Demography of the western harvest mouse, Reithrodontomys megalotis, in eastern Kansas.

Reithrodontomys megalotis was live-trapped on three open field grids in eastern Kansas from August 1979 to August 1982. One grid was a control on which normal demography was monitored, and two were experimental grids where periodic removal of residents allowed the investigation of the demographic and fitness consequences of emigration. Popullations on the control grid showed an annual cycle in numbers, reaching peaks in density during the winter of each year, falling to low densities during the summer. Low summer densities were attributed, at least partially, to low trappability of R. megalotis during periods of high resource abundance. Reproduction was initiated in the spring of each year at approximately the same time as the emergence of new vegetative growth, and ceased in late fall of each year. The trappable population was composed almost entirely of adults, and the sex ratio was skewed significantly toward females. A statistically significant negative association between the number of M. ochrogaster residents and the reproductive activity of female R. megalotis residents was found. A canonical correlation analysis revealed a common seasonal component to the demography of the two species, and possible interspecific affects. Emigrating R. megalotis were a nonrandom sample of the population, with emigrants more likely to be subadult and juvenile males when compared to residents. No association was detected between the numbers of M. ochrogaster colonizing the removal grid and the numbers of R. megalotis colonizing the same removal grid, or between the number of M. ochrogaster residents on the control grid and the numbers of R. megalotis colonizing the removal grids. However, the number of R. megalotis residents on the control grid is positively correlated with the number of R. megalotis on the removal grids.