Crabeater seals are by far the most numerous seal species on the planet, with population estimates ranging from 7 million to as many as 75 million individuals. That also makes them one of the most abundant of all the large mammals on Earth. Their success is due in large part to a marvelous adaptation: their teeth.
Crabeater seals have a sieve-like tooth structure that filters Antarctic krill. This wonder of dental evolution—arguably the most specialized of any carnivore—allows them to suck in krill-rich water, after which they close their jaws and force the water back out between their teeth, with the krill trapped inside. Krill make up as much as 95% of the crabeater seal’s diet, allowing these specialist predators to thrive in the Antarctic. And despite their name, crabeater seals do not eat crabs.
While capable of diving to depths of up 400 meters, crabeater seals normally feed 20 to 30 meters below the surface. They do the majority of their feeding at night. It can be a risky business, as killer whales like to hunt crabeater seals. Leopard seals also prey upon crabeater pups and sometimes younger adults. Because of this, it’s common to see crabeater seals with numerous scars.
Of all the Antarctic seal species, crabeater seals are the most sociable. Younger seals gather in groups on the pack ice, sometimes with as many as 1,000 individuals. When it’s time to hunt, groups of hundreds of seals will dive together. Older seals tend to be less gregarious, preferring to hunt alone or in small groups of just three or four individuals.
Female crabeater seals, which are about 2.5 meters long and weigh 400 kg (similar to males), haul themselves up onto the pack ice to give birth. They’ll then spend the following three to four weeks on the ice, until the pup has been weaned. The newborn pups are about 120 cm long and weigh around 25 kg.