Weddell seal in the context of James Weddell

The leopard seal (Hydrurga leptonyx), also referred to as the sea leopard, is the second largest species of seal in the Antarctic (after the southern elephant seal). It is a top order predator, feeding on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins, its only natural predator being the orca. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal, and the Weddell seal, which are all Antarctic seals of the tribe Lobodontini.

A circumpolar distribution is any range of a taxon that occurs over a wide range of longitudes but only at high latitudes; such a range therefore extends all the way around either the North Pole or the South Pole. Taxa that are also found in isolated high-mountain environments further from the poles are said to have arctic–alpine distributions.

Animals with circumpolar distributions include the reindeer, polar bear, Arctic fox, snowy owl, snow bunting, king eider, gyrfalcon, brent goose and long-tailed skua in the north, and the Weddell seal and Adélie penguin in the south.

The true seal tribe Lobodontini, collectively known as the Antarctic seals or lobodontin seals, consist of four species of seals in four genera: the crabeater seal (Lobodon carcinophaga), the leopard seal (Hydrurga leptonyx), the Weddell seal (Leptonychotes weddelli), and the Ross seal (Ommatophoca rossii). All lobodontine seals have circumpolar distributions surrounding Antarctica. They include both the world's most abundant seal (the crabeater seal) and the only predominantly mammal-eating seal (the leopard seal). While the Weddell seal prefers the shore-fast ice, the other species live primarily on and around the off-shore pack ice. Thus, though they are collectively the most abundant group of seals in the world, the combination of remote range and inaccessible habitat make them among the least well-studied of the world's seals.