Physical Description
Adult seals (over five years old) grow to an average length of 230 cm (7.6 ft) and an average weight of around 200 kg (440 lbs). Females are on average 6 cm (2.5 in) longer and around 8 kg heavier than males, though their weights fluctuate substantially according to season; females can lose up to 50% of their body weight during lactation, and males lose a significant proportion of weight as they attend to their mating partners and fight off rivals. Large crabeater seals can weigh up to 300 kg (660 lb). Pups are about 120 cm in length and 20 and 30 kg at birth. While nursing, pups grow at a rate of about 4.2 kg a day, and can weigh as much as 100 kg by the time they are weaned after only two to three weeks.
Pups are born with a light brown, downy pelage (lanugo), until the first molt at weaning. Younger animals are marked by net-like, chocolate brown markings and flecks on the shoulders, sides and flanks, shading into the predominantly dark hind and fore flippers and head, often due to scarring from leopard seals. After molting, their fur is a darker brown fading to blonde on their bellies. The fur lightens throughout the year, becoming completely blonde in summer. Older animals become progressively paler, even when freshly molted, and may appear almost white.
Crabeaters have relatively slender bodies and long skulls and snouts compared to other phocids. Perhaps their most distinctive adaptation is the unique dentition that enables this species to sieve Antarctic krill. The postcanine teeth are finely divided with multiple cusps. Together with the tight fit of the upper and lower jaw, a bony protuberance near the back of the mouth completes a near-perfect sieve within which krill are trapped.
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