Severe snowshoe hare (Lepus americanus) browsing causes adult feltleaf willow (Salix alaxensis),in the Alaskan floodplain, to revert to the juvenile form for 2-3 years as a defense mechanism against further browsing. Results showed that snowshoe hares preferred twigs of adult shoots, rather than juveniles, formed after decapitation; chopping of juvenile twigs did not increase palatability. Nutritional quality and energy in juvenile sprouts were equal or higher than in adult form, but contained more ADF (acid-detergent fiber), and had higher concentrations of lignin and condensed tannins. This indicates that avoidance of secondary compounds, rather then selection for nutritional quality, is the driving force behind the varied use of this important winter forage. These results are compatible with the hypothesis that the induction and relaxation of resistance to browsing in feltleaf willow is a cause of the well-known 10-year snowshoe hare cycle.
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