The leopard seal, Hydrurga leptonyx, is a species of earless seal or true seal and the second largest type, after the southern elephant seal. It is the only species within the genus Hydrurga. This seal is related to other true seals in the Phocidae family and is a Pinniped, a clade which includes sea lions, fur seals and walruses.
The leopard seal is an earless seal which is second in size only to the southern elephant seal. Their spotted bodies are large and muscular and can weigh from 200 kg up to 600 kg. The length of these seals can range from 2.4 to 3.5 meters, making them almost as long as walruses, but with half the normal weight. Contrary to many other seal species, the leopard female is slightly larger than males. The dentition of this seal is characteristic to carnivores, with sharp canines which can be 2.5 centimeters long. However, they also have molars that can lock together, an adaptation allowing them to eat krill.
This seal species inhabits the cold waters which surround the Antarctic continent. There are more populations in the western part of the Antarctic than in the rest of the continent. While many seals are constrained to the pack ice for most of the year, younger specimens may be able to swim further to the north to sub-Antarctic islands where they can spend the winter.
These seals are predators, and they can feed on birds, mammals as well as crustaceans and fish. Younger and smaller seals will mostly feed on krill in a similar way to the crabeater seal, while older and larger individuals may start hunting for prey. These seals hunt most species of penguins, and may even feed on other seal species such as the crabeater seals. The main prey of the sub-Antarctic island of South Georgia is the Antarctic fur seal. This seal is the second largest predator in the Antarctic region after the killer whale.
Males vocalize underwater for hours during the breeding season. This is done presumably to attract females. The males can emit loud sounds of up to 177 decibels. Younger males have more diverse songs and sounds while older males produce fewer and more standardized callings. Females usually have just one pup they give birth to on floating packs of ice during the austral summer. Leopard seal females ferociously protect their pups until they are able to protect themselves.