Although there are 35 species of seals, only six types live in Antarctica: Antarctic Fur Seals, Crabeater Seals, Leopard Seals, Ross Seals, and Weddell Seals. However, these six species make up the majority of the world's seal population. With no natural land predators, such as polar bears or man, Antarctic seals behave much differently than northern seals--showing little fear of man.
Seals are categorized into three families: true seals, eared seals (common to most zoos), and walruses (found in the arctic). All of the seals in Antarctica are true seals (no ears). Even without ears, seal hearing out of the water is as good as human's. In the water, their hearing is even better. Its theorized that seals use a type of sonar to locate food, much like what dolphins and whales use.
In addition to using sonar for navigation and locating groups of food, its believed seals use their whiskers as a form of radar. The whiskers detect movement in the water and allow the seal to zoom in a particular object. Through the use of their sonar and radar, seals can actually find food in complete darkness better than in the light.
As for their eyes, seals don't really see color but they are particularly sensitive to common sea water colors (greens, green-blues). Seals eyes have a silvery lining behind the retina, just like cats and other nocturnal/low-light hunters. This lining reflects the light back through the eye and increases the total amount of light absorbed by the eye--another necessary feature when hunting in the dimly lit depths of the oceans.
When in the water, a seal's nose closes automatically and doesn't reopen until it surface. Typically, a seal can remain underwater for 15 minutes (young) to 30 minutes (adults). This also is true of when they're sleep. Seals sleep just under the surface of the ocean and can resurface for air without waking.
Antarctic Fur Seals
Unlike other seals found in Antarctica, Fur Seals are not true seals. They are from the eared seal family. They reside on the rocky shores of islands found in western Antarctica and average adults weigh 350 pounds (160 kilos).
Although extremely sociable among other Fur Seals, they are known to bit humans without provocation and move well enough to outrun humans on land. These poor manners were not helped by the fact that Fur Seals were heavily hunted during the 19th century. At one point, their total population was reduced to a few thousand.
Fur Seals were placed under protection at the beginning of this century and have made a remarkable recovery. Their breeding season begins in December and takes place in very large, dense colonies. At colonies on South Georgia Island, seal populations increase by an average of 17% a year. This translates to their population doubling every five years.
Despite their name, Crabeaters eats mainly krill; crabs form only a small portion of the seals' diet. Crabeaters live at the edge of pack ice and are normally solitary animals. However during the breeding season, they will form small family groups consisting of the mother, father and a pup.
The Crabeater seal accounts for over half of the world's seal population. Estimates place the Crabeater's population in excess of 30 million. Its population explosion is possibly due to the decline of whales, the Crabeater's chief competition for krill.
The Crabeater's main predator is the killer whale (or orca). Occasionally whales will bump an ice floe which has seals on it in order to knock seal into the water. Leopard Seals also prey on the Crabeater, although typically only on the young.
Leopard Seals are the largest of the true Antarctic seals. (Southern Elephant Seals are more common on islands near and above the Antarctic Convergence, although they do venture south to the actual continent.) Leopard Seals can grow to over 11 feet long (3.4 meters) and weigh, on average, 1,200 pounds (540 kilos). They are rather easy to identify due to the reptilian-like head, long sinewy neck, and arched thorax.
Although commonly found on pack ice, leopard seals spend a good deal of their time patrolling the shores of penguin rookeries. Warm-blooded animals account for nearly 40% of the leopard seals' diet. Typically, they feed on penguins and small Crabeater seals. The remainder of their diet consists of krill (approximately 40%), fish, squid, and other invertebrates.
Because of its tendency to live on heavy pack ice where ships cannot pass, little is known about this species. What is known is they're nearly as large as Leopard Seals. Females Ross Seals can reach 11 feet in length (3.3 meters) and weight an average of 420 pounds (190 kilos). As with most Antarctic seals, males tend to be smaller.
Ross Seals are identified by the short heads and rather large eyes. Also, there often are strips starting at the chin and running along the sides of the neck to the chest. Their diet consists mainly of fish and squid, although they're not opposed to eating other invertebrates.
Due to the lack of knowledge about them as well as their infrequent sightings, Ross Seals are protected under the Antarctic Treaty.
Southern Elephant Seals
These are the big daddies of the Antarctic beach. Elephant Seals can tip the scale at a hefty 7,900 pound (3,600 kilos) and measure up to 15 feet (4.5 meters). They commonly are found throughout the sub-Antarctic islands, although some colonies are located near the continent.
Being larger in this specie, males dominate the breeding process. They, first, battle with other males to establish territory on the beach. To the victor goes the spoils; this includes harems which can include up to 50 females. Breeding colonies are terribly cramped for space. These multi-ton beasts lie next to and on top of each other. Often, pups are crushed under the weight of adult seals.
In order to satisfy their huge appetites, Elephant Seals dive deep into the ocean and feed on various forms of fish and squid.
One of the more commonly sighted seals, Weddells often are found in groups. Some of these groups contain several hundred seals, although this typically occurs during their breeding season (September to November). During this time, males engage in numerous territorial battles.
Unlike other species, these seals prefer to lie on snow and ice even when open land or rock is available. This trait, along with their desire to avoid Orcas, is one of the primary reasons Weddells are found on inland fast ice around the continent.
During the winter months, Weddells must maintain diving/breathing holes in the ice in order to feed. Feeding primarily on fish, Weddells can dive in excess of 1,000 feet (300 meters) in search of food. To make these long dives possible, they carry five time the amount of oxygen in their blood as human do. To get the most from this, Weddells slow their heart rate and limit blood circulation to vital organs such as the brain, kidneys, and liver.
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