Pack-ice seal species
Several species of marine mammal (whales, dolphins and seals) live in the Southern Ocean. Four species of seal live in the pack-ice surrounding Antarctica. Together they are thought to comprise up to 50% or more of the world's total biomass of seals. These four species are totally or largely confined to the pack-ice, being dependent on the ice as a platform on which to breed and moult.
The crabeater seal was once described as the most abundant large, wild mammal on earth. Past estimates of crabeater seal abundance vary widely, between 8 to 50 million, although new data suggests that the population is not as large as previously thought.
Contrary to its name, the crabeater seal feeds almost entirely on krill. Because of its large body, widespread distribution and abundance, it is considered a key species in the krill-based food web of the Southern Ocean.
The leopard seal is the largest of the pack-ice seal species, weighing up to 600 kg. It has a varied diet, feeding on krill, penguins and other species of seal. Most adult crabeater seals have large scars which are thought to be the result of predation by leopard seals.
Although the bulk of the leopard seal population occurs in the pack-ice region, some animals are found hauled out on the sub-Antarctic islands.
The Ross seal is the least understood species of pack-ice seal, being rarely seen and inhabiting the most inaccessible regions of the pack-ice.
It is thought to feed on fish and squid, but most aspects of its biology and ecology remain a mystery.
The Weddell seal inhabits the most southerly regions of the pack-ice, hauling out onto 'fast' ice near the Antarctic coast. With many populations close to scientific stations, it is the most intensively studied of the four species. Its diet consists mainly of fish.