Atlantic grey seals, north coast of Scotland
2. In the water
3. On land
Atlantic grey seals
11. Humans and seals
Atlantic greys, Cornwall
Common seal, Poole Harbour
Inevitably, the largest threat to seals comes from humans. Humans have hunted and eaten them since prehistory, as evidenced by bones (mostly from greys) in Mesolithic middens. During the nineteenth century, Orcadians would annually sail 60 km to Sule Skerry to ‘harvest’ hundreds of seals, which apparently made, ‘good ham’. Into the twentieth century, seal skins were utilised for small boats and blubber rendered down for lamp oil. Common seal skin was favoured for sporran-making until the 1980s.
Modern dangers include pollution, commercial fishing and climate change. The latter could adversely impact upon seals’ food supplies. The fishing industry hasn’t always favoured the conservation of seals, despite little evidence that they damage fish populations. Seals cause frustration through stealing bait from pots, and through damaging and infiltrating fish farms; the authors have found a dead seal with a shotgun wound, ashore beside a fish farm.
Viewing seals in the water, you will often find that they voluntarily approach you to investigate; greys generally come closer. Seals are understandably more wary of watchers whilst on shore. Try to approach from downwind, and keep a low profile. If the seals react to your presence in any way, you’re too close already; back off some distance and lie low to watch unobtrusively. Disturbance during the breeding season can cause genuine harm; if repeatedly disturbed into the water, cows (especially first-time mothers) can fail to recognise their pups and abandon them. Likewise, take particular care during the moult; their blood supplies are being directed to their skin to grow new hair; if forced to enter the water, they have to waste energy by having to shut off the blood supply and start all over again.
Atlantic greys, Isle of Anglesey
Common seals, Blakeney Point, Norfolk
Common seal pup during moult, Orkney Isles
In Shetland, commons are ‘tang fish’, tang meaning ‘seaweed’. As this indicates, commons are more disposed towards sheltered waters like east-facing coasts, or lochs and sandbanks in estuaries. Conversely, they spend more time in the water during winter than summer, reaching their heaviest weight whilst hunting in rougher conditions. Commons are found throughout Scotland, and the English North Sea coasts are a stronghold. Populations in the south-west and Wales are small.
It used to be thought that commons were somewhat anti-social and solitary. However, research has suggested that after some years of wandering, they ‘settle down’ in one place and form social bonds with others. Commons haul out in large groups, but like more personal space; they can be seen growling and swatting at others who impinge upon this. Greys are tolerated within these herds, although the reverse situation is unlikely. Some authorities claim that common herds are silent other than when breeding, but experience suggests that they ‘sing’ year-round!
Breeding is much more ‘synchronised’ than with greys, taking place in June/ July, countrywide. It’s not understood why, but cows leave their herds and find a separate haul-out nearby on which to give birth, either alone or with several other cows. Often the cow will use the same spot each year. Directly before giving birth, the cow will move away from others to calve alone. Common pups moult their lanugo in the uterus, being born yellow-brown. They weigh c10kg, but will double this within a month. The startling thing is that common pups are able to swim within hours, launching with their mothers when the tide comes in. This remarkable capability is possibly an evolutionary adaptation to cope with living on sandbanks. Within days (sometimes hours) the pup is able to dive, achieving ten minute dives within as many days. The pup is able to distinguish its mother’s voice and odour, but she mostly stays alongside, nuzzling and suckling it when ashore and even giving piggyback rides! The pup makes high-pitched calls to the cow, which in turn growls at seals venturing too close. The pup suckles for up to six weeks; being able to enter the sea with her pup, the cow loses less weight during this phase than a grey might.
You are unlikely to witness common seals mating, as it happens underwater. You might however see bulls flinging seaweed and sharply slapping the water, to attract a mate (youngsters can be seen ‘practising’ this behaviour during September). Directly prior, they call underwater once or twice, a bizarre and indescribable sound according to researchers who have heard it. Cows will respond within three weeks of pupping. There is competition involved; many bulls display wounds and scars from underwater fights with rivals.
Commons moult directly after breeding.
During 1988 and 2002, common seals were hit hard by phocine distemper virus (PDV); in the first outbreak, half of the North Sea population died. Only 10% of deaths were greys, although they also contracted the virus. Little is known about PDV, thought to have originated from domestic dogs.
Common seals, Orkney Islands
Common seal pup, Isle of Islay
Common seals, Isle of Islay
The Latin name for commons (phoca vitulina) means ‘plump calf’, if that helps! They do have more rounded heads and faces than greys, with a puppy-like visage and a snub nose. The mouth is under the nose, with long whiskers sticking out alongside V-shaped nostrils. The forehead angles upwards more steeply than the nose, and the eyes are closer to the nose than to the back of the head.
Commons have mottled coats with many small spots. Before moulting they are coloured muddy or sandy, but afterwards they are dark grey; they are sometimes called ‘black seals’ in Scotland.
Commons can be hard to ‘sex’. Bulls have thicker necks, but the best guide is to take a look at the belly of a basking common. You should see either an opening for a penis, or two nipples. However, both sexes can have protruding navels, which can be mistaken for penises.
Common seals, Isle of Foula, Shetland Isles
Common seals, Orkney Islands
Common seals phoca vitulina are also known as harbour seals, although greys are more likely to lurk in harbours! Commons are found worldwide, but the European subspecies Phoca vitulina vitulina numbers c83000. 35% of these are around Britain, with the majority (over 23500) in Scotland.
Common seal, Isle of Islay, Scotland
Atlantic greys, Cornwall
In Shetland, greys are known as ‘haaf fish’, meaning ‘deep sea fish’. This gives a good clue that they are at home hunting in exposed rough waters off the Atlantic coasts, based from remote shores or inaccessible islands. They are seemingly more sociable than commons, hauling out in closely packed herds. Herds moan and wail eerily, an unforgettable experience once heard.
Greys always return to the same spot to pup and mate. Calving takes place on beaches or inside caves above the spring high tide mark, as the pup will be ashore for up to a month. Newly-born pups sport a ‘lanugo’, a creamy coat of long fluffy fur. This colour is somewhat unhelpful camouflage; the Baltic and NW Atlantic populations of greys give birth on ice. They weigh c13 kg at birth, measuring under a metre. After three weeks, the pup will be of similar length but will have ballooned to 45 kg. Its new layer of blubber is a result of the fat-rich milk fed by its mother, who has stayed close throughout, losing up to half of her weight. The white coat now moults, replaced by short grey pelage. The cow now departs to find a bull to mate with. The abandoned pup starves ashore for up to a fortnight, before entering the water. Hence, grey pups are not ‘taught’ to swim and hunt; they simply figure it out.
Pups travel as far afield as Scandinavia or Brittany in their first years. Many are drowned in storms, but the remainder eventually return to their home shores and stay there.
As soon as pups are born, the cycle continues; bulls enter a rookery and go hungry to secure themselves a patch, viciously fighting others who infringe, and attempting to prevent cows that land (his ‘harem’) from leaving. Greys mate on land or in water. The bull grasps the cow from behind with his fore flippers, holding her neck with his teeth. A single bull will mate with up to ten cows, this being the end of his involvement.
Atlantic grey, Isles of Scilly
Atlantic greys, Cornwall
Atlantic grey, Isles of Scilly
Greys are the largest UK mammals found on land, twice the size of commons, but can still be tricky to distinguish. Their most distinctive characteristic is the long ‘roman’ nose, not unlike a horse’s muzzle; greys are known as ‘horseheads’ in Canada. There is no dip between a grey’s forehead and snout, their nostrils are parallel to one another, and they often display multiple chins.
A grey’s coat is darker on top than on the belly, camouflaging it from above and below. If the coat is uniformly dark with light patches and spots, it’s definitely a bull; the darker, the older. If the coat is more noticeably two-toned, with dark blotches on a lighter background, it’s definitely a cow. Got that? Unfortunately, old cows tend to be similar to bulls, and young bulls are easily mistaken for cows or even commons. All greys turn muddy brown during their moult, just like commons…
Atlantic greys in the Western Isles of Scotland
Atlantic grey seal, Western Isles of Scotland
The grey seal’s Latin name halichoerus grypus means, ‘hooked-nosed sea pig’. Greys are more common than common seals(!) around Britain, despite being rare internationally; we have 40% of the world population, c120000. 90% of these are in Scotland, where a staggering 40000 are born each year.
Atlantic grey seals in Yorkshire
Seals are the only British sea mammals which give birth ashore. Before and after the breeding season, they congregate sociably in herds (‘rookeries’) which can number hundreds. Their ‘pups’ are born singly on rocky or sandy shores, or even in caves or (in the Northern Isles) some distance inshore. Two or three weeks after giving birth, the ‘cows’ come into oestrus (i.e. are ‘on heat’) and mate with a ‘bull’. Like some other mammals (e.g. badgers), seals do not begin gestation directly after mating. The fertilised egg (the ‘blastocyst’) remains free-floating in the cow’s uterus, only attaching to the wall after three months. The embryo then gestates for nine months, meaning that seals have a year-long breeding cycle.
Seals tend to spend long periods of time ashore moulting after breeding and birth. They tend to moult successively; young seals first, followed by cows, then bulls.
|Atlantic Grey Seals||Common Seals|
|Size (Bulls)||200-245cm, 170-310 kg||145-185 cm, 55-130kg|
|Size (Cows)||180-220 cm, 105-186 kg.||135-175 cm, 45-87 kg|
|UK population (estimated)||120000||55000|
|Breeding season (calving and mating)||Isles of Scilly, Cornwall – late Aug-Sept
Wales – October
Scotland (successively; west coast and inner Hebrides, outer Hebrides, Northern Isles, east coast). – Sept-Dec
|Moulting||3-5 months after breeding, December to April||Month following breeding|
Atlantic grey seals, North Cornwall
Seals are best seen whilst ashore. They are less well adapted for land, shunting themselves on their bellies by flexing their hind quarters up behind and stretching their shoulders forwards… not unlike a caterpillar! They balance using fore flippers. Ungainly as this appears, they can certainly bounce along fast when required. Mostly, seals ashore just lounge around, sleeping, yawning, and scratching. One of our odder coastal sights is a seal flexed into ‘banana’ form, balanced atop a rock; this is done to keep their uninsulated flippers out of the rising tide, and hence delay having to move for as long as possible! Whilst seals clearly enjoy basking in the sun, their efficient insulation means that they have to swim periodically to expel heat.
Atlantic grey seal, Isles of Scilly
Like all seals, phocids live on both land and sea; but they are undoubtedly better adapted for the sea, able to range 100 km in a day. They can be seen swimming slowly on the surface, flexing their hind flippers from side to side and perhaps also paddling with their fore flippers. They achieve maximum speed underwater, streamlined by holding their fore flippers against their torpedo-shaped body.
Given that they are air-breathing creatures, seals are impressively adapted to survive underwater. Although they have a dense coverage of short fur extending to their flippers, insulation comes from ‘blubber’, a layer of thick fat. Before a seal dives, it fills its large lungs to collect oxygen. It then collapses them to expel all air, preventing problems from underwater pressure. The only remaining gas is stored in its stiff-sided trachea, for snorting seawater from its nostrils upon resurfacing. The seal closes its nostrils by contracting muscles, and finally submerges itself by rolling forward.
A typical dive lasts two to eight minutes, although over 30 is possible. The point of diving is to hunt food, so the seal needs to be active throughout. It survives by taking oxygen from haemoglobin in its large volume of blood, and from myoglobin in its muscles, a pigment retaining 40% more oxygen than haemoglobin. Seals possess an extraordinary ‘bi-modal’ metabolism; whilst underwater they are able to limit blood supply to vital organs only, and to slow heart rate from 80-120 beats per minute to 4-10. Seals actually burn up more energy whilst ‘resting’ ashore, than whilst hunting underwater.
What are seals doing down there? It’s possible to view their graceful underwater swimming and sharp turns from the surface, although they instinctively stay above camouflaging patches of weed and seabed. They hunt a range of fish largely dependent upon what is available, also being partial to octopus. Although they can dive to 250 metres, they mostly hunt along the inshore seabed. They are adapted for hunting in gloom or even total darkness by having large eyes, and hyper-sensitive whiskers which marine ecologists have suggested are as effective at tracking disturbances in the water as dolphin echolocation. Seals can also drink underwater, with kidneys adapted to process saltwater.
On surfacing, a seal breathes to exhale carbon dioxide. If its hunting was successful, it grips its fish with its clawed forepaws and tears into it with its teeth. It typically waits 10-20% of the time it has been underwater before diving again; when finished hunting, it needs several minutes for its surface heartbeat rate to return.
Photos show a common seal, taken at a seal sanctuary in Yorkshire.
Atlantic grey seal at Newquay, Cornwall.
Seals are found around all parts of our coast, but are most numerous in Scotland. In Orkney, legends abound of seals (known as ‘selkies’) temporarily shedding their skins to live among us in human form. What these stories perhaps reflect, is the anthropomorphic personalities and emotions that seals appear to exhibit when watched closely. Approached carefully, seals are not particularly shy of or adversely affected by the presence of humans. On the contrary, these charismatic creatures often show surprising curiosity in human activity, sitting in the water for hours on end, watching you watching them!
Seals (pinnipeds: fin-footed) evolved 26 million years ago from a common (possibly otter-like) ancestor. The c34 species of seal today fall into three families; otariids, or eared seals, including sea lions, odobaenids, or walruses, and phocids, or true seals. The two species of seals in Britain are both phocids; the common seal and the Atlantic grey seal. They share the ‘true seal’ characteristics of having small ear openings with no outside flaps and being unable to rotate their hind flippers or to raise themselves upright using their front flippers.
More to follow…