The bait materials that are used are selected because they are not 
readily taken by other animals. The clean bait studies are always made first

to determine the degree of acceptance by the rodent pest and the degree of

rejection by other animals. Barley (whole or potted) is used as the bait

for ground squirrel control in California because it is well accepted by

rodents and not readily by birds. The same is true of steamed rolled oat

groats. Tests under caged conditions and in the field on acceptance are 
always raade in detail. 
The selectivity of a poison method&is not based entirely on the bait

used but equally as much on the manner of exposure. The rodent normally 
feeds one place and the bird another place. Only occasionally does a bird

feed on the clean hard surface about the entrance to a ground squirrel burrow*

Rodents readily pick up grain there. 
The meadow mice (Microtus sp.) that girdle and destroy orchard trees 
do not feed in the open spaces. Poison bait for them is placed under cover

which may be a forkful of hay, an old sack, a piece of asphalt roofing paper,

or a board. This protects it from other animals and is selective for meadow

or pine mice. 
The placement of a poison station can be made very selective for the 
coyote. Its line of travel is generally along and across a ridge in such
a 
way that the station can be placed out of line of regular travel of the fox,

skunk and other animals* 
After carefully observing in the field the natural habits of the mammals

requiring control, certain small differences in feeding or living habits
can 
be utilized which make the method of control quite selective. This observation

is one phase of the regular research studies in devising ways and means of
con- 
trolling animals. 
 
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