MAMMALIA 361 



The weasel is the smallest animiil of the group. The body is very long 

 and "no tHTcker than a man's thumb." Its fur changes from brown in 

 summer to white in winter. This winter fur is known as ermine, and comes 

 from Alaska, Canada, Lapland, Russia, and Siberia. It is used not only 

 for ladies' garments, but for the robes and crowns of kings. The smallest 

 of all Carnivores is Putorius rixosus, of northwestern Canada. It is only 

 6 inches in total length and brown to the tip of its tail. In all other specira 

 the end of the tail is black. The change of color to white helps to retain the 

 body heat, and helps also to conceal the animal from its enemies and its 

 prey. Poulton believes that the cause of this change of color is the lower 

 temperature acting upon the skin, and that existing dark hairs become white 

 at the tips. Others maintain that in cold regions the summer pelage is re- 

 placed in winter by hairs which come in wholly white, while in warm regions 

 the new winter coat is brown. However, Doctor Coues says he has seen 

 many autumnal skins which were white at the roots and dark at the tips. 

 In any case, natural selection has preserved those individuals having the 

 power of changing the color of the fur until this character is now general. 



The dog family {Canidas) is universally distributed, with the exception 

 of New Zealand. These animals have a simple, cylindric cecum and usually 

 five toes. Perhaps the most striking feature of the family is the bladder- 

 like inflation of the auditory bulla, that part of the skull containing the 

 internal ear. This apparatus and sense is perfected in the dogs. Many of 

 this family are familiar. 



There are several genera, but the principal one is Canis, including our 

 dogs, wolves, foxes, and jackals. Huxley divides them into fox-like and 

 wolf-like dogs. The foxes are more active than the wolves, with a "broad 

 skull, sharper muzzle, larger ears, a more bushy tail, and, usually, longer 

 fur." They are notably clever and quick witted, and often show skill in 

 meeting new situations made by the advent of man. 



The typical fox is the common red fox {Vulpes fulvus), of wide distri- 

 bution. Our American form varies from the typical yellowish red, darkest 

 on the back and shoulders, to a very bright or very pale yellowish red. 

 It may have the markings on the spine and withers very dark and distinct, 

 making it a "cross-fox," or be totally black with a white-tipped tail, or black 

 with the tips of most of the hairs white, giving the fur a frosted or silver 

 appearance. Either of the last two cases is called "silver fox." These rare 

 and valuable variations may occur in the same litter with the normally 

 reddish ones. Foxes feed upon ground birds and their eggs, rodents, frogs, 

 lizards, insects, and fruits. They may be caught by rapid chase, by digging 

 the burrowing forms out of the ground — for the fox is naturally a burrower — 

 by stealthily creeping up on them, or by lying apparently dead until the vic- 

 tim approaches, and then pouncing upon it. While it does sometimes raid the 

 hen coops, the fox does good service in destroying rats, mice, and gophers. 

 It sometimes stores its surplus food. Its enemies are all the large cats and 

 wolves, as well as man and dogs in the so-called sport of fox chasing. The 

 red fox has a litter of seven or eight young; the southern gray fox, of four or 

 five. The gray fox is smaller. It climbs trees to get the "sour grapes" and 

 persimmons, but it cannot adapt itself to the prairies. The arctic fox 

 (Vulpes lagopus) furnishes another example of color variation under the 

 influence of a different climate. In the extreme north it is snow white all 

 the year round. A little farther south it is brown, with the under parts 

 lighter in summer and white in winter, while in the southern part of its 

 range, as in the Aleutian Island and parts of Greenland, it is most often bluish 



