Basey et al. collected data on the availability, size, bark chemistry, and extent of cutting by beavers (Castor canadensis) of quaking aspen (Populus tremuloides) at two sites, one occupied for 28 years and the other only recently occupied by beaver. Much more aspen was utilized in the longer occupied site compared to the recent site (23% vs. 3.8%, respectively). On the longer occupied site, 49% of trees exhibited juvenile growth form (which has higher concentrations of a phenolic compound that may be a feeding deterrent for beavers), compared with 14% at the newly occupied site. Beavers at both sites showed a highly significant selection of trees based on diameter class and distance from the pond, although they selected against trees with diameter less than 4.5 cm in the longer occupied site. The two foraging models, minimizing secondary compounds and maximizing net energy gains, were both supported by this study. Beavers selected smaller diameter trees at larger distances on the recently occupied pond, but avoided them when secondary compounds became elevated, such as in the longer occupied pond.
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