Movements and Populations of Opossums in a Cultivated Area

Abstract

Because studies of movements and populations of opossums (Didelphis marsupialis) have usually been conducted where trees and shrubs were the predominant vegetation on a substantial part or all of the land, it was believed that a similar study of opossums in an intensively cultivated area would provide useful comparative information. The possibilities for study of opossums in such areas apparently have been neglected. During a study of sylvan rabies in carnivores (National Institutes of Health Grant No. E-1349) in northwestern Illinois, opossums livetrapped on a 6-square-mile study area in Carroll County were marked and released at their respective sites of capture. Records were kept of dates and locations of all captures and recaptures. About 98 percent of the land on the study area is under cultivation, with approximately 51 percent of the area in corn, 29 percent in tame hay, and 18 percent in oats. The only trees on the area other than those in farmyards are a few scattered willows (Salix sp.) along small streams, and an occasional osage-orange (Maclura pomifera), box elder (Acer negundo), or cherry (Prunus sp.) along fencerows. The nearest woodlots of any consequence are more than 3 miles from the periphery of the study area. Sixty-five captures involving 38 opossums were made during May through October, 1959 through 1961. Twenty-five opossums were caught once each; eight, two times each; two, three times each; one, four times; and two, seven times each. 127