Immigration and emigration as contributory regulators of populations through social disruption

Abstract

Previously isolated mate laboratory mice were placed into groups of 16 mice per cage. Each day for 10 days, one animal was exchanged for another between two of the groups in a simulated balanced emigration–immigration. The animals in the third groups served as controls. Stress indicator organs were weighed to determine the effect of the balanced movement and the ensuing social disruption. Splenic and adrenal hypertrophy was greater in the mice exposed to movement than in the controls. Variance of hypertrophy followed the same pattern. Testicular development and size of seminal vesicles was greatly inhibited in the mice exposed to movement. Reproductive potential may be influenced by immigration and emigration through social disruption alone, with no change in actual available space, food, and other factors on a per animal basis.