Response of captive snowshoe hares to thiram-treated conifers

The retention time required for snowshoe hares (Lepus americanus) to maintain a feeding aversion to thiram has important forestry management implications. Thus, we investigated the forage preferences of captive hares for thiram-treated and untreated white spruce (Picea glauca) with animals having either previous exposure or no exposure to treated twigs. Thiram reduced the mean consumption of spruce twigs by previously exposed and naive hares 9-fold and 5-fold, respectively. Previously exposed hares had an untreated spruce intake 2-fold that of naive hares. The decreased consumption of untreated twigs by naive hares in comparison to previously exposed hares suggested that naive animals had developed a generalized aversion to spruce twigs or that previously exposed hares were more adept at differentiating treatment types. The consumption of similar amounts of white spruce treated with thiram by both types of experience groups indicated that a learned food aversion had not been established with previously exposed animals or that extinction of the aversion had occurred. In the wild, even if hares acquired an aversion for treated conifers during autumn through spring, extinction of the aversion would likely occur over the summer months. Consequently, this would not only necessitate the reapplication of thiram more frequently than feasible for foresters, but would also require a reconditioning period for hares during which conifers would be susceptible to browsing damage.