colored offspring, even when conditions are changed, it would seem that the 

 theory of natural selection in an isolated population remains the most logical 

 explanation for their color. A few of the mammals, such as the snowshoe 

 rabbit or varying hare and some of the weasels, adopt white for winter wear 

 among the snows and brown for the rest of the year. Some of the woodland 

 mammals have white markings which were formerly regarded as warning but 

 which now are generally considered protective. The white tail of running 

 rabbit or deer looks most conspicuous to man from his elevated viewpoint, 

 but to the crouching weasel or wolf the white patch blends with the sky and 

 makes the animal a much more difficult target. The broad white stripes of 

 the skunk may also be concealing coloration as far as the hunted mice or 

 hunting owls are concerned. The naturalist who has attempted to trail a 

 skunk during its early spring wanderings in search of a mate can testify that 

 at dusk among patches of unmelted snow the skunk has most concealing 

 coloration. Occasionally a wild mammal lacks the hereditary factors for 

 color and is an albino, white with pink eyes. Such an animal, hampered by 

 the usually associated physical handicaps, generally soon falls a victim to its 

 enemies. Occasionally only part of the factors for color are lacking or 

 changed so that the animal may be black or reddish. The common red fox 

 occasionally produces a few black or silver offspring in this way. The black 

 and silver foxes of our fur farms are usually different species from Alaska 

 or northeastern Canada. 



Some mammals have solved the problem of winter food scarcity by 

 hibernation or an approach to that condition. In this peculiar and little 

 understood condition the mammal loses control of body temperature and as' 

 sumes a temperature near that of the surroundings. Its respiration and circula- 

 tion become very slow, its eyes sunken, its lips lax, and it has all the 

 appearances of being dead, except for an occasional quiver. Its food require' 

 ments are reduced to a minimum, its body fat serving to maintain it. Strictly 

 speaking, only a warm-blooded animal can hibernate, and very few of them 

 do so completely. The term hibernation is commonly used, however, to 

 refer to the state of torpor in which many animals, including many of the 

 cold-blooded ones, pass the winter. Marmots, the jumping mice, and the true 

 ground squirrels are apparently the most profound hibernators, while some 

 of their close relatives show no indication of such ability. Bears, badgers and 

 raccoons usually pass the winter in a state of partial hibernation, although 

 in the southern parts of their ranges this may be much shortened or omitted. 

 Many other mammals store up food or fat and remain denned up for the 

 coldest part of the winter. Among the regular hibernators there is much 

 variation, the male often retiring for a shorter season than the female. An 

 occasional individual may remain active all winter. Some of the ground 

 squirrels have developed the power of entering this condition of suspended 



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