SEALS AROUND IRELAND
Ireland is home to two pinniped species, namely the harhour seal (Phoca vitulina) and the grey seal (Halichoerus grypus). These are members of the true seals (Phocidae). Contrasting to eared seals (Otariidae) – such as sea lions – they do not possess external ears. Their bodies are more streamlined adapting them perfectly to the marine environment. However, this also means that their hind flippers cannot rotate under their bodies, which makes movements on land extremely difficult. Sea lions can walk on land whereas true seals including the grey and harbour seal have to crawl along. Harbour seals look much like caterpillars doing this. Both of these have resident populations in Irish waters and breed along the Irish coastline. These two seal species are protected under both Irish and European legislation and Special Areas of Conservation (SACs) have been designated for both species. If you would like to know more on SACs around Ireland and which SACs include one or two of these seals, head over to the NPWS website for detailed information.
Cartoon showing one of the differences between eared and true seals (which include grey and harbour seals). With kind permission from Green Humour.
HARBOUR SEALS
In Ireland, the largest aggregations of harbour seals can be observed along the western seaboard where groups haul out in sheltered areas like estuaries and sand or mud flats. Adult harbour seals can reach a size of about 1.8m at a weight of about 130kg. Males tend to get slightly larger than females, but there is no easy to spot sexual dimorphism in this species.
Harbour seal with black coat and white rings. Tawin, Galway Bay Complex SAC
Harbour seal with light coat and dark spots. Lambay, Lambay Island SAC
Their coat has a unique pelage pattern, which is used to individually identify seals (we do this for the habitat part of the project).
Neonates already have their adult coat and can be individually identified. The coat is much darker though and will change colour over time (the pattern that is used to identify individuals stays the same).
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The pelage pattern can vary a lot and can include anything from an almost white coat with very dark spots to a black or dark brown coat displaying white rings. You can see this in the photographs on the left: The seal shown above has a black coat with white rings whereas the one imaged below has a very light coat and darker spots.
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The colour changes throughout the year and especially during the moult when seals shed their fur. This makes the pattern more difficult to recognize during that time though the underlying pattern will remain the same.
Harbour seals give birth to their young in June/July. The exact timing can vary between locations and seals generally give birth to a single offspring (twins are VERY rare in seals). Pups are able to swim from birth and do follow their mum into the water. They stay with their mother for the first 3-5 weeks of their lives after which time period they are fully weaned.
Mating starts during the breeding season and takes place underwater. Male harbor seals have their underwater territories and defend these against other males. Fights are common during this time and males might be seen with wounds. They make distinct underwater calls to attract females.
Following pupping season (June to July), it is time for the seals to moult (during the months of August and September). During this time, animals spend a lot of time hauled out ashore. This is also when ground counts are being carried out by NPWS as it is the time where most individuals are ashore and they are not as vulnerable as they would be during pupping. During winter, animals spent less time hauled out and more time foraging at sea.
GREY SEALS
The largest numbers of grey seals around Ireland occur on the western seaboard though there are also significant numbers in the east/southeast. Grey seals are dimorphic with adult females reaching about 2m and 100-150kg and adult males reaching up to 3m and 300kg. The snout is also different where males display a longer muzzle, which is wider at the end than in females. In adult males, the muzzle in convex whereas it is more flat in juveniles and females. You can see this in the photographs below where the male grey seal snout appears much more bulbous the female snout.
Male grey seal, front.
Male grey seal, profile.
Female grey seal, profile.
As in harbour seals, the pelage pattern is unique in grey seals and can be used to identify individuals. They generally appear dark grey or brown in colour and display darker and irregular spots and blotches. Studies have shown that the pattern is stable in young pups already and stays the same throughout their life. However, male grey seals darken with age so that adult males might not be recognisable.
Grey seals breed from September to December when they give birth to a single pup. The only currently confirmed case of twins for grey seals was observed in the UK in 2016. They were pups in rehabilitation named C3PO and R2D2 and genetic analysis confirmed their relatedness status. Pupping takes place in rookeries at remote areas such as offshore islands. Pups have their white lanugo fur which they shed during the first 6 weeks of their life. For this time, they cannot go into the water. Mum will stay with them during this period.
Mating takes place as soon as the pups are weaned when both males and females fast. Females fast for the duration of lactation and then start foraging whereas males fast for a longer period. Unlike harbour seals, mating takes place on terrestrial territories and males do not defend their territories. However, they might be observed trying to kill pups in a different territory to gain access to females. Males compete actively for females using gestures and vocalization, but fights are very rare.
Following this, individuals shed their fur during the annual moult (February to April). These seals migrate long distances outside of the pupping season, but they reassemble for the moult and haul out in large numbers. During summer, individuals spent more time foraging and are less often seen hauling out.