Can you tell the difference between a common seal and a grey seal? Genevieve Leaper shares some tips for identifying the different types of seal…
‘When angels fell, some fell on the land, some on the sea. The former are the faeries and the latter were often said to be the seals.’
While this old Orcadian view of seal origins is more poetic, modern science suggests the different types of seals evolved from land-dwelling carnivores and are more closely related to bears than angels.
Seals are so ubiquitous around our coasts that it’s easy to take them for granted. Most people probably don’t realise that Britain is the best place in Europe to see seals.
Types of seal in the UK
We may only have two species but the UK is home to more than a third of the common seals and almost all the grey seals in Europe. Indeed our 120,000 grey seals represent 40% of the world population.
There are a few ringed seals in the Baltic but to find more species you’d really need to head north to the Arctic. Grey seal distribution extends south to the Wadden Sea and northern France, but sailors further south are unlikely to see seals of any sort. The Mediterranean monk seal, the only species in southern Europe, is now very rare and endangered.
There are in fact only 18 species of true seals worldwide (not counting the recently extinct Caribbean Monk seal), mostly found in polar and temperate regions. Their close relatives the eared seals (sealions and fur seals), are not found in Europe, and their tusked cousin, the walrus, is (normally!) confined to the Arctic.
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Common seal spotting mistakes
With just two species, you’d think that identification wouldn’t be much of a problem, but it can be quite tricky to tell them apart. The names are somewhat misleading; the common seal is less common than the grey and both are generally grey in colour – though can be sandy, brown, or almost black.
The common seal’s alternative name of harbour seal is equally unhelpful. This species does tend to stay closer inshore but it’s the grey seals that sometimes take to hanging around fishing harbours waiting for a free handout.
The scientific names are slightly more descriptive, provided you can distinguish a ‘calf like seal’ (Phoca vitulina) from a ‘hooked-nosed sea-pig’ (Halichoerus grypus).
Some say that the grey seal has a face like a dog while a common seal looks more like a cat. Certainly the grey has a longer nose compared to the flatter face of a common seal but its Canadian name, Horsehead, is perhaps the most appropriate.
With his long convex nose, an adult bull grey seal is unmistakable, much larger and generally darker than either common seals or females of his own species. Young grey seals however can be extremely hard to distinguish from common seals.
Common seals can even be mistaken for other marine mammals at a distance; they can jump clear of the water like a dolphin.
If you hear seals ‘singing’ – a strange and rather mournful wailing – they’re grey seals. It is a haunting and melodic sound carrying over the water; closer to the effect is slightly spoilt by the punctuating snorts and grunts. Common seals are generally silent though I have heard a young pup calling plaintively for its mother.
Where to spot the two types of seal in the UK
Both species can be seen all round Britain and Ireland, but the largest numbers are found in Scotland. Anyone sailing the west coast of Scotland will have noticed on the chart a lot of rocks labelled Sgeir nan Ron, Ron being the Gaelic name for seal.
The Northern Isles and Hebrides are the main strongholds for the common seal, with large haul outs also in the Wash and Strangford Lough in Northern Ireland. They’re rather uncommon in southwest England but there are a few in the Solent and Chichester harbour.
Outside of Scotland, the largest grey seals colonies are found on North Sea coasts, such as the Farne Islands, Donna Nook in Lincolnshire and Blakeney Point in Norfolk. They also breed on Walney Island in the northwest and there are smaller colonies in Cornwall and Wales.
Unlike the truly marine whales and dolphins, seals spend time on land and are therefore mostly found in coastal waters. They are most conspicuous at their haul outs, where they often gather in large numbers; harder to spot when feeding at sea where they are more solitary and spend much of the time underwater.
Common seals mostly stay inshore, within 25 miles of their haul out, and even venture up rivers. If you see a seal in the middle of the North Sea it’s likely to be a grey seal. Satellite tracking has shown that they can travel hundreds of miles on foraging trips, even across to Norway.
Seals swim with their webbed hind feet. The front flippers are used for steering, also for hauling out and moving on land where the hind legs are useless. Although ungainly they can move surprisingly fast. They are well adapted to aquatic life with thick blubber and large lungs.
Seals forage on the seabed, regularly diving to 50m or more (grey seals can go much deeper) as well as in shallow, coastal waters. As well as large eyes for good underwater vision, they can detect their fish with their whiskers, which are sensitive to changes in water movements.
Both species eat a lot of sandeels, whitefish and flatfish. Common seals also like squid and octopus. At an anchorage on Jura I watched one diving repeatedly in the same spot near the rocky shore, surfacing only briefly to breathe.
As I watched the trail of bubbles I could only imagine what was going on underwater, maybe it was trying to extract an octopus from its hiding place – it must surely have been a very desirable prey to be worth so much effort.
Seals are curious and can be very playful, especially young greys. More than one diver has had their fins nibbled and they will follow my kayak for some distance. I hear heavy breathing astern but as soon as I turn to look, the seal vanishes with a splash.
Rowing a dinghy slowly can be a good way to get a close view. Some are bold enough to swim right up to a kayak or dinghy if you sit quietly – it sometimes seems like a group of youngsters are daring each other to approach ever closer.
One individual I got to know well just loved my kayak. Scarbelly (named for his most recognisable feature) liked to swim upside down under the kayak, rubbing his belly against the hull and caressing it with his flippers. He would have hauled out across the spraydeck if I’d let him.
Stand-up paddleboards could have been designed for seals and social media is full of stories of seals hauling themselves on board and apparently enjoying being taken for a ride. However friendly they appear it’s probably not really a good idea, seals have powerful jaws with formidable teeth.
I’m rather glad the big bulls keep their distance – these guys can weigh over 300kg – though I have seen adult grey seals playing with floating objects. One calm day my attention was caught by the danbuoy marking a creel (lobster pot) waving around violently.
As I watched the seal lunged out of the water again, grabbing the flag in its teeth to pull it down to the water where it let go, catapulting the pole upright. This was repeated several times before the seal turned its attention to the rope below the surface.
Although I never witnessed this behaviour again, I did notice the creel flags in this area looking particularly frayed. I wonder if the fisherman guessed why some of his flags wore out so quickly.
Seals are unpopular with many fishermen; some blame the seals for dwindling fish stocks and have retaliated by shooting them, which is now completely illegal.
But in one Hebridean anchorage, I have watched a fisherman lean over the side to feed a seal by hand. They obviously knew each other, the seal had been loitering for a while and swam to the boat as soon it arrived.
As elsewhere in the world, seals were once hunted for their skins as well as meat and oil. Common seal skins were used to make Scottish sporrans until the early 1980s. The main threats now include entanglement in discarded fishing gear, toxic chemicals and other marine pollution and disturbance at breeding sites.
They have no natural predators except killer whales but can suffer high mortality from disease such as phocine distemper virus. Storm Arwen last winter coincided with the grey seal breeding season and hundreds of pups are thought to have died at some colonies such as St Abb’s Head.
Breeding is one aspect of their lives where our two seals have very different strategies. Grey seal pups are born in autumn or winter. The timing of breeding varies considerably around the coast, from August and September in Cornwall and Wales to December in Scotland and the North Sea.
These are the white, fluffy-coated pups that look so adorable as they spend their first few weeks lying on the beach getting fat. Seal milk is very rich and pups gain weight quickly.
But once weaned, these youngsters get no more help from their mothers. Once they have moulted their white coats they must go to sea and fend for themselves. Males take no part in childcare; their interest is in the females who will be ready to mate soon after giving birth. Bulls will fight vigorously for females and many have the scars to show for it.
Watching one female with a late pup hauling out in a small cove, I was afraid I’d disturbed her when she turned to move along the shore instead of heading up the beach to her pup.
Then I realised that someone else had caught her attention. The bull hurried to meet her and they spent the next half hour in an amorous embrace at the water’s edge, the male gripping her neck with his teeth and both seemingly oblivious to the waves washing over them.
Seals are particularly vulnerable to disturbance when breeding, pups have been abandoned by mothers after people approaching too close to take selfies. Few people are out sailing when the majority of grey seals are pupping but common seals breeding in summer are more at risk from coastal sailors and other watersports.
They favour the same sort of sheltered places that make good anchorages, so please do give them a bit of space.
Common seal pups are born in June or July and as the females often give birth on intertidal rocks or sandbanks they have to be able to swim within a few hours and will then follow mother. Moulting takes place after the breeding season; autumn for common seals and winter or spring for greys.
This is another time when seals spend longer periods ashore. It may look like an easy life being a seal, lying around for hours on end, but they are not just being lazy. The moulting process uses a lot of energy and seals need to spend as much time as possible out of the water where they can maximise hair growth by increasing the blood supply to the skin.
Judging by the way they scratch themselves with their front flippers, moulting is also an itchy process.
Seals have long fascinated humans, quite beyond seeing them as a source of food and skins. Maybe it’s the habit of ‘bottling’, hanging upright in the water like a human swimmer, and staring back with those big soulful eyes, or because they come and go between sea and shore.
The Northern and Western Isles and Ireland abound with stories of the selkie folk. The selkies were seals in the water that became human on land. They had to carefully hide their skins when they came ashore, being unable to return to sea without.
The tales vary but often involve a cunning young man stealing the sealskin of a beautiful selkie-girl so she has no choice but to marry him. There was never a happy ending; the selkies always escaped back to sea when they could.
It’s probably impossible to recognise a selkie but just occasionally you might see a seal that is neither common nor grey.
Wally the Walrus may have grabbed the headlines with his tour of the British Isles last summer but walruses are by no means the only pinniped visitors from the arctic. Bearded, ringed, harp and hooded seals have all turned up on our shores.
Some years ago I spotted a seal with unusual colouring in deep water north of Shetland. Its head was dark on top and silvery underneath. I wouldn’t have been surprised to see a grey seal so far offshore, but this one looked much more like a common seal.
It was only when we saw another next day, with the same two-tone colouring, that I suspected these might be a different species altogether. They were in fact juvenile hooded seals, which are pelagic when young, wandering long distances, even as far as Portugal.
Shetland is the best place to find unusual pinnipeds but there have been records all along the east coast of Britain and harp and hooded seals have been seen in the southwest. The bearded seal, which would be better described as moustached, is probably the most distinctive, having very long whiskers with curly tips.
Wherever you’re sailing there are probably at least one of the two different types of seals not far away. So check to see if your anchorage is already occupied and keep an eye out for that sleek, round head in the water.
How to identify the two types of seal seen in the UK
|Grey seal||Common seal|
|Size||• Males larger than females
• Male 300kg, 200cm; Female 80kg, 180cm
|• Smaller, but adult size overlaps with young grey seals. male and female similar size
• 75-85kg, 135-145cm
|Coat colour||• Variable with large irregular blotches, older males often very dark||• Mottled with small spots in fairly uniform pattern. Darker after moulting fading to sandy brown|
|Head||• Long muzzle, top of head fairly flat or down-curving.
• Eyes halfway back on side of head.
• Nostrils parallel when closed (but appear V-shaped when open)
|• Shorter, more rounded face with more obvious forehead
• Eyes closer to front of head and more forward facing.
• V-shaped nostrils
|Pups||• White coated at birth, stay ashore for first 3 weeks||• Dark, can swim within hours of birth|
- Europe’s Sea Mammals: a field guide to the whales, dolphins, porpoises and seals – Robert Still, Hugh Harrop, Tim Stenton and Luis Dias (Princeton Wild guides)
- RSPB Spotlight Seals – Frances Dipper (Bloomsbury)
- Seals – Callan Duck (SNH Naturally Scottish series)
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What to do if you find an injured seal
Don’t approach the animal yourself. Call for advice and assistance:
- British Divers Marine Life Rescue hotline – 01825 765546
- RSPCA hotline (England & Wales) – 0300 1234 999
- SSPCA hotline (Scotland) – 0300 0999 999
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