TRUE SEALS

Harbour Seal (Phoca vitulina)

Harbour Seals (Phoca vitulina) are sometimes known as Common Seals, but we prefer Harbour as the term Common may lead people to think the species are abundant and in no threat, which is not necessarily true. Aside from numerous threats to seals around the world, and reports of declining populations, at least 1 subspecies is classified as Endangered by the IUCN. However, the species are distributed widely globally. Estimated population size = 600,000.
P. vitulina are a medium sized true seal (males up to 2 m long/ 170 kg, females up to 1.7 m/ 130 kg) with relatively short front flippers and backward-facing hind flippers. They have a round head with V-shaped nostrils and no ear-flaps (as all true seals). Colouration can vary with distribution, ranging from a pale grey through to almost black, and even tan or reddish brown. Patterns also differ, with some coats all one colour, and others displaying darker speckles, spots, rings or splodges. These patterns are completely unique to the individual seal, in the same way as a human fingerprint, and as such are used by researchers to identify individuals.
Feeding behaviour:
The diet of P. vitulina fluctuates distributionally and seasonally, taking advantage of what is available opportunistically, and often predominantly relying on one or two species at a certain time of year. This tendency can lead them to come into conflict with fishermen in many parts of the world. They generally take on a wide variety of fish from surface waters, deeper water and the benthos, and many also feed on crustaceans, cephalopods and molluscs.
Breeding behaviour:
Sexual maturity – males 4-6 years old/ females 3-5 years old.
Courtship and mating usually occurs underwater promiscuously, with a tendency towards polygyny, but females haul out to give birth, and beaches are then defended by a dominant male who will mate with the hauled-out females. Gestation lasts around 9 months and pups are born from mid March to early September depending on location, though generally coinciding with warmer weather, and are fully waterproof, able to swim and fend for themselves immediately. Lactation continues for approximately 26 days, in which time the mother will routinely return to sea to feed, leaving the pup unattended or taking it into the water with her. The annual moult will then usually take place around late summer when pupping and mating are over. Yearlings, females and males begin to moult at different times in that order. Life expectancy for P. vitulina is 30-35 years.
There are widely recognised to be five subspecies of P. vitulina:
Eastern Pacific Harbour Seal (Phoca vitulina richardii)
Western Pacific Harbour Seal (Phoca vitulina stejnegeri)
Eastern Atlantic Harbour Seal (Phoca vitulina vitulina)
Western Atlantic Harbour Seal (Phoca vitulina concolor)
Ungava Seal (Phoca vitulina mellonae)
In the British Isles, our Harbour seals are the Eastern Atlantic subspecies (P. v. vitulina) and there are estimated to be between 110,000 and 140,000 individuals. Their range stretches across Northern Europe including Iceland, Svalbard and Scandinavia, down to the UK and Ireland, France, Germany, The Netherlands and Poland.

Photos: Debs Allbrook

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