The Weddell seal (Leptonychotes weddellii) is a relatively large and abundant true seal (family: Phocidae) with a circumpolar distribution surrounding Antarctica. The Weddell seal was discovered and named in the 1820s during expeditions led by British sealing captain James Weddell to the area of the Southern Ocean now known as the Weddell Sea. The life history of this species is well documented since it occupies fast ice environments close to the Antarctic continent and often adjacent to Antarctic bases. Weddell seals measure about 2.5–3.5 m (8 ft 2 in–11 ft 6 in) long and weigh 400–600 kg (880–1,320 lb). They are amongst the largest seals, with a rather bulky body and short fore flippers relative to their body length. Males weigh less than females, usually about 500 kg (1,100 lb) or less. Male and female Weddell seals are generally about the same length, though females can be slightly larger. However, the male seal tends to have a thicker neck and a broader head and muzzle than the female. A molecular genetic based technique has been established to confirm the sex of individuals in the laboratory. The Weddell seal face has been compared to that of a cat due to a short mouth line and similarities in the structure of the nose and whiskers. The Weddell seal grows a thin fur coat around its whole body except for small areas around the flippers. The color and pattern of the coat varies, often fading to a duller color as the seal ages. This coat molts around the beginning of summer. Adults show a counter-shaded coloration that varies from bluish-black to dark gray dorsally and to light gray/silver ventrally. Coats may change to shades of brown before the annual molt. Adult males usually bear scars, most of them around the genital region. Weddell seal pups are born with a lanugo of similar coloration and they molt after 3–4 weeks; later, they turn a darker color similar to that of adults. The pups are around half the length of their mother at birth, and weigh 25–30 kg (55–66 lb). They gain around 2 kg (4.4 lb) a day, and by 6–7 weeks old they can weigh around 100 kg (220 lb).