DIET SELECTION BY ALASKAN MOOSE DURING WINTER: EFFECTS OF FIRE AND FOREST SUCCESSION

Abstract

We studied forage available to and used by Alaskan moose (Alces alces gigas) during winter 1988-1989 on the Kenai Peninsula, Alaska, USA, to test the hypothesis that changes in the quality and abundance of browse during winter affected the selection of diet. Random plots were located in 3 age classes of vegetation (7-10, 20-30, and 70-80 years since the last fire)m which varied in abundance and quality of browse. Dominant species of browse we studied on those seral stands included scouler willow (Salix scouleriana), Kenai birch (Populus trichocarpa). We made twig counts of current annual growth in early (December), mid- (February), and late (April) winter to determine amounts of woody browse available to and used by moose. Overall, moose browsed scouler willow, Kenai birch, and aspen to their availability, and avoided black cottonwood. Plant secondary compounds offer a likely explanation for moose avoiding cottonwood and not consuming white spruce (Picea glauca). Percent use of browse species, however, was not significantly related to its availability or to those measures of nutrient content we analyzed. Black cottonwood was not browsed to a greater degree in stand with low resource availability, contrary to a prediction of optimal foraging theory. Patterns of diet selection did not vary between periods of winter even though abundance of forage did so. Distance from escape cover affected diet selection by moose; selectivity of diet declined with increasing distance from cover, indicating risk of predation played a role in the foraging dynamics of moose. The use of fire holds the potential to improve habitat for moose, but the population dynamics of this large herbivore also need to be considered for such management to be effective. Likewise, the sound management of moose requires that suitable habitat be available in other seasons as well as winter.