Along with earwigs and walruses, seals are classified as pinnipeds - marine mammals that appeared on Earth about 24 million years ago. They share many anatomical features with earwigs, although they differ in lacking an auricle. Seals are also referred to as proper seals, earless seals, or, simply, seals. They live in the marine environment, and only one species has broken out of this classification - the Baikal seal, which inhabits the freshwater of Lake Baikal in Russia.
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Seals, or animals included in the seal family, are predatory marine mammals.
There are nineteen species of Phocidae (also called true seals or earless seals):
Mediterranean monk seal; Hawaiian monk seal; Caribbean monk seal, now believed to be extinct; Northern elephant seal; Southern elephant seal; Ross seal; Crabeater seal; Leopard seal; Weddel seal; Hooded seal; Bearded seal; Harbor seal; Spotted seal; Ringed seal; Baikal seal; Caspian seal; Harp seal; Ribbon seal; Grey seal.
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Seals are cold-loving animals; they live in circumpolar and temperate zone seas and oceans.
Although they spend most of their time in the water, they also need land to live, which is why they are found in coastal areas.
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Depending on the species, the body length of seals ranges from 1.17 to as much as 4.9 meters.
Their weight also varies greatly, with the smallest species weighing around 45 kilograms while the largest weighing as much as 2.4 tons.
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Their bodies are very streamlined and allow them to swim quickly and agilely.
They usually swim at about 10 km/h but can accelerate to about 30 km/h in a threatening situation or during hunting. Seals swim by making side-to-side body movements and are aided by their rear fins, which give them momentum. The front fins are used for steering.
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Although their fins give them speed in the water, seals move slowly and clumsily in the terrestrial environment.
The rear flipper is attached to the pelvic rim so that seals cannot point it downward and use it for walking.
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Ringed seals are the smallest of all species.
They inhabit the polar zones in the Arctic Sea, the coasts of Greenland, and Spitsbergen. An isolated population of 8,000 can also be found in the Baltic Sea. The species is under protection in Poland. Ringed seals reach 1.3 meters in length with a weight not exceeding 110 kilograms.
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The largest seal is the Southern elephant seal, also known as the Mirounga leonina.
It lives in Antarctic waters and reaches an incredible size. The average body length of the Southern elephant seal is 4.5 meters, while record-breaking individuals have reached up to 5.8 meters in length. The weight of these giants ranges from 1,500 to 3,000 kg, and record individuals reach up to 3,700 kg in body weight. They feed mainly on cephalopods and supplement this diet with fish.
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Seals do not have auricles.
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Seals breathe using their lungs but are adapted to holding their breath for long periods. Some species can stay submerged for up to 40 minutes.
It allows them to dive to considerable depths and stay underwater for long periods. When diving, the air from the lungs goes to the upper respiratory system, which is not as easily absorbed into the blood. This mechanism also protects seals from decompression sickness.
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Depending on the species, seals may use different foraging tactics.
Some are filter feeders and feed on krill, while others suck small prey into their mouths or grab larger prey and tear their skin. Some species, such as the Leopard seal, use all foraging strategies simultaneously.
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Unlike eared seals, seals do not bark for communication purposes.
Instead, they grunt and slap their fins against the water's surface.
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Although they live primarily in an aquatic environment, seals return to land or ice floes for reproduction.
During pregnancy, females feed heavily in the waters, accumulating fat to avoid having to return to the water after giving birth. The accumulated fat reserves allow these animals to feed their young. The only exception here is the Harbor seal, which, after giving birth, returns to the water from time to time to feed - a trait common for eared seals.
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When feeding their young, female seals do not eat anything and sometimes do not even drink.
Usually, the feeding areas are hundreds of kilometers away from the breeding sites. The seal's milk is highly nutritious and rich in fat, allowing the young to feed and grow quickly and the female to return to the feeding areas before she dies of hunger and thirst.
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Their mother's milk so well nourishes young seals that the mother leaves them before they reach adulthood.
They can survive without food for up to several months by burning stored fat before they are forced to go hunting.
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The oldest fossil specimens of seal representatives are from the early Miocene.
These animals appeared about 22 million years ago. Other fossil specimens dated 15 million years ago and inhabited the North Atlantic.
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Until recently, seals were thought to have evolved from sea lions and walruses. However, recent evidence seems to contradict this.
According to the latest research, seals appear to have descended from a common ancestor - a mammal called Enaliarctos, which inhabited Earth from 24 to 22 million years ago. The animal was related to weasels and bears.
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Three species of seals are found in the Baltic Sea.
They are the Gray seal, the Harbor seal, and the Ringed seal. The most numerous species is the Gray seal, whose population is estimated at approximately 30,000 individuals. The Harbor seal is the rarest, with an estimated 1,000 representatives.
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A seal sanctuary is a research center where seals are protected and studied.
The two most popular are the Fokarium in Hel, Poland, and Cornish Seal Sanctuary in Cornwall, United Kingdom.
