Behavior of a Population of Forest-Mice When Subjected to Poison

Abstract

A belt of Douglas-fir fronting the inland border of the north coast redwoods comprises the last great stand of virgin timber in California. Not previously-exploited because of ruggedness of the mountains on which it grows, it is yielding now to the logging truck and caterpillar tractor. A timber rush is on. Within two or three decades little of the old forest will remain (Pine, 1953; Vaux, 1955). As a rule, natural reproduction of conifers in the region is not sufficiently vigorous to replace timber removed by logging or destroyed by fire. Compared with the Douglas-fir belt of Oregon and Washington, environmental conditions in northern California are severe. The dry season is long and intense, and tan oak, which sprouts aggressively when felled or burned, often captures denuded land. The answer to the problem of reforestation might be direct (artificial) seeding except for the presence of small mammals which are adept at finding and devouring coniferous seed. White-footed mice ( Peromyscus maniculatus and P. truei ), abroad only by night and inconspicuous out of proportion to their numbers, are the chief offenders. The diurnal and more obvious chipmunks ( Eutamias townsendii ) are of secondary importance, and shrews ( Sorex trowbridgii ) and red-backed mice ( Clethrionomys occidentalis ) are relatively scarce. The recommended method of dealing with seed-eating rodents of the forest is to poison them (Eadie, 1954). In theory, foresters can wipe out a population of wild mice with lethal baits, then sow seed in the autumn and have a dense stand of seedlings after germination occurs in the following spring. But every attempt to protect seed by killing rodents with cereal baits in the California Douglas-fir region has failed. Assuredly a rodenticide such as sodium fluoroacetate, commonly known as Compound 1080 (Kalmbach, 1945), is exceedingly effective when first applied. It can decimate a population …