MAMMALIA 



253 



pest but, owing to a lack of cooperation among adjacent landholders, 

 they are often not as effective as they should be. 



The animal breeds once a year, with from five to eleven in a litter, 

 and though it is a much less rapid breeder than the brown rat it soon 

 multiplies when not actively fought. A hundred or more may some- 

 times be in sight at one time, in an active colony. 



Perhaps the most effective method of destruction is by means of 

 poisons, of which strychnine is to be recommended. Grain is coated 

 with strychnine, as described for killing field mice, and this poisoned 



PIG. 1 60. Ground squirrels, Citellus beecheyi, killed by poisoned green barley heads 

 at mouth of burrow. (From Merriam, The California Ground Squirrel.) 



bait is scattered about the holes and runs, preferably during the dry 

 season; the animals are thus killed in large numbers. As a protection 

 for birds barley is recommended, the squirrels eat it readily and birds 

 very seldom do. It was found that it was better to use grain that had 

 been merely coated with the strychnine rather than soaked in it, be- 

 cause the cheek pouches, in which the grain is carried, are more quickly 

 susceptible, to poison than is the stomach and the food does not have 

 to be eaten before the animal is killed. The cost of poisoning in this 

 way varies, of course, with the cost of the materials and the labor but 

 it is only a few cents an acre, since 100 pounds of the grain will be 

 sufficient for 200 to 300 acres. 



