The Leopard seal (Hydrurga leptonyx) is the second largest species of seal in the Antarctic (after the Southern Elephant Seal), and is near the top of the Antarctic food chain. It is most common in the southern hemisphere along the coast of Antarctica and on most sub-Antarctic islands, but can also be found on the coasts of southern Australia, Tasmania, South Africa, New Zealand, Lord Howe Island, Tierra del Fuego, the Cook Islands, and the Atlantic coast of South America. It can live twenty-six years, possibly more. Orcas are the only natural predators of leopard seals.
The leopard seal is large and muscular, with a dark grey back and light grey on its stomach. Its throat is whitish with the black spots that give the seal its common name. Females are generally larger than the males. The bulls are generally to and weigh between and , while cows are between and in length and weigh between and .
Compared to most phocids, the Leopard seal is highly evolved for its role as keystone predator. Although it is a true seal and swims with its hind limbs, it has powerful and highly developed forelimbs similar to sea lions, giving it a similar maneuverability, a classic example of convergent evolution. Like these eared seals, the Leopard Seal is a shallow water hunter, and does not dive deep like the other seals of the Antarctic (the Weddell seal, the Ross seal and the two species of elephant seals) which can all dive to several hundred meters in search of squid. The leopard seal has an unusually loose jaw that can open more than 160 degrees allowing it to bite larger prey.
Like most carnivores, its front teeth are sharp, but its molars lock together in a way that allows them to sieve krill from the water, similar to the Crabeater seal. Its senses of eyesight and smell are highly developed. These senses, coupled with a streamlined body that enable the seal to move swiftly through the water, ensures that it is a formidable predator.
The Leopard Seal is a solitary creature and comes together in small groups only when it is time to mate. The female digs a hole in the ice and, after a nine month gestation, the female gives birth to a single pup during the Antarctic summer. She protects the pup until it is able to fend for itself.
The leopard seal is bold, powerful and curious. In the water, there is a fine line between curiosity and predatory behavior, and it may 'play' with penguins that it does not intend to eat.
The leopard seal has canine teeth that are . It feeds on a wide variety of creatures: smaller seals probably eat mostly krill, but also squid and fish. Larger leopard seals probably switch to feed on King and Emperor Penguins, and, less frequently, other seals such as the Crabeater Seal.
When hunting penguins, the leopard seal patrols the waters near the edges of the ice, almost completely submerged, waiting for the birds to enter the ocean. It kills the swimming bird by grabbing the feet, then shaking the penguin vigorously and beating its body against the surface of the water repeatedly until the penguin is dead. Previous reports stating that the leopard seal skins its prey prior to feeding have been found to be incorrect. Lacking the teeth necessary to slice its prey into manageable pieces, it flails its prey from side to side in order to tear and rip it into smaller pieces.