EFFECTS OF MOOSE FORAGING ON BROWSE AVAILABILITY IN NEW HAMPSHIRE DEER YARDS

Abstract

Food habits of moose (Alces alces) and white-tailed deer (Odocoileus virginianus) overlap in northern New Hampshire during autumn and winter. High moose and deer densities in deer yards, where deer may be confined for extended periods, could result in competition for limited deciduous forage. The purpose of this study was to investigate possible impacts by moose on browse availability in deer yards, and the potential effects on deer. Fifteen deer yards were studied in northern New Hampshire during spring and fall, 1990-91. Unbrowsed and browse to deciduous twigs, and deer and moose pellet groups were counted on 900 permanent plots to measure seasonal browse use and population density of deer and moose. Twig biomass availability and removal were estimated for each season in all areas.

Combined data from all deer yards showed that unbrowsed biomass increased between spring 1990 and autumn 1990, and decreased between autumn 1990 and spring 1991. Moose browsed 7.2% of available food during autumn 1989 and winter 1990, 7.7% during autumn 1990, and 3.8% during winter 1991, accounting for 26.3%, 81.1%, and 17.6% of browsed biomass, respectively. One-year-old clearcuts adjacent to wintering areas were heavily browsed, particularly during the winter. Preferred moose foods during autumn work waking aspen and mountain maple. Pin cherry and nannyberry were removed relative to availability. Moose have the potential to substantially reduce the availability of preferred deciduous browse (e.g., maples) of deer, and thus reduce the carrying capacity of deer yards. Specialized management in areas of high moose density may be warranted where clearcuts adjacent to deer yards provide the essential winter forage of deer.