Leopard seal  (Hydrurga leptonyx)

Classified as Least Concern (LC) on the IUCN Red List (1).

Like its terrestrial namesake, the leopard seal is a formidable hunter with a sinuous body and powerful jaws that open widely to reveal exceptionally long canine teeth (3) (4) (5). The head is large and reptile-like, while the neck is long and flexible, allowing it to pull the head backwards before striking prey like a snake (3) (4). Unusually for a true seal (4), it swims with graceful simultaneous strokes of large, elongated fore-flippers, providing both speed and manoeuvrability (5) (6) (7). In addition to the menacing canines, which are adapted for seizing larger animals such as penguins and seals, it also has a set of unusual interlocking molars that are used as a sieve for krill (2) (3). Adults have a silvery-grey to black coat, with variable dark spots and a paler underside (4) (7). Juveniles, however, have a much softer, thicker coat with a dorsal stripe, and a light gray underside, peppered with dark spots (7). Although the sexes are similar in overall appearance, unusually for a seal, the female is slightly larger than the male (1) (2) (3) (8).

The leopard seal has a circumpolar distribution, occurring on the coast of the Antarctic continent, north throughout the pack ice where the highest densities are found, as well as around many of the sub-Antarctic islands. Vagrants have also been seen as far north as the coasts of South Africa, South America, Australia and New Zealand (1) (2) (3) (5).

The main habitat of the leopard seal is the Antarctic pack ice, and its associated ice bergs and smaller ice floes (3).

The leopard seal is famed for its prowess as a hunter, taking more warm-blooded prey than any other pinniped (2) (6). Being cumbersome on land, it typically only hunts in the water, with penguins and even other seals habitually falling prey to its stealthy attacks (2) (3) (6). However, somewhat contrary to its fearsome reputation, krill actually takes up the largest proportion of the leopard seal’s diet (up to 50 percent), particularly during the winter months when other food sources are scarce (2) (3). Indeed, predation on penguins in the vicinity of the rookeries is seasonal and appears to be the preserve of a relatively small number of seals, with most preferring to forage further out to sea (6) (8). In addition to krill, penguins and seals, a range of other food items feature prominently in its diet, including fish, squid, other seabirds, and occasionally the carcasses of whales (1) (3) (4) (6).

The leopard seal is a solitary species, both at sea and on the ice, with groups only ever being formed by temporary mating pairs and by mother and pup pairs (1) (3). Mating occurs during the height of the Austral summer, with birthing taking place between early October and January (1) (2). Each mother gives birth to single pup, which is weaned on the ice floes of the pack-ice for around a month (2) (3) (7). Sexual maturity is reached when the seals are around four to five years old, slightly later in males, and longevity in the wild is estimated to be over 26 years (1) (6).

Little is known about the seasonal movements of the leopard seal, but periodic northwards movements do occur, probably in response to changes in the availability of food and the location of the pack ice. Typically, the mature adults remain around the pack ice year round, while the younger juveniles venture into the sub-Antarctic between June and October (3).

The inaccessibility of the leopard seal’s Antarctic habitat has protected this widespread and abundant species from being targeted commercially, both in the past and today (1) (7). While there are currently no major threats, several factors are of some concern for the long-term future of this species, including increasing disturbance from seasonal tourism, the potential spread of disease, the commercial harvest of krill, and probably most importantly, the unknown impacts of climate change. A reduction in the area of pack-ice associated with global warming would not only affect the amount of habitat available for pupping and resting, but it is likely to also affect the availability of prey species (1).

Owing to its widespread occurrence and large population size (estimated at 220,000 -400,000 individuals in 1984), the leopard seal is currently classified as Least Concern on the IUCN Red List. Furthermore, in common with all Antarctic seals, the leopard seal is protected by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals, which ensures that any future commercial harvests would be regulated (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the Antarctic Treaty and Convention for the Conservation of Antarctic Seals, see:

• British Antarctic Survey:
  http://www.antarctica.ac.uk/about_antarctica/geopolitical/treaty/index.php

To find out more information on the leopard seal, visit:

• BBC Wildlife Finder:
  http://www.bbc.co.uk/nature/species/Leopard_Seal