was recorded in 1956 when a male Grey Seal lying out on the Longstone on the Farne Islands had been accidentally caught in a net. In freeing the trapped animal fishermen applied a rough cotton bandage to an injured part the seal’s neck which remained in place for at least two years. Another easily identified large bull seal in the Farne Islands area was seen in May 1959 with a rough “necklace” of jagged metal that was most likely to have been acquired whilst foraging around wreckage (Hickling, 1962).
In addition to anthropogenic effects there are occasional visits to the waters of northeast England by Killer Whale which is known to predate seals. On 7 September 1960 there was a larger than normal count of at least 2,200 seals on the Farne Islands but on 22 September the count had dropped to 917. There were no differences in tides between these counts and there were no visitors to cause disturbance but eventually a pod of Killer Whales was sighted in the area and thought to be to blame (Hickling, 1962).
Despite the threats faced by this species it does seem to be increasing in number. Latest estimates by the SMRU at the University of St Andrews suggest that the pup production rate increased by 6% in Orkney in 2010 and that this rate continues to “rise rapidly in the North Sea” (SMRU, 2011). This is in contrast to the Harbour Seal, which has suffered steep declines in its main breeding sites in Scotland in comparison with data from the 1990s (SMRU, 2011). The reasons for this are not yet fully understood, but it is postulated that the larger and more robust Grey Seal is out-competing the Harbour Seal for ever scarcer food reserves. Grey Seal has a similar diet to that of Harbour Seal and is also known to be able to forage further away from its home base. Grey Seal also seems to be much less susceptible to diseases such as Phocine Distemper Virus (PDV) which decimated the large Harbour Seal population of north Norfolk and south Lincolnshire (The Wash) in 1988 (Anderson, 1990) and to a lesser extent in 2002.
Written by Rhia McBain and Robert Woods (last updated Nov 12)