BUREAU OF BIOLOGICAL SURVEY. 431 



Pocket-gopher campaigns in Idaho include work in eight counties, 

 where more than 1,650 quarts of bait were used on about 78,000 

 acres and considerable trapping was done in connection with the 

 poisoning operations. 



JACK BABBITS. 



Great fluctuations in numbers characterize the occurrence of jack 

 rabbits throughout their range. Relatively little work against them 

 has been required during the past year. The very extensive poison- 

 ing and driving campaigns which were conducted in Idaho, Oregon, 

 and Washington during the fiscal year 1922 resulted in such a 

 marked reduction in their numbers that little damage has been 

 reported since. 



In Nevada, where serious damage has been done from time to time 

 and extended poisoning campaigns have been conducted with good 

 effect, it has been reported that jack rabbits were destroyed in large 

 numbers by a disease and that they did relatively little damage. In 

 Utah 334,000 jack rabbits are reported killed as a result of the 

 campaigns which were conducted. 



In limited campaigns organized in four counties in Idaho about 

 6,100 pounds of poisoned bait were used on 51,000 acres, and a few 

 drives were also conducted. In Kansas, Montana, and Texas it is 

 reported that jack rabbits are on the increase, and as considerable 

 damage is being done locally, interest is awakening in the inaugu- 

 ration of control measures. Wliere these animals occur in large 

 numbers they are capable of doing serious damage to growing crops, 

 range grasses, meadows, hay in stacks, and to orchards and vine- 

 yards, but methods for destroying them on a large scale have been 

 found. 



MEADOW MICE, PINE MICE, POCKET MICE, AND KANGAROO KATS. 



Under favorable conditions the various kinds of native mice be- 

 come excessively abundant locally, and, although small in size, col- 

 lectively they do serious damage in orchards, gardens, and truck 

 farms. During the previous year meadow mice appeared in de- 

 structive numbers in many of the important orchard sections of 

 Idaho and Washington. Where these were foreseen in time the use 

 of poisons recommended by the bureau prevented serious damage, 

 but in many localities where such action was not taken the loss in 

 trees was heavy. This situation emphasized the importance of fore- 

 si o-ht in dealing with local outbreaks of these small rodents. 



^During this year such outbreaks of orchard mice occurred in 

 Yakima,'^Chelan, Okanogan, Grant, Douglas, and Kittitas Counties, 

 in Washington, and necessitated control measures. A questionnaire 

 sent to orchardists showed that in Yakima County 292 growers 

 reported 4,598 trees girdled during the previous winter. In Chelan 

 County a loss of 900 trees was reported. As the trees are from 1 

 to 15 years old, and valued at from $5 to $100 each, the importance 

 of controlling the mice is evident. A general poisoning campaign 

 was started the 1st of November, which is a very favorable time. 

 Steamed-rolled oats proved a most satisfactory carrier of the poison. 

 In this campaign 19,600 acres of orchard land were treated by more 

 than 1,400 cooperators. 



