Seasonal Forage Availability in Relation to Energy Requirements of Pine Voles in Two Orchard Types

Results from previous work on pine vole populations and habitat interactions (Cengel et a1. 1978; Noffsinger 1976) suggested that pine vole populations were quite sensitive to seasonal changes in the quantity, species composition, and nutritive value of available forage. This conclusion was based on decreases in both reproductive performance and physical condition of pine voles collected from abandoned orchards in the fall as compared to voles taken from maintained orchards during the same season. Utilizing information from these investigations, a follow-up study was designed to investigate food availability and nutrient composition, food consumption, food digestibility, and energy requirements of pine voles. Results from this bioenergetic approach to studying pine vole populations, coupled with detailed knowledge of their population dynamics, should provide useful information for identifying critical or weak points in the ecology of populations as well as for assessing the effects of various management or control strategies applied to biological (orchard) systems. Data from this research on ecological energetics of pine vole populations will ultimately be included as part of an overall population energetics model which will be used for simulating both natural and man-induced habitat changes and predicting their effect on pine vole populations (Coyle & Tipton, unpublished). This paper summarizes the major points obtained from a bioenergetic study conducted during 1978 and 1979 in an orchard abandoned for 9 years and a maintained orchard, both located near Daleville, Virginia