EARLY MALNUTRITION INCREASES EMIGRATION OF ADULT FEMALE MEADOW VOLES, MICROTUS-PENNSYLVANICUS

Laboratory mice and rats malnourished as infants through food restriction or reduced protein/calorie diets show increased activity and aggressiveness as well-fed adults. Dispersal behaviour, which affect population dynamics, and result in the colonization of new habitats, is thought to be associated with high levels of activity and aggressiveness. In this study experimental meadow voles received a standard laboratory diet diluted with two parts by weight starch from birth to 6 weeks of age and were then given a standard laboratory diet including alfalfa hay. Control voles always received the standard laboratory diet including alfalfa hay. During the period of starch diluted diet the experimental voles grew at approximately half the rate of control voles. At 30 weeks of age or older, control and experimental meadow voles were released in a predator free outdoor enclosure situated in good habitat. Experimental females entered exit gates and were caught in traps outside the enclosure fence significantly more often than control females. Thus, the nutritional history of female voles appears to be an important determinant of their emigration.