Experimental Zoogeography: Introductions of Mice to Small Islands

Abstract

Microtus pennsylvanicus is the only rodent native to small islands in the Gulf of Maine. Peromyscus maniculatus is found on larger islands, even when rather remote, while Clethrionomys gapperi occurs only on the largest islands within 1 mile of the mainland. Population dynamics and rates of extinction and recolonization of resident Microtus populations were studied from 1962 to 1972. During this period, the ability of Peromyscus and Clethrionomys to establish and maintain insular populations was tested through experimental introductions of from one to eight pairs. Empirical determinations of demographic parameters provide data consistent with the MacArthur-Wilson model for propagule survivorship, and propagule sizes are of the same order of magnitude as those predicted by the model. Average survival (T1) of propagules and time to ultimate extinction (TK) of established populations of the three species also agree with theoretical expectations. The distribution of the three species in the Gulf of Maine is l...