At birth, grey seal pups weigh approximately 16 kg and have long, creamy white fur which is shed after the first three weeks of life. They fatten quickly on the rich milk from their mothers, and by moulting age have nearly quadrupled in body mass. At this time the young seals show coat patterns which differentiate the sexes. The female grey seal is silver-grey in colour, with small scattered dark spots, while the males are a dark grey with silver grey spots. The three populations of grey seals differ in exact colorings (grey, brown, silver), however the patterns are similar among the individual sexes -- female grey seals have dark spots on a lighter background while the males have a lighter spotting on a dark background fur, but both sexes in the three populations have a relatively dark back and lighter belly.
In addition to coat markings, the nose of a grey seal can distinguish a male from a female. The male grey seal has a long-arched roman nose which is the basis for its Latin name, Halichoerus grypus, meaning the hooked-nose sea pig. The shoulders of the male are massive with the overall bulk supplemented by a buildup of scar tissue from fighting during breeding seasons. The average adult male reaches his maximum size of 2.2 meters long and 220 kg at 11 years of age. The female is smaller and does not attain full size until approximately 15 years of age, reaching an average weight of 150 kg and length of 1.8 meters (measured from nose to tail). She has a more narrow, short nose and a straight profile to the dorsal surface of the head.
Range mass: 150 to 220 kg.
Range length: 1.8 to 2.2 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; sexes shaped differently