- 1 About Seals
- 2 Seal Identification
- 3 Seals in Scotland
- 4 What’s special about seals?
- 5 The seal’s life cycle
- 6 Seals and humans
- 7 Watching seals
- 8 Seals and the law
- 9 Seal Facts
With their large, dark-coloured eyes and engaging canine-like faces, seals are appealing animals. They live everywhere throughout the world, from the solidified squanders of the polar districts, to the tropical seashores in Hawaii, and wherever in the middle. Like mutts, felines, whales, mice, and people, seals are well-evolved creatures – which implies that they are warm-blooded and suckle their young. A large number of years prior, the progenitors of seals moved from the land once more into the ocean and advanced extraordinary qualities to adjust to their condition. Their awkwardness ashore gives a false representation of their preeminent style when swimming submerged where they are talented trackers of fish and other marine prey. Seals have flippers rather than hands and feet, and they can plunge for as long as an hour to profundities of more than 200m and even down to 500m without surfacing for breath. They are additionally clever, and some have been prepared to see short sentences and to act in carnivals and zoos.
What are the seals?
Seals have a place with a gathering of creatures called pinnipeds. This signifies ‘winged-feet’ and alludes to their flippers, which are extraordinarily adjusted for life in the ocean. There are at least 33 species of pinniped world-wide, including seals, sea lions, fur seals and walruses. Seals are different from their cousins, the fur seals and sea lions, in a number of ways. Most noticeable is that while fur seals and sea lions can walk about on all fours, seals can only wriggle on their stomachs. Fur seals and sea lions also have ears, whereas seals’ ears are so small that they can only be seen when they are wet. The largest pinniped is the elephant seal, and big males can grow to 4–5 metres (13–16 feet) in length. The smallest is the Baikal seal, which reaches about 1.3 metres (4.3 feet) in length. Male seals are known as ‘bulls’ and female seals as cows’.
Which seals live around Scotland?
Two species of seal are permanent residents in Britain – the grey seal (Halichoerus grypus) and the common, or harbour, seal (Phoca vitulina). Both spend much of their time at sea but come ashore to breed and moult. They can often be seen basking peacefully on beaches, sandbanks or rocks, and, being curious creatures, sometimes swim up to boats to see what is going on.
Grey seal or common seal?
Grey and common seals often inhabit the same parts of the coastline. They can sometimes be difficult to tell apart, especially when they are wet, and you can only glimpse a head bobbing up and down in the water. But grey seals have a very distinctive face, and the scientific name – Halichoerus grypus – actually means ‘sea-pig with a hooked nose’. This ‘Roman nose’ is even more accentuated in males. Grey seals are also larger than common seals, and the males, in particular, tend to be a more uniform colour.
Grey seals are the biggest living flesh-eater in Britain with around 36 per cent of the total populace found around the UK coast. They likewise live around Iceland, northern Scandinavia and the Baltic Sea, and southeast Canada. Guys develop to about 2.3 meters (7.5 feet), while females are littler and normal 1.8 meters (5.9 feet) long. The name ‘dim’ seal is fairly deceptive since there is a ton of variety in shading from practically dark bulls to rich white dairy animals and the lovely satiny white hide of new-conceived puppies. Normally both genders have a lighter shading on their stomachs than on their backs.
Regular seals, now and then called ‘harbour seals’, are broadly disseminated over the northern pieces of the Atlantic and Pacific seas. Coat shading and example shift impressively between various areas. Basic seals around Scotland have alluring coats, mottled with spots and rings, and can be anything between dim dark coloured to pale dim white. Their backs are regularly darker than their stomachs and chests. Guys normal about 1.5 meters (4.9 feet) long, while females are somewhat littler, and normal 1.4 meters (4.6 feet). Their logical name – Phoca vitulina – signifies ‘seal calf’. There are five races of normal seal and the UK bolsters 41 per cent of the European race Phoca vitulina – likeness 6 per cent of the total populace.
Seals in Scotland
Where are they?
Seals invest the vast majority of the energy adrift and might swim a huge number of miles during their lives looking for nourishment. They come shorewards for three reasons: to breed, to shed, and to rest between angling endeavours.
There are a few zones specifically in Scotland where seals assemble every year to breed and to shed.
The most significant of these incorporate the Orkney and, to a lesser degree, the Shetland Islands, the Hebrides, including North Rona, and the Monach Isles, which is the second biggest reproducing settlement of dark seals on the planet. Seals are additionally conceived at certain destinations on the Scottish territory every year, for instance at the ocean gives in around Helmsdale and at Loch Eriboll.
Outside the reproducing and shedding seasons, seals pull out on seashores, sandbanks and rocks, either alone or in little gatherings, to rest between angling undertakings.
Both species can be seen all around Scotland on many of the offshore islands, along much of the west mainland coast and also on the east coast, in areas such as the Moray Firth, the Firth of Tay and the Isle of May. Because seals range widely in their search for food, single seals of either species might be spotted anywhere along the Scottish coastline.
Seals use a variety of habitats as pupping sites on land. Some use flat sandy beaches, like Shillay in the Outer Hebrides, while others use flat platforms of rock, like the coast near Muckle Greenholm in Orkney. Still others use grassy areas above the sea, like some parts of North Rona, or offshore sandbanks.
When can they be seen?
Grey and common seals do not breed or moult at the same time of year. Female and male grey seals begin to arrive at the main breeding beaches towards the middle of September, and pups are born from the end of September until mid-December. Mating occurs about three weeks after the female has given birth. Females moult between mid-January to late February, while males moult between mid-February and early April.
The annual cycle of common seals is earlier than that of grey seals. They begin to arrive at the breeding grounds in June, and most births take place at the end of June and the beginning of July. Mating takes place when a cow has finished (or almost finished) suckling her calf. Common seals moult in August and September.
How many Scottish seals are there?
British seal numbers are estimated regularly using a variety of different techniques. Aerial photographs can be taken, and the number of seals counted from the photograph – easier than trying to count seals moving around on a beach. Sometimes seals are counted using binoculars from a boat or from the ground.
The most recently developed method is to use helicopters fitted with a ‘thermal imaging’ camera. This camera is able to detect the warmth of a seal’s body and can estimate how many seals are within a given area.
These surveys have shown that in 1994 there were some 99,400 grey seals around the Scottish coast and islands and that the population is increasing at a rate of about 7 per cent a year. About 36 per cent of the world population of grey seals breeds around Britain, and the Scottish breeding grounds are therefore especially important.
There are far fewer common seals than grey seals around Scotland, and British common seals comprise only about 5 per cent of the total worldwide population. There is a minimum of 26,400 common seals around Scotland during the breeding season although this number may be much higher.
Occasional seal visitors to Scotland
Seals travel hundreds of miles in search of prey, and occasionally a seal might wander far away from its usual feeding areas. These include ringed and harp seals, and, more rarely, hooded and bearded seals.
Ringed seals are smaller than grey and common seals, and are characterised by a very distinctive pattern of light-coloured rings on a grey pelt. Their bellies are silvery-grey.
Harp seal adults have very distinctive pelts unlike grey or common seals. They are grey-white with dark faces and a ‘harp’-shaped band across the back. Females are slightly lighter, although there is considerable variation in the colour of both sexes.
Bearded seals are larger than grey and common seals and are greyish-brown. Their most distinctive feature is a wealth of white shiny whiskers that grow from the sides of their distinctly flattened snouts.
Hooded seals are grey, with black irregular patches which are larger towards the tail. Adult males have an amazing inflatable hood on their heads, which they blow up when excited or alarmed. In some males, the hood maybe twice the size of a football. These seals can also inflate part of their nasal tissues into a large red balloon.
What’s special about seals?
Seals are supremely adapted for living in the sea. Like other marine mammals such as whales and dolphins, they can dive to great depths for long periods of time in search of prey, their bodies are streamlined to move efficiently in water, and they have blubber to protect them against the cold. But unlike whales and dolphins, seals spend some time out of the sea. They give birth on land – their pups would drown if they did otherwise – and they shed their skin annually on land. Seals can also move about quite adequately, although rather inelegantly, on land.
Limbs and movement
A seal has much shorter limbs than most mammals: what appears to be the armpit and groin of a seal are, in fact, the equivalent of the wrist and the ankle. By comparison, the bones of their flippers are enormously long, and the skin between them forms a web which is used as a paddle to propel the seal along. They have long, sturdy claws on their front flippers which they use to help them move on land, especially when they need to grip onto rocks or ice.
When a seal swims quickly, it holds its front flippers tightly against its sides, and propels itself with its powerful hind flippers. Its lower body moves from side to side, rather like a fish, as it moves along. When the seal is swimming slowly, the front flippers are used as stabilisers and stick out to the sides.
On land, a seal moves with a ‘hitching’ action. It forces it weight onto its chest, and then stretches its back to swing its rear end forward. The weight is transferred to the pelvis, and the chest is thrown forward. It is an inefficient way to move, and has made them vulnerable to hunting by humans. On ice, however, the seals are far more limber. Ribbon seals and leopard seals, that live in the Arctic and the Antarctic respectively, can move faster than a human can run, by flailing their hind flippers vigorously.
Heat and cold
Most mammals need to maintain a body temperature of 37°C (98.6°F). The sea is much colder than this, and conducts heat away from a warm body much faster than air does. Seals have dealt with this in a number of ways. They have a hairy coat, which traps air and uses it as an extra insulating layer. However, when a seal dives, the pressure forces the air out of the fur, so this only works when the seal is on land or near the surface. Far more important is the layer of fatty tissue beneath the skin, called blubber.
Sometimes, seals are so well insulated from the cold, that they overheat. Seal watchers occasionally see the seals waving their flippers in the air when they are hauled out on the land. This is no idle movement. Flippers have a large peripheral blood supply that allows the heat to escape. The waving movement is to increase the heat loss and so cool the animal down. The inventive, intelligent seal often finds other ways of keeping cool, seeking the shade of a rock or cliff or lying in pools of water.
Sight: to be efficient underwater hunters, seals need to detect and catch prey. Since very little light penetrates at great depths, the eyes of seals are specially adapted to allow them to see underwater. The eyes are especially large – one of the endearing feature of pups – and the lens is structured to allow as much light in as possible. When on land, the eye is protected from bright sunlight by closing the pupil. Thus seals can see well both underwater and on land. Sight is probably more important on land than in the water, and anyone watching common seals will notice that they raise their heads regularly to look for danger.
Hearing: the ears of the seals are also adapted to allow them to hear underwater as well as on land. The bones of the middle ear are larger than in land mammals, and there are changes in the shape and size of other bones in the skull. Sensitivity to sound helps them to detect prey underwater. It has been suggested that seals echo-locate, like whales and bats. Common seals are known to make clicks and trills underwater. It could be, however, that they are simply talking to each other.
Touch: when water is especially dark or murky, seals cannot use their excellent eyesight to help catch their prey. They have, however, sensitive whiskers called ‘vibrissae’ that grow on either side of the snout, above the eyes, and on top of the nose and are thought to detect vibrations in the water caused by moving prey. There are cases of blind seals surviving for a number of years in the wild, suggesting that for fishing the whiskers are more important than sight.
Smell: a sense of smell does not work in water for seals. If you watch a seal, you will see that it closes its nostrils tightly before diving, to prevent seawater from irritating the delicate membranes in the nose. But the nose-bones in the seal are large and quite complex, suggesting that a sense of smell is important on land. As soon as a pup is born, it and its mother sniff at each other. Not only do they recognise each other by their individual call, but by their individual smell. Basking seals often raise their heads and sniff at the air.
Diving and feeding
Seals have been known to dive as deep as 4,100 metres (13,450 feet) and can remain submerged for up to an hour. Grey and common seals, however typically dive to a maximum depth of around 200 metres (655 feet), for periods of up to 15 minutes, although they can go deeper and for longer.
It is a pity that most people only see seals flopping about in their ungainly way on the shore. There is little that compares with the grace and speed of a swimming seal. Whether alone or in a group, the movements of a seal in its true environment are like an underwater ballet. It can swim at speeds of 20 knots (around 23 miles per hour) when it is pursuing its prey, although most of the time it cruises at about two or three knots.
Both grey and common seals eat a variety of prey – fish, shellfish, squid and octopus. They are opportunistic feeders, and will eat whatever is available, including cod, herring, flounder, sculpin, salmon, mackerel, sandeel, shrimp and whelk. Their fishy diet often brings them into conflict with Scottish fishermen. (Discussed under ‘Seals and Fishermen’)
The seal’s life cycle
At the onset of the breeding season, the hormone levels of male seals change. They become aggressive towards other males, and begin to seek out females. Meanwhile, in females, the uterus has developed a fluid-filled sack containing an egg. Hormonal changes begin to occur in the female, making her receptive to the advances made by males.
The success of the species depends upon the female being mated by the biggest and strongest male. If she becomes pregnant by a weakling, it is more likely her offspring will also be weak, and its chances of survival will be reduced. The large, powerful males arrive at the breeding grounds and begin to fight other males to station themselves on the beach. The breeding season, which may last several weeks, is one long, continuous battle to keep other males away. A bull cannot risk going to sea to feed, because if he does, he might not be able to re-establish himself.
When the cows are receptive, the bulls move in, aiming to mate with as many as possible. By remaining on shore, the bulls make sure that they do not overlook any cow in their area. Copulation can last for up to 45 minutes, although most are quicker than this. Most cows are mated several times. A grey seal bull lies to one side of the cow with a flipper draped across her. He might also hold her neck in his teeth. Common seal mating takes place in the water, and it is difficult to see how many times a female might be mated.
All seals need to moult their old skin and hair once a year. Hormone changes prompt the seal to go to the moulting grounds. Grey seals gather together in large, noisy groups at this time. Juvenile seals usually moult first, followed by females, and finally by adult males, although there is overlap in the coming and going. The moult might take as long as six weeks to complete, during which time the seals are often irritable and listless. Once their new hair has grown, they head out to sea to resume feeding.
Once the egg is fertilised, there is a delay for about three months before the foetus starts to develop. The foetus grows for about nine months, at which point the female instinctively returns to the breeding grounds. When she arrives, she spends some time choosing a suitable place. Birth is normally quick, but despite the pup being long and spindle-shaped breech births are quite common. As soon as the pup is born, the female spins around to sniff it and to call to it. The pup and the mother bond, learning each other’s smell and voices within a few minutes of the birth.
Pups are relatively helpless, and rely totally on their mother’s milk for the first few weeks. The milk is more than 50 per cent fat, and the pups grow very quickly, depositing a thick layer of blubber that will protect them from the cold and sustain them as they are learning to hunt for themselves. Grey seal mothers feed their pups with milk for 16 to 21 days, during which time the pup gains an average of 30 kg (66 lbs). During this period of intensive care, the mother might lose 65 kg (143 lbs) of her own body weight. When the female is forced to return to sea to feed, the pup might remain at the breeding ground for another 14 days or so before heading out to sea to forage for itself.
Common seals are different. The pups are less helpless than grey seal pups, and can swim with their mothers within a few hours. This may be an adaptation to avoid dangerous predators, like humans. Common seal pups are suckled for up to six weeks, twice as long as grey seal pups. This is because there is no need for the mothers to fast and remain with their pups all the time. They can return to sea to feed themselves between suckling bouts and so do not lose weight to the same extent as grey seal mothers.
Not all pups survive. Some get separated from their mothers before they have a chance to learn their smell and call. If the mother does not recognise her pup, she will not allow it to suckle from her. Others get trampled by bulls, or are orphaned. In a crowded breeding area, 15 per cent of the pups might die. But some pups are resourceful, and not only take the milk from their own mother, but from the mothers of other pups too.
The life of a seal
A female seal becomes pregnant for the first time when she is three to five years old (sometimes earlier in common seals), and gives birth to a pup a year later. Although twins are sometimes found in the wild, they are rare because it is difficult for a female to provide enough milk for two pups. After her pup is born and she has finished suckling it, she is mated by one or more of the dominant bulls present at the breeding site. She then returns to sea to feed and make up for the weight loss she has suffered while caring for her pup. Later she hauls out to shed her old coat and grow a new one, which usually takes around four weeks. When her new coat is ready, she returns to sea, hauling out occasionally near her feeding grounds. She heads back towards the breeding grounds when the pup that was conceived during the previous breeding season is ready to be born.
A grey seal male becomes sexually mature (that is, he is ready to mate) at about six years of age, although he is usually far too small to successfully compete with the dominant bulls, forcing him to prowl in the shallows, or fight his way onto a patch of land that no other bull wants until he is big and strong enough to be able to win his battles for a breeding territory. Most grey seals are more than 10 years of age before they can maintain a position on the breeding grounds long enough to mate.
Common seal males reach sexual maturity earlier than grey seals, and are ready to mate between three to six years of age. They are usually strong enough to mate when they are about six or seven. Once mating is over, the bulls return to sea to feed, hauling out a few weeks later to moult. Like females, they haul out occasionally to rest between fishing forays.
If they survive the dangers of being a pup, seals are relatively long-lived animals. Both species often live longer than 30 years and one female grey seal in the Shetland Islands was known to be 46 years old. Since many seals die at sea, it is difficult to know the major causes of death. Diseases caused by parasites, pollution, and drowning in fishing nets are some of the main reasons.
Seals and humans
Seals and fishermen
Seals and fishermen are seldom the best of friends. Fishermen claim that seals damage their business by eating fish that they might catch. It is, however, not that simple. Many of the fish taken by seals are non-commercial species or not of the correct size and seals are not the only predators.
Seals are also host to a large number of parasites, such as codworm, which is passed from the seals to the fish and back again as the larvae develop. This affects not only the quality of the infected fish which are of lower value, but it also affects the growth and survival rates of the fish.
Salmon fishing is an important Scottish Industry, and seal damage to the nets and to the catch was once a serious problem. In recent years, stronger nets have been used, specially designed so that seals cannot chew through them and attack the fish inside. Fishermen are allowed by law to shoot any seals that are attacking the nets, but only very few seals are killed each year as a result of this activity.
In many sealochs, salmon are reared in net cages. Although seals seldom break into them, if they do, the result is disastrous. Besides the fish that the seal eats or injures while feeding, thousands more might escape. In 1989, one fish farmer reported that a single seal had attacked his fish and he had lost 13,000 salmon (at a market price of £20 per fish). Fish farms often have an extra layer of thick anti-predator netting around the cages to keep seals (and otters) out. Attempts have also been made to frighten seals away by using sound recordings of killer whales. But seals have excellent hearing, and seem to be able to tell the difference between a real whale and a recording. Instead of scaring the seals away, the tapes may instead tell the seals that food is available.
In the relationship between seals and fishermen, fishermen are not always the victims. Seals often become entangled in the sturdy nylon nets, and if they cannot reach the surface for air, they will drown. Occasionally nets are lost. These are known as ‘ghost nets’ and continue to catch or entangle seals, cetaceans, fish and birds long after fishermen have written off their loss.
Seals like to play, and pieces of brightly coloured nylon from broken nets are irresistible toys. Often these tough materials become wrapped around a seal’s body, and cut into it as the seal grows. They can also impede a seal’s swimming, reducing its chances of survival because it cannot hunt properly.
Seals and hunting
Their thick layer of blubber makes seals an attractive quarry. In Scotland, subsistence crofters and farmers killed seals until very recently for the oil that could be taken from the blubber. The oil was used in lamps, as medication, and for softening leather. For many years, sporrans were made from sealskins.
This small-scale hunting had very little impact on the local seal populations. There was a balance between local Scottish hunters and the seals, in the same way as there was between the peoples of the Arctic and the seals. However, in other parts of the world, the commercial hunting which started in the 16th century and continued until the 1970s put an end to this balance. Seals stocks from the Antarctic to the Arctic, and almost everywhere in between, began to decline dramatically.
Environmental pressure groups, such as Greenpeace, began a campaign called ‘Save the Seals’. The emotive sight of big-eyed, white coated harp seals being clubbed to death for their fur resulted in a public outcry.
As a result, the European Community issued a ban on harp and hooded seal fur in 1983, effectively destroying the fur trade. Neither grey seals nor common seals are endangered species.
How to watch seals
You can see seals from vantage points overlooking their breeding or moulting grounds or from boats. During the breeding seasons, special seal-watching trips are often available. Seals are curious animals, and will often swim up to a boat to see what is happening. They can therefore be seen from very close quarters. Some important breeding areas are closed to tourists, or accessible only with a qualified guide.
You can find seals hauled out on beaches all along the Scottish coast. If you see a seal on a beach, do not go too close: if the seal is a pup, you might drive the mother away.
Dogs should not be taken near seal breeding and moulting grounds, and should not be allowed near seals hauled out on other beaches because they can frighten the seals. In the mad rush for the safety of the water, pups may be injured or even killed.
When to watch seals
The best time to see seals is when they are on shore to breed or moult. Scotland’s grey seals breed and pup September to mid December (peak pupping is October and November). They moult in June and July. Scotland’s common seals breed and pup between late January and early April (the peak pupping is February and March). They moult in August and September.
A word of warning
Seals are wild animals and they bite. Seal bites often become infected and are slow to heal. If a seal is seen on a beach, even if it appears to be dead, keep a safe distance. Seals often appear to be dead when they are only sleeping.
Seals and pollution
When toxic materials are discharged into the sea, ocean currents can disperse them over huge areas. For example, radioactive chemicals from England have been traced in the seas to the north of Russia. Some of these toxins enter the food chain at the level of plankton, and pass upwards through shellfish, fish, and ultimately seals at the top of the chain. These toxins include lead, mercury, cadmium, strontium, PCBs, and the insecticide DDT, all of which have been found in seals.
It is not known how the accumulation of these toxins in a seal’s body might affect it, but scientists believe that it may reduce immunity to certain diseases, or result in females producing fewer or sickly pups. It is possible that pollution may have been at least partly responsible for the large number of seal deaths from ‘phocine distemper virus’ in 1988–9. In Europe, 17,000 common seals died of this ‘seal plague’, including about 1,700 British seals.
Oil spills can also damage seals. Oil is an irritant that can affect eyes, noses, ears and throats, and inhaling the fumes can cause poisoning. Otters rely on their fur to keep them warm, and when the fur becomes matted with oil, they often die of hypothermia. Seals by contrast have blubber, and oil on their hair is only a minor problem. This explains why there were 4,000 otter deaths after the oil spill from the Exxon Valdez in Alaska in 1989, but only 18 seals were found dead. However, 80 per cent of the common seals in the area had oil on them, and many were seen to have ulcers, sores and breathing problems.
In January 1993, the MV Braer oil tanker ran aground in the Shetland Islands during a storm, leaking 85,000 tonnes of oil. Within 1.6 kilometres (one mile) of the spill was a popular grey seal haul out site. No seals appeared to have died as a result of the spill, although some appeared to be suffering from breathing problems which may have been caused by inhaling fumes.
Seals and the law
Grey seals were protected as early as 1914 when the Grey Seals Protection Act made it unlawful to kill seals between 1 October and 15 December each year, and never at Haskeir in the Hebrides. The Act was originally intended to protect seals for five years until the population had begun to increase, but it was then extended. Common seals were not protected, and in the 1960s, between 1,000 and 1,200 were killed each year in Scotland.
The Conservation of Seals Act 1970 made it unlawful to kill either grey or common seals during their breeding seasons (Grey seal close season – 1 September – 31 December; common seal close season – 1 June – 31 August) and limited the kinds of weapons that could be used to kill them at other times. In 1973, a special Order of the Conservation of Seals Act was passed which protects common seals in the Shetland Islands all year round.
There are 33 species of seal world-wide, two of which live around Britain.
Scotland is an important breeding area for grey seals.
The grey seal population is estimated to be increasing by seven per cent a year.
Neither grey seals nor common seals are an endangered species.
Grey seals are larger than common seals, and have a distinctive profile.
Unlike whales and dolphins, seals give birth on land.
Seals are insulated from the cold by a thick layer of blubber.
Grey seals mate on land, but common seals usually mate in water.
Seals have sensitive whiskers that help them to detect prey in murky waters.
As soon as a pup is born, its mother forms a bond with it by smelling and calling to it.
Grey seals have been known to live for 46 years.
Some seal species have been hunted almost to extinction in some parts of the world.
In 1988 phocine distemper virus killed about 33 per cent of all common seals in the North Sea.
Oil spills are thought to cause breathing problems in seals, as well as damage to ears, nose and throat.
Seals are wild animals if approached too closely they will bite.