486 



COLLEGE ZOOLOGY 



teeth; the fourth premolar of the upper jaw 

 and the first molar of the lower jaw bite on 

 one another like a pair of scissors and are 

 called shearing teeth. 



Wolves and foxes walk on their toes 

 (digitigrade, Fig. 348). The red fox is the 

 most common of all the foxes in America. 

 The arctic or blue fox may become perfectly 

 white in winter, enabling it to creep up on 

 its prey unseen. Wolves may hunt in packs 

 and must be controlled where they destroy 

 great numbers of deer, calves, and sheep; 

 they are shot and trapped whenever possible. 



The cat family includes the cat, puma 

 (also called mountain lion, cougar, or pan- 

 ther) (Fig. 366), leopard, lion, tiger, lynx, 

 and cheetah. 



Bears are all plantigrade (Fig. 348); they 

 are large awkward-appearing animals with 

 rudimentary tails. 



The mustelids constitute a large family 

 of small fur-bearing animals. About 50 spe- 

 cies inhabit North America. The otter is 

 adapted for swimming by webbed feet and 

 a powerful tail. The mink is also fond of 

 water. The weasel is one of the smallest of 

 the mustelids and very bloodthirsty. The 

 skunk (Fig. 356B) is notorious because of 

 the powerful odor of a secretion which it 

 can eject from a pair of scent glands which 

 open into the anal canal. 



The aquatic carnivores are greatly modi- 

 fied for life in the water. Both fore- and 

 hindfeet are fully webbed and serve as 

 swimming organs. The body has acquired a 

 fishlike form suitable for progress through 

 the water. They are chiefly marine, but a 

 few inhabit fresh water or swim up rivers. 

 The fur seal (Fig. 352F) breeds on the 

 Pribilof Islands in Bering Sea, but at other 

 times occurs along the coast of California. 

 The California sea lion is often seen in cap- 

 tivity. Adult male walruses (Fig. 352E) may 

 weigh over a ton; the canine teeth of the 

 upper jaw are very long, and are used to dig 

 up mollusks and crustaceans from the 

 muddy bottoms and to climb up on the 



blocks of ice in the Arctic seas where they 

 live. 



Whales 



The whale is the largest living animal; it 

 is adapted to life in the water. It possesses 

 a very large head with elongated face and 

 jaw bones; the forelimbs are modified as 

 paddles (flippers), and there is no external 

 trace of hindlimbs; the tafl is flattened 

 horizontally and forms two lobes, the 

 "flukes"; the eyes are small; and there is no 

 external ear. In the sperm whale the nostrils 

 form a single opening; and the warm moist 

 air which is forced from it condenses in 

 the cold atmosphere, appearing like a spout 

 of water. Only a few hairs are present about 

 the mouth. Beneath the skin is a thick layer 

 of fat or blubber, which takes the place of 

 the insulating hair of most mammals. The 

 teeth on the lower jaw of the sperm whales 

 are numerous and conical in shape; in whale- 

 bone whales there are no teeth, but there 

 are numerous parallel horny plates of whale- 

 bone on the sides of the upper jaw. 



The sperm whale (Fig. 352D) reaches a 

 length of 75 feet and is the largest toothed 

 whale. Moby Dick was a sperm whale, and, 

 according to the novel and the movie by 

 that name, one of enormous size. In the 

 large head is a cavity filled with as much as 

 a ton of fine oil (sperm oil). Other species 

 of toothed whales are the common dolphin, 

 the narwhal, the killer whale (Fig. 337), 

 and the common porpoise. 



The sulfur-bottom, a whalebone whale, 

 inhabits the Pacific from California to Cen- 

 tral America. The blue whale (Fig. 359) is 

 the longest of all whales and the largest 

 animal in the history of the world. It reaches 

 a length of 105 feet and a weight of about 

 125 tons. It summers near polar ice packs 

 of both poles, but winters in temperate 

 waters. Other species of whalebone whales 

 are the gray whale, the humpback whale, 

 and the common rorqual. Some whales may 



