Population Characteristics of Peromyscus gossypinus and Sigmodon hispidus in Tropical Hammocks of South Florida

This is the authors' abstract. We don't add key points for this paper.

Population data were recorded on tagged Peromyscus gossypinus and Sigmodon hispidus trapped on study grids in two tropical hammocks of South Florida. Densities of cotton mice, the dominant species, appeared to be related to successional stages of habitat with greater numbers found in mature tropical hammocks (27 to 96 animals per hectare). Populations decreased in summer and autumn and increased in the winter and spring with recruitment of immature animals. Breeding persisted from August through May peaking in the winter and early spring. Females averaged 3.1 mice per litter with some producing three to four litters per year. Highest mortality occurred during the first 6 months. The population turned over completely every 18 to 20 months. Cotton rats, normally inhabitants of the sawgrass marsh, frequented portions of the hammocks throughout the year. It appeared as though females used the hammocks as nurseries during the summer. Period of greatest interaction between the two species in tropical hammocks is between March and November when the water levels rise. Dispersion patterns of cotton mice do not appear to be greatly influenced by the presence of cotton rats. Sex ratios, age composition, parasites, reproduction, longevity and population turnover, and movements of both species are discussed.