Demography and reproduction in island and mainland white-footed mice (Peromyscus leucopus) in southeastern Massachusetts

Abstract

Demography and reproduction of white-footed mice (Peromyscus leucopus) were studied on Muskeget Island and mainland southeastern Massachusetts. Both populations displayed similar trends in density with annual peaks every autumn or winter and lows every spring. Peaks in the two populations were similar, but the mainland population maintained a higher average density. Survival rates on Muskeget were very poor and could be attributed to a high level of transiency (or failure to attain residency). Once residency was attained, loss rates were similar on Muskeget and the mainland. Male residents in both populations had higher loss rates than females. Mainland mice adjusted reproductive effort in a manner similar to populations that are intrinsically regulated. Muskeget mice, however, did not adjust reproductive effort in a manner consistent with self-regulated populations. We suggest that the mainland population was at or near a hypothesized threshold in numbers where males limit densities by their aggressive behavior toward juveniles. The mainland mice had more characteristics of a K-selected population than the island mice. This result is expected when an intrinsically regulated population is compared with one that is not self-regulated.