Dynamics in an Ecologically Isolated Population of the Brush Mouse

A live-trap study of the brush mouse, Peromyscus boylii attwateri , was conducted on an ecologically isolated cedar glade in the Missouri Ozarks. Population density varied from a high of 2.17 per acre in December 1961 to a low of 0.28 mouse per acre in August 1962. This decline appeared to result from a reproductive failure in the females coupled with a normal mortality rate of resident mice. The failure of females to produce young during this breeding period could not be related to any obvious environmental or population condition. The survival rate at 4-month intervals (for 16 months) of 15 mice marked in August 1961 was 66.7%, 40.4%, 13.3% and 6.7%, respectively. The estimated mean life-span of 39 mice was 6.8 months and the estimated maximum life-span was 18.0 months. The absence of egress from the cedar glade by members of the population was deemed the significant factor in revealing the rather high survival rate and long life-span of brush mice. The average home range of adult brush mice was 0.49 acre. The home ranges of males averaged almost twice as large as those of females. Home ranges invariably had an elongated axis which coincided with the horizontal and parallel outcrops of dolomite which were present.