An Ecological Study of the Fulvous Harvest Mouse in Eastern Texas

Abstract

Populations of fulvous harvest mice, Reithrodontomys fulvescens, were studied on three areas in Nacogdoches Co., Texas. One area in a pine forest and another in a grass-pine plantation provided comparative population data from 1955-1963. Data secured from the third area, located in a grass-pine ecotone, were useful in determining microhabitat distribution and movements of the differcnt sex and age groups. Fulvous harvest mice occurred predominantly in grassland, pinegrass ecotone, and grass-brush habitat. They were significantly absent from pine-type habitat, possibly because this habitat was occupied by cotton mice, Peromyscus gossypinus, and golden mice, Ochrotomys nuttalli. Fulvous harvest mice were most abundant in winter and to a lesser extent in summer. Peak populations occurred in 1957 in the grass-pine plantation and in 1958 in the adjacent pine forest. The exclusive boundary strip method of analysis of trap range data revealed that harvest mice range over approximately one-half acre. Females had a slightly larger trap range (= home range), .59 acre, than did males, .47 acre; young females averaged greatest linear movements. Neither sex displayed marked territorial behavior. Actual and estimated densities revealed approximately three fulvous harvest mice per acre in the pine-grass ecotone area (probably the optimal area of the three for these mice). There were slightly more males than females on all the areas studied. On the pine-grass ecotone, there were significantly greater numbers of adult males than adult females. Two principal breeding peaks, one in March and a second in July, were detected. Fulvous harvest mice seemed extremely tolerant of one another when confined under laboratory conditions. Mice born in captivity became independent of the female at approximately 3 weeks (the time of weaning). Under controlled laboratory conditions, captives displayed an activity rhythm seemingly correlated to the onset of dark periods. In the absence of well-defined light-dark cycles, activity occurred at times of natural darkness.