Leopard Seal

The leopard seal is the predator that patrols the underside of Antarctica’s ice. Long, muscular, and heavy-headed, it sits near the top of the Southern Ocean food web — above every other seal, above the penguins — with only the killer whale ranked higher.

Overview

Leopard seals live around the pack ice that fringes Antarctica, hauling out on floes to rest and spending the rest of their time hunting in the surrounding water. They are solitary — a leopard seal shares its patch of ice with no one and defends a hunting territory around penguin colonies and seal breeding sites. Individuals wander widely, and in some years dozens turn up on the beaches of southern Australia, New Zealand, and South America.

Physical characteristics

The leopard seal is built differently from the plump, dog-faced seals people usually picture. It is long and slender, with a disproportionately large, flat-topped, almost reptilian head, a wide gape, and a powerful, sinuous body. Females are larger than males, reaching nearly four metres and 500 kg or more.

The mouth carries two kinds of teeth: long, sharp canines at the front for seizing large, struggling prey, and three-lobed cheek teeth that interlock to form a sieve.

A predator that also filters

That sieve is the key to the leopard seal’s flexible diet. It is famous as a hunter of penguins — which it catches at the water’s edge and skins by flailing against the surface — and of young crabeater and Weddell seals, which carry the scars of leopard seal attacks. But it also takes fish and squid, and it filter-feeds on krill, straining swarms of the shrimp-like crustaceans through its lobed teeth. In some individuals, krill is nearly half the diet.

Behaviour

Leopard seals are among the most vocal seals. In the breeding season, males hang vertically in the water below the ice for hours, producing loud, stylised, almost musical calls — trills, moans, and pulsed notes — that carry for kilometres and are thought to advertise for mates. Because they live alone on remote ice, the sound is one of the few ways a leopard seal broadcasts its presence.

Reproduction and life cycle

Mating happens in the water in the Antarctic summer. After a pregnancy of around 11 months, a female hauls out onto an ice floe and gives birth to a single pup, which she nurses for about a month before it takes to the water. She raises it alone; the male plays no part.

Threats and conservation

The leopard seal is listed as Least Concern, with a population thought to be in the tens of thousands, though it is genuinely hard to count because the animals are dispersed across some of the most inaccessible ice on the planet. It has no significant direct threats from people. The long-term risks are indirect — changes to Antarctic sea ice and to the abundance of krill, driven by climate change and by industrial krill fishing, which could ripple up the food web to the top predator that depends on all of it.