A PLAGUE OF MICE 



483 



found. Although alfalfa was already 

 well grown, furnishing the mice abun- 

 dant food, by systematic poisoning, 

 under the direction of the Biological 

 Survey men, they were so effectively 

 reduced in the infested areas as not to 

 be dangerous again during the season — 

 in other words, a plague was averted. 



The results actually obtained here 

 prove that mouse plagues can be checked 

 It takes several seasons to produce a 

 general plague of mice, and damage is 

 noticeable for at least a season before a 

 serious outbreak occurs. Though nat- 

 ural agencies may be depended upon to 

 overcome such abnormal numbers finally, 

 yet, unless active repressive measures are 

 taken, enormous damage to crops will 

 result. Control, easy at first, becomes 

 more and more difficult as the mice in- 

 crease in numbers, and, after a plague is 

 well established, is very expensive. 



In Humboldt Valley, in the beginning, 

 a little poisoning with green alfalfa or 

 crushed wheat would have sufficed to 

 prevent the plague. During the fall and 

 winter of 1906-07, when the mice se- 

 riously injured fields here and there, they 

 could have been destroyed with poisoned 

 alfalfa hay. Even during the summer of 

 1907 concerted and vigorous poisoning 

 would have destroyed them at a cost 

 small indeed in comparison with the 

 damage they inflicted later. 



HAWKS, OWLS, WEASELS, AND COYOTES 

 PROTECT THE FARMER 



Of the many remarkable features of 

 the mouse plague in Humboldt Valley, 

 none is of greater interest, or indeed of 

 greater significance, than the large num- 

 bers of birds and mammals which gath- 

 ered to feed on the mice. Under rows 

 of trees, about the bases of fence posts, 

 and scattered everywhere in the fields 

 were regurgitated pellets of mouse fur 

 and bones, affording abundant proof of 

 the services rendered by birds, while 

 many holes and destroyed nests in the 

 fields showed the work done by skunks 

 and coyotes. So apparent was the as- 

 sistance rendered by these creatures that 

 it attracted the attention and secured the 



Photo from Stanley E. Piper, U. S. Biological Survey 



THE MOUSE WHICH PRODUCED THE 

 PLAGUE IN NEVADA (MICROTUS 

 MONTANUS) 



protection of the farmers, many even 

 sparing the coyote, whose services as a 

 mouse destroyer deserve to be more 

 widely recognized. In Nevada coyotes 

 were frequently seen catching mice in 

 the daytime, and their droppings were 



