Seals are fin-footed creatures who are also a part of a superfamily of the Carnivora order. Research has revealed that seals or pinnipeds are descendants of a bear-like ancestor that roamed the earth 23 million years ago. They have slender and sleek bodies that are shaped like barrels. They spend most of their lives within the aquatic habitat they inhabit. They have short and wide flippers. The smallest seal on record is the Galapagos seal that weighs nearly 30 kg, while the largest on record is the southern bull elephant seal that weighs more than 2,000 kg.
The seals who have ears are also referred to as 'walking seals', and include the fur seals and the sea lions. Walking seals can move on all fours on land, and are social animals that put their rear flippers to optimum use while covering terrestrial habitats. The larger fore-flippers enable maneuverability expertise in water, but it is their dog-like snouts that make them distinctly different from their cousins, the true seals. While sea lions are generally larger than fur seals, recent genetic evidence highlights a close relationship between the two.
The 'true seals' are the ones without ears. They are also referred to as phocids. They are the most diverse pinnipeds that are distinctly different because of their streamlined snouts. They live most of their lives in the water and their well-developed rear flippers make them swimming experts. These aquatically-adapted phocids flaunt undulating body movements while swimming. Their physiological adaptations through evolution gear them for deep and long distance migration. They look very clumsy on land, wobbling from side to side, wriggling their front flippers and stomach muscles.
The exclusive seal family species is that of the walrus, the only surviving member of the odobenidae family of seals. Walruses are distinguished by their tusks and bulk that can sometimes exceed 2000 kg. They display features that are a perfect blend of those displayed by the walking seals and true seals. They not only have the ability to turn their rear flippers forward, but also display whole-body movements while swimming. Walruses do not have external ears and feed on clams and benthic invertebrates. They feed well on mollusks and adopt a unique squirt and suck method while feeding.
Seals have short limbs that have evolved into flippers with time. Their fingers and toes are 'woven' or bound together by skin, with claws on the front or back flippers. The reason for the small size of their flippers springs from the fact that the density of water is more than that of air. These pinnipeds are weightless when in water, and this enables them to remain still within and perform all the feats that they do to entertain large numbers of onlookers. They conserve oxygen longer underwater and are able to resist more pain and fatigue than other mammals.
They have a thick layer of blubber under their skin which serves a dual purpose. It keeps the mammals warm in winter and provides buoyancy. Newborns have no blubber. They also trap the warmth and energy of the sun beneath their fur, in the underfur on the skin. They do shed their fur, which is also referred to as molting. They can see above and in the water; however, when diving, a membrane covers and protects their eyes. The nostrils of seals also close when they are diving and are underwater. The reproductive organs like the testicles in males and the mammary glands in females are located under the skin. They have whiskers that help them navigate. They are able to relate to direction and sound underwater, with the help of the sensors in their skull. These sensors absorb the sounds underwater and transmit the same to the brain. They feed on other marine creatures. The bulls breed several dozen females in a single season and have exclusive harems.
Seals are very fascinating creatures and studying them is a lot of fun. Their peculiar habits make them very unique animals indeed.