NOTE.--This bulletin, a joint contribution of the Bureau of Biological
Survey and the Arizona Agricultural Experiment Station, contains a
summary of the results of investigations of the relation of a subspecies
of kangaroo rat to the carrying capacity of the open ranges, being one
phase of a general study of the life histories of rodent groups as they
affect agriculture, forestry, and grazing.




IMPORTANCE OF RODENT GROUPS.


As the serious character of the depredations by harmful rodents is
recognized, State, Federal, and private expenditures for their control
increase year by year. These depredations include not only the attacks
by introduced rats and mice on food materials stored in granaries,
warehouses, commercial establishments, docks, and private houses, but
also, particularly in the Western States, the ravages of several groups
of native ground squirrels and other noxious rodents in grain and
certain other field crops. Nor is this all, for it has been found that
such rodents as prairie dogs, pocket gophers, marmots, ground squirrels,
and rabbits take appreciable and serious toll of the forage on the open
grazing range; in fact, that they reduce the carrying capacity of the
range to such an extent that expenditures for control measures are amply
justified. Current estimates place the loss of goods due to rats and
mice in warehouses and stores throughout the United States at no less
than $200,000,000 annually, and damage to the carrying capacity of the
open range and to cultivated crops generally by native rodents in the
Western States at $300,000,000 additional; added together, we have an