TRUE SEALS

Grey Seal (Halichoerus grypus)

Do not be fooled by the name as the Grey Seal (Halichoerus grypus) may not always be grey, and its latin name literally translated means hook-nosed sea pig. H. grypus is found throughout the North Atlantic ocean where it is listed as a Least Concern species by the IUCN. Estimated population size = 600,000.
H. grypus are medium large true seals, noticeably bigger than the Harbour Seal (males up to 2.6 m long/ 400 kg, females up to 2 m/ 250 kg). They have a fairly distinctive ‘Roman’ nose which makes them look a bit like dogs, with two parallel nostrils that are set apart from each other. They also have backwards-facing hind flippers and relatively short fore flippers, with no ear flaps. The coat of H. grypus can be grey or silver, through to brownish red, and may often contain blotches of darker colour. Their pelage marking is distinctive even after moulting, meaning that each seal is individually recognisable. Pups are born with a white fluffy coat or lanugo which is shed at around 2-3 weeks of age.
Feeding behaviour:
H.grypus are generalist feeders, predating on different fish species depending on location and season. The diet of an individual usually comprises of just a few species, and certainly less than 10, and these are predominantly demersal or benthic, so found near the sea bed. There is also recent evidence that H. grypus have been predating on Harbour Porpoises (Phocoena phocoena) in the North Sea.
Breeding behaviour:
Sexual maturity – males 4-6 years old/ females 3-5 years old.
H. grypus are polygynous breeders with males mating with up to 10 females on the land, ice or sea. Males will fight to attempt to gain access and defend their right to mate with groups of hauled-out females. On successful fertilisation of the egg there is a delayed implantation of 3 months before the foetus will start to develop. It then takes a further 9 months to gestate, so pups are born during the winter (usually December to January but can begin as early as September and end as late as March depending on location). As such, H. grypus young are born with a white fluffy coat, or lanugo, for warmth. During weaning, which takes approximately 15-18 days, pups remain on land and do not enter the water. The rich, fatty milk provided means they put on between 25 and 45 kg during this period. By comparison, the mothers will lose a vast amount of weight as they do not always feed during lactation. Once the young have weaned they will be left to fend for themselves, remaining on land for a further 1-4 weeks before heading to sea to learn to feed. Moulting occurs towards the end of the pupping season, females before males, beginning early January, and in some places as late as April-May. Average life expectancy of H. grypus is around 35 years for females, 25 years for males.
H. grypus are broadly split into two subspecies to the east and west side of the Atlantic Ocean. New evidence has recently re-evaluated these:
Northwest Atlantic Grey Seal (Halichoerus grypus atlantica)
Northeast Atlantic Grey Seal (Halichoerus grypus grypus)
In the Baltic Sea there is a small population of H. grypus that are genetically different from the rest of the Northeast population. These are generally recognised as a subpopulation of H. g grypus rather than a separate subspecies, though recent evidence actually places them as the original line of Grey Seals.
The British Isles are a stronghold for H. g. grypus, with populations spreading from temperate France up to the subarctic waters of Iceland, northern Scandinavia, and Russia. Current estimates of numbers come in at around 132,000 in total.

Photos: Debs Allbrook

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