Similarity of spring population densities of the island beach vole (Microtus breweri), 1972–1986

Abstract
The beach vole (Microtus breweri) population on Muskeget Island was intensively trapped from 1972 until 1977 and has been monitored annually since then. Using two criteria for cyclicity, we confirmed that the population is acyclic. The sex ratio did not deviate substantially from a 1:1 ratio. Twenty percent of animals had a forehead blaze. From 1972 to 1977, when trapped throughout the year, these values increased during the breeding season. For the year as a whole there were 1.33 male voles per female and a blaze frequency among the animals of 40.8%.