There are 35 different species of seals. However, only six types live in Antarctica. "The Antarctic seals belong to the group of marine mammals called Pinnipeds (fin-footed). This includes the Phocidae (true seals), Otariidae (fur seals and sea lions, or eared seals), and Odobenidae (walruses). In Antarctica, there is one eared seal - the Antarctic fur seal - and five true seals: southern elephant, Weddell, leopard, crabeater and Ross.
All seals are carnivorous, and except for the fact that their feet are flipper-like to accommodate an aquatic life style, they are very similar to the Carnivore order, which includes the cats, dogs, otters, bears, etc.
Many species of seals, including some of those found in Antarctica, migrate long distances during different seasons of the year. They gather on and around the pack ice and shorelines during summer months in order to breed. The females only give birth to one young. Because other seals disperse after the short breeding season, mating must take place soon after the females give birth.
The mothers' milk contains about 45% fat and 10% protein (compared to 4% and 2% respectively in cow's milk), and the seal pups grow very quickly. Most species are weaned in about two months. The males have little or nothing to do with the raising of their offspring.
While the fur seal and the true seal are fairly closely related, there are some important differences. Fur seals have external ears, their hind feet can be positioned beneath the body in order to walk or hop on land. By contrast, the true seal has no external ears, their hind limbs extend straight back in line with the body. Of all the differences, however, the most important is the composition of the fur. The fur seals are aptly named for their dense, luxurious coats. Their fur consists of two different types of hairs, guard hairs and under-fur, which are arranged in bundles. Each long guard hair is surrounded by up to 70 short under-fur hairs, which gives the animal a highly efficient protective layer of insulation against low temperatures. It also gives it a pelt which was once highly valued by people. True seals, rely primarily on a thick layer of subcutaneous oil-rich fat or blubber, to insulate their bodies from the intense cold. Their fur is not nearly so thick or luxurious. 
SOUTHERN ELEPHANT SEAL
The southern elephant seal has a large circumpolar range which includes not only the Antarctic mainland and islands, but most of the subantarctic islands as well. This is the largest species of seal in the world, surpassing even the walrus in size. The males grow to 20 feet in length and can weigh as much as 4 tons. Females, though large, are much smaller than the males and grow to about 12 feet in length and 1 ton.
WEDDELL SEAL
This is the most southerly of the seals - and indeed the most southerly of all mammals - breeding as far sough as 78 degrees South. It is almost always found within sight of land in both summer and winter. The species was not discovered until 1823 when Captain James Weddell captured six specimens during his voyage to the South Pole.
CRABEATER SEAL
This is the most abundant seal in the world, totalling somewhere between 30 and 70 million. The adults of both genders are about the same size, growing to 9 feet in length with a weight of 500 pounds. It is quite common to see adults with prominent scars on their flanks or bellies caused by encounters with leopard seals, or perhaps killer whales. It has a pointed , rather dog-like snout and is often encountered resting on pack ice or ice floes.
LEOPARD SEAL
As its name suggests, this seal is a predator. It is the only Antarctic seal which regularly eats warm-blooded prey. A portion of its diet consists of penguins, but it also eats fish, krill, and even the young of other seals. The leopard seal has none of the cute appeal of the other seals, but despite it ferocious reputation there have been very few cases of unprovoked attacks upon humans. They are solitary animals and it is rare to see more than one individual in a given area. Leopard seals chase and catch penguins with great speed, often vigorously shaking their prey to break it into smaller pieces before swallowing it.
While our expedition was in Paradise Harbor, we had two curious leopard seals following our zodiac boats to and from shore, often coming a few feet from the side.
ROSS SEAL
The Ross seal is probably the least known of all the pinnipeds. It is a solitary animal and is quite rarely seen as it inhabits the thick pack ice along the fringes of the Antarctic continent. The Ross seal has very large and well developed flippers compared with other seals. The incisor and canine teeth are delicate, sharp, and re-curved for catching squid, its main source of food. It is very vocal, and one of its alternative names is 'singing seal.' Very little is known of its breeding habits. (Antarctic Primer pg 76-85)
