reduce the flow of blood near its skin to conserve body heat. The warmth of the foot pads is regulated independently from the rest of the body and is maintained at just above tissue-freezing point where the pads come in contact with ice and snow. In warm climates, the fur is coarser and scarcer than in northern wolves. Female wolves tend to have smoother furred limbs than males and generally develop the smoothest overall coats as they age. Older wolves generally have more white hairs on the tip of the tail, along the nose, and on the forehead. Winter fur is retained longest by lactating females, although with some hair loss around their teats. Hair length on the middle of the back is , and the guard hairs on the shoulders generally do not exceed , but can reach . A wolf's coat colour is determined by its guard hairs. Wolves usually have some hairs that are white, brown, gray and black. The coat of the Eurasian wolf is a mixture of ochreous (yellow to orange) and rusty ochreous (orange/red/brown) colours with light gray. The muzzle is pale ochreous gray, and the area of the lips, cheeks, chin, and throat is white. The top of the head, forehead, under and between the eyes, and between the eyes and ears is gray with a reddish film. The neck is ochreous. Long, black tips on the hairs along the back form a broad stripe, with black hair tips on the shoulders, upper chest and rear of the body. The sides of the body, tail, and outer limbs are a pale dirty ochreous colour, while the inner sides of the limbs, belly, and groin are white. Apart from those wolves which are pure white or black, these tones vary little across geographical areas, although the patterns of these colours vary between individuals. In North America, the coat colours of wolves follow Gloger's rule, wolves in the Canadian arctic being white and those in southern Canada, the U.S., and Mexico being predominantly gray. In some areas of the Rocky Mountains of Alberta and British Columbia, the coat colour is predominantly black, some being blue-gray and some with silver and black. Differences in coat colour between sexes is absent in Eurasia; females tend to have redder tones in North America. Black-coloured wolves in North America acquired their colour from wolf-dog admixture after the first arrival