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Although fires are an integral part of prairie ecology (Bragg and Hulbert 1976, Daubenmire 1968, Rice and Parenti 1978, Zimmerman and Kucera 1977), there is evidence that mowing can serve at least some of the functions of fire (Hover and Bragg 1981) in prairies. Mowing, in fact, has two major advantages over burning. First there is no need for large crews to control the fire, and second the hay produced can be used as a cash crop. Because mowing is an attractive alternative to burning for prairie preserves it is important to determine the effects of mowing on the prairie. In this paper we report our findings on the effects of mowing on the community of rodents in a natural tallgrass prairie near Lincoln, Nebraska. Although there has been some work on the reaction of rodents to prairie fires (LoBue and Darnell 1959, Tester and Marshall 1962, Schramm 1970, Cook 1959, Moreth and Schramm 1972), not much work has been done on the effects of mowing (LoBue and Darnel1 1959, Tester and Marshall 1962). The general finding from burning and mowing in the tallgrass prairies of North America is that populations of Microtus decline dramatically after the removal of the vegetation, and the numbers of Peromyscus maniculatus increase. The populations of rodents return to pre-fire levels as the vegetation above ground grows back. Even though mowing and burning have similar effects on aboveground material, there are differences. First, mowing leaves a stubble of vegetation, and second, mowing is typically done on a yearly basis, in the late summer or early fall. The result of yearly mowing is that fields are left as stubble for long periods of time every year, and it is not known whether this cover is sufficient to maintain the population of Microtus at high density. Our results indicate that mowing, like burning, greatly reduces the use of an area by Microtus and increases the density of P. maniculatus until the grass can grow back. Depending on the rate of growth of the grass this process can take more than a year. If the prairie is mowed every year to maximize the production of hay, populations of Microtus cannot be maintained at high densities.