Food processing by animals: Do beavers leach tree bark to improve palatability?

Beavers store and consume tree parts in the bodies of water where they live . We examined whether such soaking renders food more palatable by leaching out undesirable compounds. In experiment I, saplings of red maple, Acer rub rum (RM), were first soaked in a pond for periods of 2, 18, and 36 days, th en offered to free-ranging beavers. Soaking for two days rendered RM slight ly more acceptable to beavers. To further examine the time window around tw o days, RM sticks were soaked in distilled water in the laboratory for 1, 2 , 4, and 6 days before presenting them to beavers (experiment 2). In experi ment 3, twigs of three species were placed on land. Beavers placed RM in th e water for 1 to 3 days before consuming the twigs. In experiment 4, sticks were provided in the water at Cranberry Lake Biological Station (CLBS). Mo st quaking aspen (QA) was consumed during the first night, and most witch h azel, Hamamelis virginiana (WH), during the third night. At Allegany State Park (ASP), no such difference was found. Twigs were provided in the water in experiment 5. At ASP, WH was taken after three days in the water, and at CLBS little WH was consumed, and only during the third night. A meta-analy sis of all experiments shows that relatively more WH is consumed after two days than any other species. Experiment 6 traced the time beavers left thei r own harvested branches in the water. Unlike other tree species, WH remain ed in the water for two to four days before being consumed. Experiment 7 me asured the phenolics leached into water from RM twigs and small pieces of b ark soaked for 10 and 8 days, respectively. Shredded bark lost 50-60% of le achable phenolics into the water, and twigs 70-80%. We conclude that beaver s can use water to leach undesirable compounds from their food. Although th is effect was not robust, our study is the first of its kind.