College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA.
Last year at Ithaca we presented preliminary data on the question whether beavers soak some of their food branches in water in order to leach out undesirable compounds. New experiments of three types expanded this study. 1) Experimental logs of 3 tree species (trembling aspen, Populus tremuloides, red maple, Acer rubrum, and witch hazel, Hamamelis virginiana) were provided on land or in the water to 6 beaver colonies; 2) branches (N=636) with leaves of 15 tree species were placed in the water at 8 colonies; and 3) branches harvested by the beavers themselves were monitored over 7 days for retention time in the water at 7 colonies. The time periods for which logs or branches were left in the water before being consumed fell in two patterns. Most tree species were eaten most on the first day, and in diminishing amounts one and two days later. Some species, notably witch hazel and red maple, were initially avoided and eaten more after they had been in the water for 2 or 3 days. This is consistent with the notion of leaching. Red maple and witch hazel contain high levels of phenolics. We tentatively conclude that some tree species under certain conditions, such as what other foods are available to the animals, are more attractive to beavers after several days of soaking in water.