MAMMALS 

 CHAPTER 15 



In common speech the mammals are usually referred to as "animals", a 

 general term which should include all living creatures except plants. The 

 mammals have felt the strain of competition with man more keenly than have 

 most of the other animals, so that the larger ones have lost out in the struggle 

 and have either become extinct or have their ranges much restricted. Most 

 of the smaller mammals have adjusted their lives to man's presence and by 

 extreme wariness or nocturnal or crepuscular habits have managed to survive. 

 Wherever a bit of wild country remains, unfit for agriculture but suitable 

 for animal breeding grounds, the smaller mammals remain. A brier patch, 

 a swamp or a rocky hillside, even on the outskirts of a city, may be a haven 

 of refuge. Studies have shown that in the vicinity of Chicago thirty-nine 

 species of wild mammals still survive and that around Northampton, Massa- 

 chusetts, after almost three hundred years of settlement, thirty-five species 

 yet remain. It is to be hoped that more of our waste and otherwise worthless 

 lands may be set aside as true sanctuaries for all forms of wild animal life. 



The native mammals are divided into seven main groups. Taxonomically 

 speaking, the first and "lowest" in the list of our mammals is the opossum. 

 It is the only North American representative of the Marsitpiaha, mammals 

 that produce their young in a very early stage and let them finish their de- 

 velopment in an abdominal pouch or marsupium. The Xenarthra or American 

 edentates are represented in the United States by only one species, the nine- 

 banded armadillo, found along the Mexican border. It is characterized by un- 

 specialized teeth and a strange bony covering or shell. The Chiroptera or 

 bats are widely distributed. They were at one time placed at the head of 

 the class Mammaha, because they are the only vertebrates, other than birds, 

 that can truly fly. The ArUodactyla, ungulates or hoofed animals, include the 

 peccary, cattle, deer and pronghorn antelope. The cattle family, of which 

 the bison, bighorn sheep and mountain goat are representatives, have horns — 

 unbranched, permanent structures present in both sexes and consisting of 

 bony cores covered with thin material called horn. The deer have solid, 

 branched structures called antlers, which develop only in the male in all 

 native deer except the caribou and which are shed annually. The prong- 

 horn antelope stands alone in having singly branched horns the outer layers 

 of which are shed each year — apparently a halfway stage between antlers 

 and horns. The Rodentia or gnawing animals are the largest group of mam- 

 mals. Here belong rats, mice, squirrels, woodchucks, beaver, chipmunks and 



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