MAMMALS OF YOSEMITE NATIONAL PARK 



55 



3 inches 



Aplodonlio 



y/*\NH*277 



±023 

 3 



$i*22 



The flesh-eaters (Carniiora) , typified 

 by bears, dogs, cats, weasels and the like, 

 have prominent canine teeth which, to- 

 gether with the strong incisors or front 

 teeth, equip them for seizing and holding 

 living prey. Powerful jaw muscles assist 

 in biting and tearing. Most members of 

 the order have sharp jaw teeth with blade- 

 like crowns, well-suited for a scissors- 

 like action in cutting and chewing flesh, 

 tendons and bones. The bear is a notable 

 exception to this condition, having 

 broad, flat crowns on the jaw teeth 

 which are more useful to such animals 

 that eat almost anything, from ants to 

 carrion. 



Rodents, or gnawing mammals, are 

 characterized by four chisel-like front 

 teeth, two long uppers which overlap the 

 two prominent lowers. These incisors are 

 kept sharp by differential wear in the 

 gnawing process. The front surface of 

 the tooth is hard, wear-resisting enamel 

 which xemains as a sharp edge after the 

 softer dentine has eroded back. The wear- 

 ing down is compensated by continual re- 

 newal, the teeth pushing out from the 



/ /nch 



roots deep within the jaws. The canines 

 are lacking but there are competent jaw 

 teeth for the grinding up of food cut 

 by the incisors. 



The rodent skull figured is from the 

 mountain "beaver" or Aplodontia (see p. 

 64). If one is accustomed to thinking 

 of rodents as being only small creatures, 

 such as rats and mice, it should be re- 

 membered that the golden beaver (Cas- 

 tor canadensis, subauratus) attains a 

 weight in the neighborhood of 40 pounds, 

 yet is very definitely a rodent! 



A\ule Deer 



$Hi>3z 



Cony 



y*NH *I33 



o Z 3 



^36 



Rabbits, hares and conies (Lagomor- 

 pha) outwardly resemble the rodents in 

 many respects. The front teeth grow 

 continually to compensate for wear, but 

 the enamel exends to the back surface 

 of the tooth. There is also an extra pair 

 of incisors, lacking the cutting edges, 

 right behind the upper, front, two chisel 

 teeth. The jaws of lagomorphs are so fas- 

 tened that they chew with a sidewise mo- 

 tion, while in rodents there is consider- 

 able longitudinal action. 



A good name for the hoofed mammals 

 might be "toenail walkers," for the hoof 

 is actually a specialized toenail. Yosemite 

 deer and bighorns, or mountain sheep, 

 usually walk on the two large toenails 

 on each foot and are therefore members 

 of the tven-toed, hoofed order of mam- 

 mals, Artiodactyla. 



