Seasonal roadside ditch use by Microtus and Sigmodon.

Abstract

During late fall and winter, rural roadside ditches support numerous small mammal species regardless of the type of adjacent habitat. The extent of ditch utilization as small mammal winter habitat is influenced by the effect of agricultural use of adjoining land and by factors associated with competition, predation and weather. This two year study examined the use of Microtus ochrogaster and Sigmodon hispidus of ditches and adjoining agricultural land, marginal pasture, and native grassland. Vegetative cover in all ditches studied remained relatively constant during the study, except for the native-grassland ditch (ditch R) which was burned the first spring. Where ditch and adjacent area vegetative cover were homogenous and constant (ditch R), separate rodent populations appeared to be established in the ditch and on the adjoining land. Where agricultural treatment of adjoining land resulted in cover that varied with season of the year, evidence suggested that roadside ditches may represent primary habitat with adjacent land serving as forage and dispersal areas for ditch populations. However, some use of ditches for winter habitation by a small number of rodents from the adjoining lands was indicated.