RODENTIA 251 



Washington, jack rabbits were also increasing rapidly, questions 

 die efficacy of mammals in the control of rodents. He says: "While 

 there is no doubt that predatory mammals are a factor in controlling 

 rodents, yet they play but a small part in maintaining the natural 

 balance. Larger factors are involved, and these include seasonal con- 

 ditions, fecundity of species, the acts of man in providing abundant 

 food, and the presence of natural and other shelter. On the other hand, 

 rodents the size of ground squirrels, or smaller, are more effectively 

 decreased in numbers by raptorial birds than by predatory mammals. 

 The quantity of rodent remains found in the stomachs and disgorges 

 of individual owls is almost unbelievable." 19 It is probable that during 

 ordinary times the combined efforts of predatory mammals and birds 

 are very important in keeping the rodents within reasonable bounds, 

 but when abundant food and shelter, favorable weather and other 

 conditions greatly increase the fecundity and average span of life of 

 such prolific breeders as mice, rabbits and prairie-dogs, they are likely 

 to get beyond control. In such cases birds, moving about very freely, can 

 more easily concentrate on infested areas where they may find abun- 

 dant food. Meantime, as has been said before, man, having by culti- 

 vation of crops provided more abundant food and better shelter for 

 the rodents, must assume complete control and resort to poisoning and 

 other methods. 



That badgers, because of their ability as diggers, may be at times 

 a very important factor in the control of burrowing rodents, is gen- 

 erally recognized. In Colorado they cleared the prairie-dogs from an 

 area a mile and a half long in a gulch, a large percentage of the 

 prairie-dog burrows having been excavated by the badgers. 20 It has 

 been said to be the habit of badgers to clear up one locality and then 

 when the rodents become too scarce to furnish them with food they 

 move on to another locality, whereupon the locality they have aban- 

 doned becomes again infested, unless precautions are taken to prevent 

 it. 



A faint notion of the damage done to crops by rodents may be ob- 

 tained from the following account of the meadow mouse, extracted 

 from Science Nezvs Letter of July 20, 1929. 



The meadow mouse looks soft and pretty and harmless, but he is a most 

 expensive guest just the same. Vernon Bailey, of the U. S. Biological Survey, 

 has been figuring his board bill, with rather startling results. A meadow mouse 



"Couch, Relationship of predatory mammals and birds of prey to rodent life, 

 Journ. Mammalogy, ix, 73-74, 1928. 



30 Silver, Badger activities in prairie-dog control, Journ. Mammalogy, ix, 63, 1928. 



