Experimental study of residency and emigration in house mice

Abstract

I used enclosures with exits for emigration to test whether house mice could regulate their numbers by emigration to two levels of resources. Exits had a water obstacle likley to be crossed only by true emigrants. Enclosures had excess food and water and the number of shelters was held constant. I introduced a pair of mice into enclosures about every other night, until no more would become residents. I ran 7 trials in single enclosures and 8 in double enclosures (2 single enclosures joined with a tunnel). The number of mice that stayed within a given size enclosure was consistant, and was 2.3 times higher in double enclosures than in single enclosures. Weather, predation, starvation, and disease did not act in any trials. My data support the contention that house mice can control their population numbers through spacing and emigration.