Leopard Seal
(Hydrurga leptonyx)


Distribution and Numbers
So named because of its spotted coat, and with a long slender body and large almost reptilian head, the leopard seal is widely distributed in high southern latitudes. It is usually found on the edges of the Antarctic pack ice, but individuals are also present year-round and seasonally on some subantarctic islands. Population size is difficult to determine, especially as the leopard seal inhabits such a large inhospitable area and is usually solitary, but an estimate of 220,000-440,000 has been made. Leopard seals are regular visitors to Australia and New Zealand, and wandering seals have also been found on the southern coasts of South America and South Africa. The most northerly sighting of the species is from the Cook Islands.
Hydrurga leptonyx - Image 1

Photo: Rodrigo Hucke-Gaete,

Universidad Austral de Chile
As with other seals of the Antarctic pack ice, leopard seals have been protected from commercial hunting due to their inaccessibility and the high cost of operating in the area. All killing of seals in the Antarctic region is regulated by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals (CCAS). In 1986-1987 however two Soviet commercial sealing ships killed 649 leopard seals. A plan by Norwegian scientists to kill 20 leopard seals, as well as 60 other seals, in the summer of 2000-2001 for research into environmental contaminants was cancelled after the Norwegian government rejected the plan. Several environmental organisations had vigorously opposed the plan, questioning its necessity and also its appropriateness given the option of alternative non-lethal sampling techniques.
As populations of other marine mammals that were previously hunted in the Southern Sea, especially cetaceans, recover to pre-exploitation levels, competition for food will increase. This is especially the case for krill which is an important element of the leopard seal diet. There is a fishery for krill, a crucial element in the food web, around Antarctica and some krill-fishing nations are seeking an increase in the quotas. In January 1998 the Environmental Protection Protocol to the Antarctic Treaty was ratified, implementing environmental measures such as the banning of mining and oil drilling in Antarctica for at least 50 years and the banning of refuse disposal and the use of pesticides in the region.
Hydrurga leptonyx - Image 2

Photo: Michael Bryden,
University of Sydney
The distribution of leopard seals is significantly influenced by the annual expansion and contraction of the pack ice surrounding the Antarctic continent. Higher densities of leopard seals are found on broken ice near the pack ice edge. The leopard seal often hauls out on islands near the continent when the ice contracts, and immature seals are known to gather on subantarctic islands as they migrate north during late autumn and winter when the ice expands. Very little is known about the breeding habits of the leopard seal, but it has been suggested that pupping normally takes place in November and December and that there is a short breeding season about a month later, mating probably taking place in the water.
It is thought that leopard seals most likely give birth on non-fast ice and that there is probably a very short period of suckling, lasting perhaps a month, in which the pup puts on weight and protective blubber very quickly. Leopard seals are known to be very vocal during the breeding season, their calls tending to be soft and lyrical. There are also some regional variations in their calls, which has led to suggestions that there are separate breeding populations with only limited interactions. Pups are born with a soft thick coat, being very similar to the adult coat which is grey coloured and spotted, darker on the back than on the front. Adults usually moult between January and February.
Leopard seals eat an amazingly large variety of food, using their wide gaping mouths and massive jaws to great effect. In winter their most important food is krill. They also eat cephalopods, fish and other seal species, especially newly-weaned crabeater seals during December and January. Penguins are an important part of the diet of some leopard seals in late January and February. Leopard seals are rather cumbersome on land and do their feeding in the water where their large fore-flippers, unusually long for a "true" seal, allow them great speed and manoeuvrability. Some leopard seals are preyed on by killer whales.
The leopard seal is the largest of the four Antarctic seal species. Adult males can measure up to 2.5-3.2m in length and weigh 200-455kg, while adult females are slightly larger at 2.4-3.4m in length and 225-591kg. Pups are born measuring 1.5-1.6m in length and weighing about 35kg. The pup mortality rate in the first year is about 25%. Females probably achieve sexual maturity at 3-7 years, males at 2-6 years. The longest dive recorded is about 15 minutes - due to its feeding habits the leopard seal probably does not need to dive deeply. Leopard seals can live for over 26 years.
Hydrurga leptonyx - Image 3

Photo: Michael Bryden,
University of Sydney