254 ECONOMIC ZOOLOGY 



Another more expensive method, that may be used to kill any 

 animals, that may escape the poison, is to suffocate them in their bur- 

 rows with a gas, preferably carbon bisulphid. A tablespoonful of the 

 crude liquid is poured on a corncob, a piece of dried horse manure or 

 some other absorbent substance and is thrust as far as possible in the 

 hole, just as is done for killing rats in outdoor burrows, and the hole is 

 closed with dirt. If properly done it will kill every squirrel in the bur- 

 row, provided all the holes are closed; this method is best used during 

 wet weather when the gas cannot so well escape through pores in the 

 earth. Figure 160 shows a number of squirrels killed by poisoned barley, 

 used while still in the head. Buzzards eat the poisoned squirrels ap- 

 parently without being injured by the poison. 



Under some circumstances traps can be used to advantage in squir- 

 rel campaigns, probably the strong guillotine traps mentioned and 

 figured in connection with rats being the best. 



Where only a few animals are present they may be shot with rifles 

 or shot-guns; in this case the animals, especially the young, may be 

 used for food, though there is danger, in some cases from handling 

 them, on account of the bubonic plague. 



As in the case of field mice there are numerous animals that serve 

 to check the increase in numbers of the ground squirrels and the de- 

 struction by man of these natural enemies will result in an increase in 

 the numbers of the pest. Among these animals are the golden eagles, 

 coyotes, foxes, badgers, bobcats, etc. 



Planted corn may be protected from ground squirrels and some 

 other animals by coating it with coal tar. 



Rabbits. More than two dozen species of rabbits occur in North 

 America; they fall rather naturally, according to size and habits, into 

 two groups: the larger forms (genus Lepus), including the jack rabbits, 

 snowshoe rabbits, etc., are found mostly west of the Mississippi. The 

 smaller forms (genus Sylvttagus), generally called " cottontails " occur 

 in all of the States of the Union, Fig. 161. 



Rabbits raise from two to four litters a year with an average of four 

 per litter, the rate of breeding varying with the species. They are, as 

 adults, strictly vegetarian, and while they prefer certain foods they 

 will when hungry eat practically any kind of vegetable matter. Since 

 they often do very serious damage to truck gardens, melons, clover, 

 alfalfa, fruit, and nursery trees, etc., their repression is sometimes an 



