Seals are semiaquatic mammals with a sleek, barrel-like body and fins. Their winged fins make them part of category of animals known as pinnipeds. There are 3 different families in the pinnipeds group: phocidae (true seals), otaridae (fur seals and sea lions) and odobenidae (walrus). There are more than 30 species of seals ranging from 16 feet (5 meters) long to the smallest species being about four feet (1 meter) long.
Seals are carnivorous animals who dive under water for fish, crustaceans, penguins, and other marine creatures. Some of the creatures, like the leopard seal, will eat other species of seals. Seals have sensitive whiskers that help them to detect prey in murky waters. Whales and sharks are the main predators of seals.
The mammals spend most of their time in the water and can be found all over the world. When they are lazing on land for an increased period of time that means they are breeding, about to give birth, or molting. Seals molt, or shed their skin, about once a year. It can take up to six weeks for the molting period to be completed.
Other facts about seals
Some seals can hold their breath for nearly two hours underwater by conserving oxygen.
A seal has a clear membrane that covers its eyes underwater. In addition, its nostrils close and blood circulation to most of its organs is reduced while diving.
Seals make growls and grunts underwater. Females and pups often call to each other.
Seals are insulated from the cold by a thick layer of blubber.
A female seal, called a cow, gives birth to one pup about once a year on land. The pups are nursed between 4 days and 1 month.
Most mother seals don't eat themselves while nursing relying mainly on blubber stores for nutrition. After weaning her pup, she will have to regain her weight.
Some seal species have been hunted almost to extinction in some parts of the world. The Caribbean monk seal was declared extinct in 2008.
Recent evidence suggests that pinnipeds evolved from a bear-like ancestor about 23 million years ago. These ancestors were likely land animals that traveled to the water for food.
Seals can sleep underwater. They can even surface to breathe without waking up.