Seals of Antarctica

In Antarctica, seals are one of the most commonly seen and distinctive (because of their size) animals, sleeping on beaches or lazing on ice floes. But these mammals are not lazy, for we see them only when they are resting. Their feeding activity is mainly done under water, out of sight, and during the night.  Seals are air-breathing mammals with dense fur coats, who come ashore or on to ice to give birth to pups.

Of the six species of seals found in Antarctica, four of them –the Ross, the Crabeater, Leopard and Weddell - inhabit the ice and icy waters which surround this continent.

All are confined to Antarctica and seldom found on land. The other two species - the Antarctic fur seal and the Southern Elephant seal-usually can be found on the shoreline and rarely encountered on the ice

Crabeater seals are the most abundant in the world, with populations ranging between 10 and 50 million seals. They do not eat crabs, they eat krill. No other seal is so specialized in eating one type of food. Where most mammals have molars for chewing or cutting food, this breed has molars that are highly modified for filtering food from the water. When the mouth is closed the upper and lower teeth mesh to form a sieve to trap krill while water is expelled. They are probably the most common seals in the world, yet few people see them because they inhabit the pack-ice zone around Antarctica. They seldom come up on land. Leopard seals and killer whales prey on Crabeater seals, particularly the young in their first year.

 

Leopard seals have “leopard spots” on their elongated bodies, powerful fore flippers and a large head with a menacing gape. They are not gregarious and spend most of their time in the pack-ice zone.  They are well known for eating penguins, especially the newly fledged chicks, but krill makes up a far larger component of their diet. Their penguin-hunting behavior is most common late in summer when the chicks take their first foraging trip in the water. Leopard seals have attacked humans on several occasions. With an increasing number of recreational scuba divers visiting Antarctica, the number of aggressive encounters with these animals may increase.  

Southern Elephant Seals are the largest seals in the world, the males weighing in over four tons. One such seal can weigh more than two rhinoceroses. It is the most accomplished diver and has been recorded descending more than one mile.  They come ashore only to breed and to molt, and more than 80 per cent of their time is spent in the ocean.  They breed in the sub Antarctic islands and venture into Antarctica in summer.

Weddell seals are the most southerly occurring mammal in the world. It is the only species that inhabits the fast-ice zone fringing the Antarctic continent. In this zone, the sea freezes in solid sheets that fasten on to the land, forming an almost uniform roof over the water.   They have smart “cat-like faces”, upturned mouths and short whiskers.

The Antarctic Fur Seal have small external ear-flaps and use fore flippers to swim. It is the only seal that can sit upright on its front flippers, just like the performing sea lions in circuses. While all the other species move on land and ice like inchworms, Fur seals are capable of raising themselves off the ground. They are unique among the Antarctic seals in that they can rotate their hind flippers forward and support some of their body weight on these limbs. This makes them very agile and fast when moving on shore. They can run faster than most people, especially those people wearing a parka and rubber boots. I personally saw a photographer with tripod being pursued by one on land when he tried a photo shoot with what he thought was an usually big boulder. The population of this particular breed has recovered remarkably since near-extinction form commercial harvesting in the early 1800’s. As recently as 1933 it was estimated that there were only 60 living on Bird Island in South Georgia. Today, the population there exceeds 65,000.

The Ross seal is a species that resides in the areas of the Antarctic seas where the pack ice is the densest. They are the shortest of the Antarctic seals with very small heads and tiny teeth. Their eyes are very large, and are thought to be an adaptation for feeding on squid in the low light conditions found at great depth under the pack ice. Out of the water, they seem to be more vocal than other Antarctic seals. A variety of calls and trills have been reported which brands them in the group of “singing seals.”

A non-breeding seal does not have any need to leave the water, for a seal can comfortably rest at the surface and get all its food from the sea. Giving birth, known as pupping, requires a solid platform and Antarctic seals haul out onto ice or land for this process. All species can have one pup per year, and females mate again after giving birth.

 

On our trips to shore, our guides were insistent that we be very careful of approaching too close to the sleeping seals. They may look harmless, posed as large boulders, but they can be very aggressive if annoyed.