42 RODENTS OF IOWA 



garious, and some of the villages extend for miles while the num- 

 ber of inhabitants is very great. 



The burrows in which the animals live vary according to local 

 conditions. In arid regions the mounds are usually small ; but in 

 places where the rainfall is great, high mounds are necessary and 

 require the constant care and attention of the animals. Prairie- 

 dogs, except at high altitudes, do not hibernate, although they may 

 remain under cover for days during severe winter weather. They 

 may, however, appear above ground on fine days even though 

 the ground is covered with snow. In the extreme north, when 

 deep snow 'covers the villages for many weeks the animals remain 

 concealed for long periods. 



Prairie-dogs are attacked by a number of natural enemies among 

 which are the coyote, badger, eagle, black-footed ferret, and rough- 

 legged hawk. Although many stories) have been told concerning 

 the occupancy of a single burrow by prairie-dogs, burrowing owls 

 and rattlesnakes, careful observation shows that while all these 

 animals are often found together, the association is not of ad- 

 vantage to the prairie-dog, for many of its young are sacrificed 

 to the intruders. 



Control Measures. In many localities where the animals are 

 abundant various measures of extermination have been tried, 

 among the best of which is the use of poison-coated grain. A for- 

 mula similar to the one given below has been employed with ex- 

 cellent results in North Dakota and elsewhere and is equally ef- 

 fective in destroying Franklin's and the thirteen-lined spermo- 

 philes. 



Formula for poison preparation: 



1. Mix thoroughly 1 ounce strychnia sulphate (powdered) and 



1 ounce baking soda. 



2. Sift this into % pint thin hot starch paste and stir to a 



creamy mass. Make the starch paste by dissolving a table- 

 spoonful of dry gloss starch in a little cold water, then add 

 this to % pint of boiling water. Boil and stir constantly 

 until a thin paste is formed. 



3. Add % pint heavy corn syrup and stir thoroughly. 



4. Add % ounce saccharin (or sugar 1 pint) and stir thor- 



oughly. 



5. Pour poison solution over 15 quarts clean oats and mix thor- 



oughly so that each grain is coated. Prepare 24 to 48 

 hours before using. 



