Ribbon Seals (Histriophoca fasciata) are a striking looking, Arctic species of true seal inhabiting the northern Pacific Ocean and adjoining seas. ‘Histrio’ probably refers to the seal as a “stageplayer” whilst ‘fasciata’ means striped. With fairly large population estimates, the species is categorised as Least Concern. Estimated population size = 365,000.
H. fasciata are a medium sized seal (males ♂ up to 1.9 m long/ 148 kg, females ♀ up to 1.8 m/ 148 kg) with pointed fore flippers displaying different length digits, and long hind flippers that fan out broadly. Their heads are fairly small, round, and cat-like, with big, close-set eyes. The unique banding or ‘ribbon’ patterns that adorn the coat of H. fasciata are usually black and white or brown and white in males, and more brown and buff or brown and cream in females. The three light coloured bands encircle the head, the shoulders and fore flippers, and the lower abdomen. As mentioned, the colours of these are often less contrasting in females than in males, but they also vary widely in shape across individuals, and therefore are useful in identification.
Feeding behaviour:
The diet of H. fasciata is not well-studied, but samples taken from research subjects indicate that preferred prey might be a range of fish and invertebrates such as pollock, cod, octopus and squid. Small crustaceans seem to dominate in juvenile animals, suggesting that they graduate on to larger prey with age.
Breeding behaviour:
Sexual maturity – males ♂ 3-6 years old/ females ♀ 2-5 years old.
Solitary for most of the year, H. fasciata mate on ice in the spring in a suspected polygynous arrangement. Delayed implantation occurs, as in many seal species, for a duration of 2-3 months, before a 9 month gestation period. Pups are then born on the ice (generally offshore) during March-May. H. fasciata pups are born with fluffy white-grey coats which moult into blue-grey/silver coats around the time of weaning (approximately one month of age), when the pups are left to fend for themselves, living off their fat reserves while learning to feed and fend for themselves. The adults moult from May-July. Longevity is generally around 20-25 years, but can extend to 30 or so.
Studies have concluded that despite different populations of H. fasicata occurring in and around the North Pacific Ocean, these animals are not genetically distant enough to be classified as separate subspecies.
