Supplemental feedings

A 0.5 ha bluegrass study site was supplementally fed from June 1977 through December 1983. An adjacent 0.8 ha bluegrass site, separated from the supplementally fed site by a 15 m closely mown area, served as the control (Getz et al. 1987). These were the same sites utilized by Cole & Batzli (1978) from May 1975-November 1976. A 0.5 ha tallgrass site at the east end of the tallgrass prairie in Phillips tract (Getz et al. 2001) was supplementally fed from September 1977 through May 1987. A similarly sized site at the west end of the prairie, 150 m from the supplementally fed site, served as the control. Both M. ochrogaster and M. pennsylvanicus occurred in the supplementally fed and control sites through May 1984. From September 1984 through March 1987, M. pennsylvanicus were removed from both the supplementally fed and control sites in tallgrass habitat.

Feeding stations, consisting of 0.5 liter glass bottles, were placed at each trapping station. Purina rabbit chow (No. 5321), a high quality diet for both M ochrogaster and M. pennsylvanicus (Cole & Batzli 1979), was used as supplemental food. The bottles were checked twice weekly and refilled as necessary to ensure food was present in them and in good condition at all times.

Interspecific interaction. We examined the effects of one species on the other in bluegrass and tallgrass. All M. ochrogaster were removed from a 1 ha bluegrass site from May 1977 through May 1987. M. pennsylvanicus were removed from another 1 ha bluegrass site from May 1977 through May 1997. Because M. ochrogaster populations were very low and M. pennsylvanicus very high most of the time in tallgrass, only effects of M. pennsylvanicus on M. ochrogaster were tested in tallgrass. We removed M. pennsylvanicus from a 0.5 ha tallgrass site at the west end of the Phillips tract tallgrass prairie from September 1984 through May 1997. From January 1981 through November 1983, M. pennsylvanicus also were removed from a 0.67 ha tallgrass site in Trelease prairie (Getz et al. 1987). Removed animals were released on the opposite side of an Interstate highway, approximately 1 km from the study sites.

We compared population density, survival, persistence of young, proportion of reproductive females, and number of immigrants in the sites where each species was alone with the sites where both species were present.

We also utilized the 25-yr data set to test for correlations between population density of one species and population density, monthly survival rates, persistence of young, and proportion of reproductive females of the other species. Detailed analyses were limited to bluegrass because M. ochrogaster was either absent or in very low numbers most of the time in tallgrass. Even in bluegrass, each species was often absent or at very low densities for extended periods of time and thus we conducted additional analyses limited to periods when population densities of the potentially “suppressing” species were at or above the 25-year mean for bluegrass: M. ochrogaster, 18/ha; M. pennsylvanicus, 14/ha (Getz et al. 2001). Effects of M. ochrogaster on M. pennsylvanicus in tallgrass were examined for the few periods during which densities of M. ochrogaster were above the 25-yr mean for tallgrass (8/ha).

This folder includes the listing of files from study sites that were supplementally fed and the controls for those sites/times.

The actual data files are not repeated in this folder. They may be accessed from the list of original field records or the compiled files.

Supplemental feeding sites:

Bluegrass Supplemental fed site: MO 08 and MP 08
Control site: MO 07 and MP 07

Tallgrass Supplemental fed sites: MO 17 and MO 19; MP 17
Control sites: MO 15 and MO 19; MP 15

See list of study sites for exact dates to use.