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Hilbre Island - LNR - Seals
In the waters around Hilbre Islands LNR can be found a number of different species of seals, below is a description of the two most frequent visitors to the islands. Please click on their names or photographs for further details on each species.
(Atlantic) Grey Seal (Halichoerus grypus)
Description: Adult male Grey Seals reach their maximum nose to tail length at about 11 years and are then 2.2m and weigh 220kg. Adult females are nearly 15 years old when they reach their maximum length of approximately 1.8m, with a weight of 150kg, though all weights do vary between individuals. They live a total of 15 - 30 years during which time they travel hundreds of thousand miles.
The coat colour of each seal varies and all shades of dark and light grey, brown and silver may be found. Both males and females have lighter bellies and darker backs with a varying degree of spotting. The sexes can be identified even when wet, by the distribution of the darker and lighter tones in colour. In the bulls (males) the darker tone, whether brown, black or grey, forms a continuous background, darker above and lighter below, upon which may be greater or less amounts of irregular spotting of the lighter tone.
In females it is the lighter tone that forms the background colour, upon which are spots and patches of darker colour.
The high, arched ‘Roman’ nose of the adult male Grey Seal is characteristic of the species. The adult female has a straight profile to the dorsal surface of the head. An anterior view of the nostrils of a Grey Seal shows them to be more nearly parallel to the Common Seal.
Distribution: The Grey Seal inhabits temperate and sub-arctic waters on either side of the North Atlantic, forming two distinct populations – the western population (Canadian waters) and eastern population (Britain, Iceland, the Baltic sea and Norway). A small number of individuals transfer between each population every couple of years, allowing the replenishment of fresh genetic stock to be exchanged, maintaining a broader genetic base for each population.
Around British and Irish waters the Grey Seal has increased in numbers. Two-thirds of the world population of Grey Seals (approx. 85000) live within our waters, with large breeding colonies around Wales, the Outer Hebrides, Farne Islands and Shetland. Outside the breeding season Grey Seals disperse over much of there range, with large numbers hauling out at places where no breeding can occur (e.g. The West Hoyle sandbanks near Hilbre Islands in the Dee Estuary).
Feeding: Grey Seals are fish eaters and not fussy at that, showing little preference for any particular species. There are records of at least 29 different species that have been consumed by Grey Seals. They favour bottom dwelling fish from depths of 70 metres or more, although pelagic fish are also eaten. Crustaceans and molluscs also make-up part of the Grey Seals diet.
Breeding: Grey Seals usually produce their pups in the colder months of the year. Round the coast of Britain the breeding (pupping) season is between the beginning of September and the middle of December, these times however vary with each breeding group. For example the colonies of Wales pup around September while the Scottish colonies pup during October and on the Farne Isles they pup during November. They have an active gestation of eight months and a total gestation period of about 350 days (c.11.5 months).
Neither bulls nor cows feed during the pupping and mating season and both sexes lose a lot of weight during this period. During the period of feeding at sea between about late November to mid-January, the seals regain this weight and undergo their annual moulting. The majority of females moult during early February, while the males moult later, peaking during mid-March. At this time they spend long periods hauled out, though not at the breeding sites.
Exploitation: In the UK, Grey Seals are protected under The Conservation of Seals Act 1970 from 1st September to 31st December. In Denmark the Grey Seal is protected all year from hunting, while in Norway they are protected in certain places and in Sweden professional licensed fishermen are permitted to hunt them.
Common (Harbour) Seal (Phoca vitulina spp. vitulina)
Description: Adult males are 1.5 - 1.8m nose to tail length and adult females 1.2 - 1.5m with a maximum weight of approximately 113kg. The colouration is very variable with a base colour of grey or brownish grey and the body covered with small black spots. There is no visible difference in the colouration of males and females. Common Seals can be differentiated from Grey Seals by their shorter, rounder head and their distinctive ‘V’ shaped nostril. Both species can occur within the same waters.
Distribution: Common Seals also known as Harbour/Spotted Seals are principally seen around estuaries and areas of exposed sandbanks. They can also be found on shingle beaches and on rocky shores that shelve gradually into the water allowing easy access. Common Seals occur on both sides of the North Atlantic and North Pacific Oceans.
The largest colony/group of Common Seals in the UK, possibly the world, is at the Wash. This area has a large expanse of shallow tidal sandbanks and is fed by four large tributaries. There are also smaller breeding colonies on the East coast of England – Blakeney, Norfolk; Scroby Sands, Norfolk and Thames Estuary. The total population of Common Seals within British waters is estimated to be between 20 - 40,000.
Feeding: The Common Seals diet consists primarily of fish species. There are records of 29 species of fish being eaten by Common Seals. Usually the commoner species of fish in the area are taken first with the seals diet varying according to the time of the year and the fish available. The pups after weaning eat shrimp, gradually progressing to adult food. In British waters Common Seals consume Flounder, Sole, Herring, Eel, Goby, Cod and Whiting. Sometimes squid, whelks, crabs and mussels are all taken.
Breeding: Common Seals have no obvious social organisation during the breeding season and appear to be quite promiscuous. Most births of pups occur at the end of June beginning of July. The pups are usually born on the shore, between tide marks, or on a sandbank between high tides. Each pup is around 85cm long and weighs about 11 - 12kg. Their coat is initially white but is shed upon birth to expose a short adult style coat allowing them to swim almost immediately.
The mother keeps watch over her pup for some time, helping it into the sea and will dive in tandem with them. Lactation lasts on the whole around four to six weeks and may take place in the water or on land.
Adults moult from the middle of August to the middle of September, after which the mating season commences with peak copulations at the end of September. During this time there is much splashing and energetic rolling in pairs in the water with snarls and yelps. Sexual maturity is reached in males at the age of six while females reach maturity at three to four.
Exploitation: The Common Seal is protected under The Conservation of Seals Act 1970, providing a close season for the seal from 1st June to 31st August. During this time it is unlawful to injure, kill or take a seal.