Seals are mammals that live in the ocean, also known as marine mammals. Together with the family of sea lions and the family of walruses they are placed in a special clade of marine mammals. This clade consists of so called pinnepeds (Pinnipedia).
Pinnipeds got their name from the shape of their flippers. These animals have very short flippers, but with very long fingers and toes. This makes it look as if they have fins.
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Seals do not spend all their life in the water? The land is where they rest, warm up, mate and birth their pups. That is why we call them semi-aquatic: spending a part of their lives on land and in the sea!
Sea lions and walruses have similar physiques and adaptations, so what makes seals stand out? First of all, seals’ hind flippers cannot be folded underneath their body to walk on. Sea lions and walruses are able do this, which it easier for them to "walk" on land.
Seals have to hobble on their bellies to move on land. The way in which seals move is also referred to as caterpillar-like motion.
Another difference between sea lions and seals are their ears. Sea lions have small external ear flaps. Seals don't have such visible ears, they have ear holes on the side of the head.
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That most seal species are larger than sea lions and walruses? The largest seal is the southern elephant seal (Mirounga leonina). Male southern elephants can weigh up to two tons!
Seals are strong swimmers. They have to be, as seals spend a lot of time in the water. In general seals can stay underwater for a longer period of time than sea lions and walruses. To hunt for food, some seal species must be able to dive very deep.
A seal has a special way of swimming. To speed up, seals swim with their hind flippers by holding them flat against each other and moving them quickly side to side. You could compare this to how fish swim. Fish also whip their tail to the side to move through the water. The front flippers of seals are a lot smaller than the back flippers. They also don't use it to move forward, but to steer.
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The northern elephant seal (Mirounga angustirostrisis a champion in deep diving? They have reached depths as great as 1500 meters. In these depths they hunt for prey such as squid and other deep sea animals. Northern elephant seals can hold their breath for a very long time: almost 2 hours!
Most seal species live a solitary lifestyle. This means that they prefer to do almost everything on their own. The only exception is during the mating season, because then the animals congregate in large numbers to birth pups and mate. When mating season is over, the seals moult together, after which they each go their separate ways.
You can see seals resting in groups on beaches and sandbars, but that does not mean that they like to be together. Because seals are less agile on land, they cannot run away from large predators. Therefore, when the seals are on land it is safer for them to be with other seals. Additionally, often times there is not enough space to lie far apart so they are “forced” to be closer than they would want to.
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There are two seal species living in the Netherlands? The common seal (Phoca vitulina) and the grey seal (Halichoerus grypus).