April, ’24] 
wade: calcium cyanide for prairie dogs 
341 
in open entrances, three being taken from one burrow. They had 
evidently gone in the evening after the treatment, which was about 
5:00 P. M. and were overcome by the gas, indicating that the effectiveness 
of the gas is maintained for several hours after the flakes are placed 
in the burrow entrances. 
August 29 the two dog towns were again visited and no live prairie 
dogs were seen and no signs of fresh work observed about any of the 
dens. The dogs were completely exterminated. 
A survey of the results obtained in 1922 showed satisfactory kills, 
where entrances to dens were left operii, with dosages of 1 to ounces 
per burrow. In the two tests made, May 5 and August 3 with 1 y 2 
ounces of calcium cyanide to the burrow, total kills were obtained 
and the*other tests made August 3 with ^ to 1 ounce to the dose was 
very promising with a kill approaching totality. In view of these results 
it was decided to continue the work in 1923 with a series of tests using 
a straight dosage of 1 ounce per burrow, in order to learn if this ap¬ 
parently minimum dose would be entirely effective. 
Date Area Dosage Entrance 
April 10, 1923 107 burrows 1 ounce Open 
April 10, 1923 250-300 burrows 1 ounce Open 
On April 14 one live dog and fresh signs around five or six dens were 
noted in the smaller town; in the second town no dogs were observed 
but there was some sign of their activities, and the owner of the farm 
said he had seen two dogs the day before. The kill in this experiment 
was considered to be about 99%. 
Another experiment was made as follows: 
Date Area Dosage Entrance 
April 12, 1923 48 burrows 1 ounce Open 
April 12, 1923 253 “ 1 “ 
April 12, 1923 271 “ 1 “ 
At the time these towns were treated many of the females were 
suckling young but as yet the young apparently were too small to leave 
their nests since none were seen above ground. On May 19 all three 
dog towns were checked. In the first town no dogs or signs could be 
seen which indicated a total kill; in the second town three or four old 
dogs were in evidence and a number of young; in the third town a 
number of old dogs were seen with a fair sized population of emaciated 
looking young crawling about in search of food. It was concluded 
that, at the time the burrows were treated, some of the young must have 
been about ready to leave their nests but did not, until forced by starva- 
