CHAPTER IX. 



THE RODENTS, OR GNAWING ANIMALS. 



T 



HE Rodents, or Gnawing Mammals, have all the 

 same general type of teeth, from which the order 

 receives its distinctive name. There are a very 

 large number of families and of genera among the 

 rodents, more than in any other order of mammals. 

 All the rodents possess a pair of long chisel-shaped 

 incisor teeth in each jaw. The ends of these teeth 

 are worn into a sharp edge which cuts like a steel- 

 tool. In most rodents these are the only teeth in- 

 that part of the jaw, a wide gap intervening between 

 them and the other teeth. The hares, rabbits, and 

 calling-hares have a minute pair of teeth set just 

 behind the large pair in the upper jaw. The grinding- 

 teeth are set far back, and are never more than six 

 in number, these being sometimes reduced to four. 

 Rodents generally have five toes on the fore feet; in< 

 the hind feet there are in some cases only four, or 

 even three. None of the species are of great size; 

 the largest, the CAPYBARA, a water-living animal of 

 South America, is about the dimensions of a small 

 pig. But the number of species of small rodents is 

 prodigious, and 

 their fecundity so 



great that they ^^ 



constantly increase 

 in favourable 



seasons until they become a plague. Voles, lemmings, field- 

 mice, and rabbits are constant sources of loss to agriculture 

 in their seasons of extraordinary increase. Most rodents feed ^K. l 



on vegetables, though rats and mice have developed car- 

 nivorous tastes. No rodents have canine teeth. 



Photo ly W. P. Dando] [Regent's Park. 



CAPYBARA. 



This, the largest of the Rodents, is found by the rivers of 

 South America. 





THE SQUIRRELS. 



Those of the order of Gnawing Animals which have only 

 two incisors in each jaw, and no rudimentary teeth like 

 those possessed by the hares, are called "Simple-toothed 

 Rodents." Of these the family usually placed first in order 

 is that of the SQUIRRELS and their allies. The True Squirrels 

 and Marmots have five molar teeth on each side of the 

 upper jaw. 



Squirrels are found in nearly every temperate part of 

 the globe, from Norway to Japan, and in very great numbers 



146 



Jiy permission of Professor Bumpus, At- 1'urk. 



FLYING-SQUIRREL. 

 One of the small species of the group. 



