Leopard Seal

The one that looks like a dinosaur

Most seals look friendly whether they are or not. The leopard seal does not have that problem. It has a long, wide, flat skull, a mouth that opens improbably far, and a serpentine neck it can rear back and strike with. Photographers who work in Antarctica describe the first close encounter as unsettling in a way that no other seal is, because the animal looks less like a seal than like something that survived from an older world.

They are enormous. Females, which are the larger sex here, can pass eleven feet and weigh more than a quarter ton. The coat is dark silver-grey above and pale below, spotted all over, which is where the leopard name comes from. Along with orcas, they sit at the very top of the Antarctic food web. Nothing else routinely hunts an adult leopard seal.

The teeth do two completely different jobs

Here is the fact that makes leopard seals genuinely strange. They are famous as penguin hunters, and they do hunt penguins, patrolling the ice edge where the birds enter the water. But roughly 45 percent of their diet is Antarctic krill, animals the size of your fingernail.

Their teeth do both. The front canines are long and sharp, exactly what you would expect on a predator that takes seals and penguins. But the cheek teeth behind them are elaborately lobed, and when the jaw closes those lobes interlock into a sieve. The seal takes in a mouthful of krill-rich water, closes down, and forces the water out through the gaps, straining out the krill like a baleen whale in miniature.

So the same mouth that can kill a young crabeater seal also filter-feeds on plankton. Very few predators anywhere carry that much range in a single set of jaws.

How they actually hunt penguins

The hunt is not the wild chase people picture. A leopard seal will often wait, nearly motionless, beneath the lip of an ice floe where penguins launch themselves into the sea. It hangs in the water column and watches the surface, then accelerates upward.

Once a penguin is caught, the seal cannot chew it in the way a land carnivore would, having the wrong sort of jaws for slicing. What often follows instead is a violent thrashing at the surface, the seal beating the carcass against the water until it comes apart into pieces small enough to swallow. It is genuinely difficult to watch, and it is also efficient.

Crucially, penguins are seasonal. Leopard seals concentrate on them when colonies are active and accessible, and swing back toward krill, fish and squid the rest of the year. They are opportunists first and specialists second.

Solitary, and loud about it

Leopard seals live alone. Outside of breeding they generally do not tolerate each other's company, spread thinly across the pack ice around the entire Antarctic continent.

That makes finding a mate a real logistical problem, and the solution is sound. In the austral spring, males sing underwater for hours at a stretch, day after day, producing stylized trills and hoots that each individual repeats in his own consistent pattern. The calls carry a long way through cold water. Females broadcast too, in a different register, when they are ready to breed.

The whole courtship happens in the water and is almost never observed directly. Pups are born on ice floes, and the mother raises the pup entirely alone, digging a shallow hollow in the ice and staying with it for about a month before it must fend for itself.

How many are there, really

Nobody is certain, and the honest answer is interesting in itself. The IUCN lists leopard seals as Least Concern, based on an assessment estimating on the order of 18,000 mature individuals. Other published estimates range far higher, into the hundreds of thousands, and a 2022 study proposed a figure closer to 35,000 across Antarctica.

Why such wide disagreement? Because counting them is close to impossible. They are solitary, they live scattered across enormous stretches of drifting pack ice at the bottom of the world, and they spend much of their time underwater. Surveys catch a thin slice of a very large area and have to extrapolate.

What is not in dispute is the dependency. Leopard seals need krill, and they need ice to breed on. Both are tied directly to how the Southern Ocean responds to a warming climate, which makes this apex predator considerably more fragile than its reputation suggests.