Population control in confined colonies of golden hamsters (Mesocricetus auratus Waterhouse).

The mechanisms by which confined colonies of Golden Hamsters regulate the density of their population were investigated. Six experimental populations were established with two males and two females each and allowed to grow freely for 3-8 months. At no time did any population exceed eight individuals. This appeared to be the result of a high rate of infant mortality due to failure of pregnant and parturient females to isolate themselves from the others. Two other populations were then established allowing many more nesting areas and more room for dispersal, but animals continued to crowd together and infant survival did not improve. These results contrast sharply with the large ultimate populations and only slowly developing disturbances seen in rats and mice. This difference in population control appears to be the direct result of a species difference in the tolerance of adults for strange newborns. In two further short-term experiments, the effects of the number and sex of adults in the founding population were systematically examined. The critical density at which no pups survived past the first day was six or more animals; females appeared to contribute more than males to infant mortality.