Certain species of the rodents that in large numbers infest lands of
value for crop or forage production must be eradicated locally to
meet the requirements of agriculture and forestry. Those that figure
most largely in the cooperative control operations in one part or
another of their ranges are the prairie dogs, ground squirrels, pocket
gophers, jack rabbits, porcupines, and native and introduced rats and
mice. Other groups that locally become unduly numerous and destructive
may also on occasion come within the control program. It would be
impossible to eradicate everywhere the ground squirrels, prairie dogs,
and other rodents that range over vast areas of relatively worthless
lands, and such action is not desirable, even on the public domain. In
areas of economic importance, however, definite tracts are established
where the rodents can be kept under thorough control, and operations
are extended sufficiently to prevent reinfestation.