The crabeater seal has remarkable agility on snow and ice, and is one of the quickest seal species when it moves on land (3). It moves using a almost serpentine (snake-like) gait, thrusting its forelimbs alternately against the snow, moving its pelvis from side to side and keeping its hind limbs held together off the ground (3) (4). The crabeater seal’s method of travelling leaves long, distinctive tracks along the ground as its body is dragged through the snow, with characteristic alternating flipper imprints on either side (4).
Contrary to its name, the crabeater seal very rarely feeds on crabs. Instead, Antarctic krill (Euphausia superba) makes up around 95 percent of the crabeater seal’s prey, while the remainder of its diet is comprised of cephalopods, fish and crustaceans (1) (2) (4).
The crabeater seal has specialised, finely lobed teeth which are thought to be an adaptation to its almost exclusively krill-based diet. In fact the crabeater seal’s scientific name, Lobodon, is derived from Greek words meaning ‘lobed tooth’ (2). The teeth interlock to form a sieve through which the krill are filtered, and a ridge of bone fills the gap between the teeth and the back of the jaw, stopping prey from escaping from the mouth while feeding (1) (2) (3) (4). The crabeater seal feeds mostly at night (1) (3), making fairly deep dives in search of its prey (1). During the day the crabeater seal will rest, hauled out on ice floes (1) (2) (4).
Generally, the crabeater seal spends most of its time alone or in small groups. However, much larger groups of seals, sometimes numbering around 1,000 individuals, have been observed to haul out on ice floes. This is particularly common during the annual moult in January and February. Herds of up to 500 individuals have also been known to swim and dive together (1). During the spring, mature and juvenile crabeater seals will segregate, with juveniles forming large aggregations on the land while the mature adults remain on the pack ice for the breeding season (4).
The breeding season of the crabeater seal is fairly short (1). Mating takes place from October to December and occurs on the ice (3). The crabeater seal has a fairly long gestation period of around 11 months, which probably involves a period of delayed implantation (3) (4).
The female gives birth to a single pup between September and November the following year, with a peak in births around mid-October (1). The female is usually joined by a male just before the birth, who will protect the female and the newborn pup from other males and potential predators (2) (3) (4). The pup remains in close contact with the female until it is weaned, which usually occurs around three or four weeks after birth. During this time, the female will prevent the male from attempting to mate with her by using aggressive vocalisations, biting the male around the mouth and flippers, and chasing it away (1) (4). However, once the pup is weaned, the female will come back into oestrus and the male will forcefully drive the female and pup apart before mating with the female (3).
At birth, the crabeater seal pups are around 1.1 to 1.5 metres long and weigh between 20 and 40 kilograms (1) (3). They grow rapidly, weighing more than 100 kilograms by the time they are weaned (2). The young are nearly fully grown after two years, although sexual maturity is not attained until they are between three and six years old (3).