FOOD AS A CONTROL OF A POPULATION OF WHITE-FOOTED MICE, PEROMYSCUS LEUCOPUS NOVEBORACENSIS (FISCHER)

Mice were introduced to an island before and after food was supplied in excess of food consumed. The population of mice on the experimental island with food in excess is compared with populations of mice on the same island before the addition of food, on an adjacent island, and on the mainland. Before food was supplied in excess, death rate (death and dispersal) greatly exceeded birth rate and the population failed. After food was supplied in excess death rate of the second introduction decreased and population increased to greatly exceed the density of mice on the control island.The increased density of mice on the experimental island is the result of a decreased death rate, particularly in mice from birth to approximately 1 month of age. Increased birth rate may also be a factor. Food supply regulates the abundance of white-footed mice by affecting death rate and possibly birth rate. The most important effect of food supply is on the survival of young from birth to approximately 1 month of age.Evidence that intraspecific strife for space occurs in relatively dense population is presented. Intraspecific strife for space may regulate population of mice beyond the level of abundance determined by the supply of food.