l^p!"!"!. } LIFE HISTORY OF THE KAISTGAEOO RAT. 37 



With two kangaroo rats to the acre (1,280 jjer square mile), there 

 would be 64,000 animals on the 50 square miles of the Range Re- 

 serve. If each rat stores 4 pounds of grass seeds and crowns and 

 other edible forage during the season (and in severe seasons we find 

 that more crowns are stored than under ordinary conditions), a total 

 of 256,000 pounds, or 128 tons, of edible forage are rendered un- 

 available to stock. In dry years it is probable that this amount of 

 forage would be of critical importance. Allowing 50 pounds of 

 food a day for each steer, the forage destroyed would be sufficient 

 to i^rovide for the needs of one steer for 5,120 clays, or for the needs 

 of 14 steers for one year. On a stock ranch the size of the Range 

 Reserve this might mean the difference between success and failure. 



It seems not unlikely, therefore, that during seasons of drought the 

 banner-tailed kangaroo rat, where it is abundant on the grazing ranges 

 of the Southwest, may be a factor of critical importance in relation to 

 forage production and carrying capacity. It must be remembered, 

 moreover, that the stored material consists largely of seeds, so that 

 this loss is of greater importance than would be the case were it 

 ordinary forage. .Some of the range grasses of this region found 

 in greatest quantity in the stored material depend in large part, 

 under certain conditions, upon seed reproduction. Rehabilitation of 

 a depleted range after severe drought and consequent close grazing 

 and trampling is retarded by the heavy toll of seed taken by the kan- 

 garoo rats. 



CONTROL. 



Kangaroo rats may be easily eradicated by the use of the poisoned 

 grain used for prairie-dog control by the Biological Survey and the 

 University of Arizona Extension Service. This can be obtained by 

 application to the State representative of the Biological Survey or 

 to the local county agricultural agent, or may be mixed as follows : 



Formula for poisoned iait. — Dissolve 1 ounce of strychnine sulphate in U 

 pints of boiling water. Add 1 heaping tablespoonful of gloss starch, previously 

 mixed with a little cold water, and boil until a clear paste is formed. Add 1 

 ounce of baking soda and stir to a creamy mass. Add ^ ounce of glycerine and 

 i pint of corn sirup and stir thoroughly. Pour over 16 quarts of rolled barle.v 

 and mix well until every grain is evenly coated. Allow to dry before using. 



In bushel quantities use as above directed, 2 ounces of strychnine, 2 ounces 

 of soda, 1 ounce of glycerin, 1^ ounces of starch, IJ quarts of boiling water, 

 and f pint of corn sirup. 



Scatter poison, when the natural food of the kangaroo rat is scarce, on clean 

 hard places near the holes, 1 quart to 50 holes. 



If powdered strychnine alkaloid is used, prepare the hot starch paste first. 

 Then sift strychnine and baking soda, previously thoroughly mixed, into the 

 hot starch paste and stir to a creamy mass. Proceed as in the above direc- 

 tions with sirup, glycerin, etc. 



