PARENT SESSION

HOUSE MOUSE DEMOGRAPHY: A CONTROLLED EXPERIMENT? Paul K. Anderson. Dept. of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.

ABSTRACT- Following Crew and Mirskia (1933) approximately 80 studies of confined Mus musculus populations have been published. At the time of peak interest in such experiments Southwick (1955) concluded that successful controlled experiments were improbable, due to individualistic behaviour of dominant males. To test this conclusion I designed an experiment based on the premises that expression of normal mouse behaviour and consequent population dynamics required (1) a spatially complex environment with abundant and dispersed resources and defensible nest sites and (2) simulation of emigration and predation. My experimental design was intended to duplicate, in manageable form, the high density mouse populations reported in stacks of un-threshed grain (Southern and Laurie 1946; Southwick 1958). Two eight-story population cages were constructed, each with 128 compartments, 48 nest boxes and 80 food and water stations. Cages were maintained in a temperature-and- light-controlled environment. Censuses took place at intervals of approximately 21 days and a predetermined density was restored at each census by random removals of weaned mice, making possible replicate measurements of the intrinsic rate of natural increase. Mean intrinsic rates of 0.009747 (Cage I, 8 replicates) and 0.009589 (Cage II, 7 replicates) were not significantly different. Data on several other demographic variables are presented, supporting the hypothesis that biologically realistic experimental design can make possible controlled experiments in house mouse demography.

KEY WORDS: populations, intrinsic rate of increase, Mus musculus, demography