Read how climate change is changing what leopard seals eat. Ringed seals build caves in the snow and create holes in the ice that give them access to the ocean. If that snow melts earlier than usual, it will put the animals at greater risk of predation from polar bears. All rights reserved. Male elephant seals battle each other for access to females. Common Name: Seals. Scientific Name: Pinnipedia.
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Environment As the EU targets emissions cuts, this country has a coal problem. The two blood temperatures participate in heat exchange and, therefore, the cold blood is warmed before re-entering the body core. Since walruses lack fur, the rushing blood to the extremities causes the skin to turn a rosy red hue.
Pinnipeds need to see both above and below the sea surface, a slight dilemma since good eyesight in either location requires very different adaptations. Terrestrial animals, including humans, rely on the cornea—the clear outer layer of the eye—to focus images using a property called refraction, a bending of light as it crosses through different materials.
As light travels through the air and enters the eye, it bends to the appropriate angle and creates a focused image on the retina.
Pinnipeds solve this issue with an especially round fisheye lens that refracts light appropriately underwater. Humans, on the other hand, have a flat lens. Having acute vision underwater means that on land a pinniped is nearsighted, especially in low light. When in bright sunlight, however, the pupil contracts, allowing only a pinhole for light to enter the eye.
This limited area decreases how effective the cornea and lens are at refracting light the mechanism that makes vision underwater clear and helps focus vision in air. Additionally, pinnipeds have a crystal structure in the back of the retina that reflects light back through the retina a second time, effectively doubling the amount of light captured by the eye. Pinnipeds gulp their food whole, which may be why they have a very limited sense of taste.
One study showed that a sea lion had an altered gene responsible for detecting sweetness, meaning they cannot taste sweets. They also lack umami taste receptors that detect savory taste.
Covering the faces of pinnipeds are whiskers called vibrissae. These hairs are extremely sensitive to touch, and can even detect sound vibrations.
Using their vibrissae, pinnipeds can determine the shape of an object placed in front of their face and detect extremely subtle water movement.
Pinnipeds rely on their vibrissae when hunting for food. When fish swim through the water their undulating fins leave a wake in the water and the vibrissae are sensitive enough to detect the trail back to the fish. As pinniped ancestors made the transition from land to sea they needed to adapt to a life both underwater and on land, and this includes hearing.
Hearing all comes down to the perception of vibrations, and underwater sound vibrations cause the entire skull to vibrate, not just the membranes in the ears. This is why sound underwater sounds garbled to humans. Pinnipeds have the extra challenge of needing to hear well in both air and water. They have massive ear bones and the ability to close the ear canal when underwater.
Pinnipeds scan their head side to side to help them pinpoint the source of a sound. Underwater, pinnipeds have no sense of smell, but on land scent plays a big part in day to day life. Scent is used as an alert mechanism when predators like humans are nearby and as a way for males to determine whether a female is ready to mate. Scent is also an important way for mothers and pups to bond.
Pinnipeds include the families Odobenidae walrus , Phocidae true seals , and Otariidae fur seals and sea lions. Today, there are 33 species. Some species exhibit sexual dimorphism, meaning the two sexes look distinctly different from one another. In many cases the male is also significantly larger than the females. Their closest relatives are the bears, weasels, racoons, skunks, and red pandas. Across the globe there are 19 species of seal.
Most are ocean dwellers, living in places spanning from the Arctic, to the tropics, to Antarctica. The Baikal seal, however, lives in a landlocked lake in the middle of Asia and is the only seal to live exclusively in fresh water.
The largest seal is the Southern elephant seal bigger than even the walrus and the smallest is the ringed seal. True seals lack ear flaps and propel themselves through the water with their hind flippers.
When on land they shimmy like a caterpillar. There are nine species of fur seals, which are close relatives of sea lions. They have visible ear flaps, strong front flippers, and the ability to walk on all four flippers when on land.
Males are larger than females—in some species they can be up to four times larger. While other pinnipeds rely on their blubber to keep warm, fur seals rely on a thick coat of fur. Sea lions and fur seals are distinguished from true seals by their comparably large front flippers, visible ear flaps, and ability to curl their back flippers under their body to walk on all fours. Sea lions are vocal, expressing themselves in loud barks. They are also social creatures, sometimes congregating in social groups of up to 1, individuals.
Unlike fur seals, sea lions do not have a significant fur coat and instead rely on blubber to stay warm. The walrus is the only remaining species of its genus; however, genetic studies show that there are two distinct subspecies of walrus, the Atlantic walrus and the Pacific walrus. Unlike all other pinnipeds, walruses have two canine tusks that protrude from their upper jaw. These tusks help them forage for clams and mussels in the muddy seafloor and are used to pull themselves up onto the ice when they surface.
Like sea lions, walruses curl their back flippers under their body to walk on all fours. The earliest ancestors of seals and sea lions were mammals that transitioned from life on land to life at sea. Around 36 million years ago, at the end of the Oligocene, the ocean began to cool, which caused major changes to ocean circulation. This led to an increase in nutrients throughout the ocean and enabled ocean life to thrive. Pinnipeds evolved from the ancestors of the musteloids which include everything from the red panda to skunks, badgers weasels, and raccoons.
One potential ancestor was Puijila, an otter-like creature with a long tail and webbed feet that likely lived by freshwater lakes about 24 million years ago. As both a land and water dweller, it used its strong leg muscles to paddle through the water. Since it likely walked on all four limbs, scientists consider Puijila to be a transition species that illustrates the evolution from land animal to marine animal.
Fully flippered pinnipeds did not emerge until roughly 17 million years ago off the coast of modern-day Washington and Oregon. Enaliarctos, a genus that includes five known species, is considered the group that all present-day pinnipeds descended from.
All four of their limbs were flippered, and they likely propelled themselves through the water using both the front and back flippers. Mating season means different things for different pinniped species.
For some, it means hauling out of the sea in massive rookeries on shore, while for others it can mean finding a sturdy ice floe. For the majority of pinnipeds, including all fur seals and sea lions, the mating season begins in spring when males come to shore to establish territories.
Only a select few males get the opportunity to mate, resulting in fierce competition over territory. In many species, males have evolved to be much larger than females, a characteristic called sexual dimorphism. Drawing on large reserves of blubber, males dutifully remain on land and guard their territory. Elephant seals can be especially brutal and fights will often draw blood. Such territoriality means bulls stay on land for up to three months to guard their territory and will even forgo feeding.
About a month after males come ashore the females begin to arrive. They congregate in the male territories in groups called harems. Upon her return they will need to reunite within the chaos of the rookery, and both smell and vocalizations help them do so.
Once bonding has occurred, the female prepares to mate again. She enters estrus, or heat, a reproductive state that advertises to the males that she is fertile. Females will mate with at least one of the males. Once the egg is fertilized it stops growing and remains in a dormant state for three months.
Part of the reason for this delay is that pinnipeds must give birth on land but fetuses take nine months to develop. The delay allows for birthing to align with the annual trip ashore. After females mate the next few months are dedicated to fattening the pups. In some species, mom will spend several days at sea foraging for food and then returning to feed her pup with milk. In other species, mom lives off her fat reserves and stays with her pup continuously until it is weaned. After a few months, the two return to the ocean and the pup learns how to forage for itself.
On the ice things are different. For species that mate on free floating ice floes, females are usually spread out over large distances, so males only have the opportunity to mate with one female per season. Ice is also unstable, and will break up differently from year to year, making the breeding season relatively short. Ringed seal pups are nursed for as little as three to six weeks before they become independent of their mothers. Unlike any other seals, ringed seals build snow lairs on the ice that help protect the pups from weather and predators.
In species that breed on pack ice, or stable ice attached to land, females may congregate in small colonies around a breathing hole. In this case, males sometimes will breed with multiple females in the same colony. When harp seals are born the mother spends about 12 days nursing the pup before she leaves in search of the males. The pup, a snowy white color, must quickly gain weight and learn how to swim or else drown when the ice pack breaks up.
Once their mothers have left the pups rely on the sea ice to rest. In recent years, like in , entire cohorts of seal pups have died when the ice broke up earlier than normal. Pups in all species need to gain weight quickly. Their kidneys are specially adapted to separating that salt and ridding it via the urine.
They pee, but sparsely. The urine is very concentrated and is sometimes saltier than the seawater. Should you visit their haul out area, you can often see small pits in the sand where seals have lain. This is where they peed and the sand has washed away. The penis opening of the male is relatively high up, just under the navel. With females, the opening is much closer to the tail. Seals have hair to prevent dehydration and damage when on land. The short hair also helps to prevent the cold seawater reaching their skin as quickly.
They molt every year. Harbor seals get a new coat in the summer, grey seals in March-April. In this period, they like to stay as dry as possible to allow the molting process to take place as quickly as possible. When it is very cold or the seals need to flee a lot into the cold water, the molting process is slowed down.
The coldness closes the blood flow to the skin. The process decelerates when there is a lack of blood in the skin. That is why it is very important that seals are able to rest in peace on the sandbanks during the molting process. Seals give birth on dry land. Harbor seals are born in the summer months, grey seals in the winter.
That is why grey seal pups have a thick winter coat. They are very adorable with their long white hair but it is also a bit awkward. The first few weeks of their life, grey seal pups remain on land. The mother returns regularly to nurse, which they do for an average of three to four weeks.
They are usually 10 kilos at birth and 40 kilos when they stop nursing. When their mother abandons them, the young seals must teach themselves that fish is edible and how to catch them.
The number of seals in the Wadden Sea region is well documented. Of the seals that inhabit the international wadden region Netherlands, Germany and Denmark , the large majority are harbor seals, numbering around 40, in adults and pups. However, harbour seals also inhabit other waters.
In the North Sea area, they are found around the Scottish islands, in the Wash, along the English, French and Belgium coasts, in the Danish Skagerrak and along the southern coast of Norway. Grey seals are found primarily around the Scottish islands, along the British east coast and in Cornwall. In December , there was even a young seal seen in the Thames beyond London.
In the Dutch Wadden Sea, a colony of grey seals was established in the s. Since then, it has expanded into the largest colony in the entire Wadden Sea. In the Dutch Wadden Sea alone, a total of grey seals were counted in the winter of The largest groups are located west of Terschelling, but small groups or individuals are sometimes seen elsewhere. The German islands of Helgoland and Amrum have colonies, numbering more than a hundred animals.
Satellite observations of seals with transmitters show that grey seals from the Wadden Sea can wander over the entire North Sea, and even swim from the Wadden Sea all the way to Scotland and back. Seals can also survive in fresh water. They used to swim regularly upriver. Nevertheless, it still happens. Seals are regularly spotted in the IJsselmeer.
They probably entered through the sluices by the Afsluitdijk Closure Dike. In , a seal was hit by a car while hobbling over the Afsluitdijk.
In addition to the harbour seal and the grey seal, both indigenous to the southern North Sea, an occasional arctic seal species will wander into these regions. For example, ringed seals from the northern Baltic Sea and even harp seals are sometimes reported. In , there was a small invasion of harp seals in the southern North Sea, caused by a lack of food in the Barents Sea. Beaching of hooded seals have been reported but are much rarer. In , several hooded seals washed ashore on the coasts of France, Belgium and the Netherlands.
There was also the unique event of a stranding of a female bearded seal on 27 June in the harbor of Yerseke in Zeeland. Other strandings include six individual walrus beachings in the 20th century, the last one on Ameland in January Seals were heavily hunted in the North Sea region in the past.
They were considered pests. They damaged fishing nets and snatched fish away from the fishermen. Hunters received premiums for every seal shot.
Despite the fact that hunting seals in the Wadden and North Seas ended more than 40 years ago and the seal population has grown, they are still threatened. The biggest threat facing seals nowadays is the flow of polluting waste materials from land to sea and from discharges and accidents at sea.
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