Does nursery production reduce antiherbivore defences of white spruce? Evidence from feeding experiments with snowshoe hares

Abstract

Previous studies indicate that snowshoe hares (Lepusamericanus Erxleben) readily browse nursery-grown white spruce (Piceaglauca (Moench) Voss) seedlings but tend to avoid naturally regenerating juvenile trees. We confirmed these observations in feeding trials with snowshoe hares and investigated several possible explanations for this phenomenon. In vitro digestibilities of nursery-grown and naturally regenerating white spruce seedlings were similar, indicating similar contents of acid detergent fibre. Thus, it is unlikely that snowshoe hares are better able to extract nutrients from nursery-grown seedlings than from naturally regenerating white spruce. We suggest that snowshoe hares prefer to feed on nursery-grown seedlings because they contain less camphor (a specific compound in white spruce shown to deter feeding by hares) and have higher nutritional value (i.e., nitrogen) than naturally regenerating plants.