Weddell Seal

Weddell Seal, large, bulky seal with a small head. Abundant throughout their range, these seals live primarily in the Weddell Sea at the southernmost reaches of the Atlantic Ocean. They occasionally venture north to the coasts of New Zealand, Australia, and even Uruguay. Weddell seals are equipped with body fat that enables them to maintain internal body temperatures similar to human body temperatures while swimming through freezing waters. Living on ice close to shore, Weddell seals are curious, but not fearful, toward humans.

These sizeable seals can weigh as much as 400 to 600 kg (880 to 1320 lb) and grow as long as 3.3 m (10.8 ft), with males slightly smaller than females. They have catlike faces and bluish-gray coats with lighter underbellies that fade to a rusty, grayish-brown during the summer. Silver or white streaks and splashes highlight the coats, especially on the undersides.

As top predators in the Antarctic marine ecosystem, Weddell seals are champion divers. They hold the record among seals for dives as deep as 600 m (1900 ft) and as long as 70 minutes. They have been studied extensively by scientists researching the physiology of diving. When swimming, they can reach speeds of 29 km/h (18 mph). These energetic hunters catch a plentiful variety of fish, and they have been seen sharing their catches of squid and octopus with their close relatives, Ross seals. Crab and other crustaceans round out their diet.

These nonmigratory seals spend much of their time on the ice. But during the winter, they take to the iced-over water, which is warmer than the frigid air. To survive, Weddell seals use their powerful incisors and canine teeth to maintain breathing holes, sawing and biting at the edges of the ice. This intensive work takes its toll: their strong teeth get worn down, and dental complications, including infection, cause numerous deaths. The seals also make resourceful use of undersea ice holes to escape predators, hiding out in crevices where larger adversaries cannot reach them.

As mating season approaches, the males, who are polygynous (mating with multiple females), stake out underwater mating areas up to 20 m (66 ft) in diameter by defending their territories with loud roars and barks. Following mating, gestation takes approximately 11 months. Shortly before the pups are born, which occurs between mid-October and mid-November, the pregnant females emerge from the water onto the ice to choose birthing areas near cracks that provide emergency exit holes back into the water. Each female gives birth to one pup, which typically weighs 25 kg (55 lb) at birth. Pups increase their weight four- or five-fold by the time they are weaned—approximately 50 days after birth. As weaning time approaches, mothers and pups are often seen going in the water together. Females mate again toward the end of the nursing period.

The Weddell seal must stay alert to natural predators, including the killer whale. Some of these seals have been killed for scientific research or to feed sled dogs at research stations, but they are not extensively hunted. An estimated 250,000 of these seals currently live in the Antarctic.

Scientific classification: The Weddell seal belongs to the family Phocidae of the suborder Pinnipedia, order Carnivora. It is classified as Leptonychotes weddelli.