Beavers are herbivores. Beavers appear to prefer herbaceous vegetation over woody vegetation during all seasons if it is available. Woody vegetation may be consumed during any season, although its highest utilization occurs from late fall through early spring when herbaceous vegetation is not available. Winter is a critical period, especially for colonies on streams because they must subsist solely on their winter food caches. One study reported that trees of all size classes were felled close to the water's edge, while only smaller diameter trees were felled farther from the shore.
Beavers have few natural predators.
However, railways, roads, and land clearing adjacent to waterways may affect beaver habitat suitablity. Transplants of beaver may be successful on strip mined land or in new impoundments where water conditions are relatively stable. Through tree harvesting activity, beavers can have an effect on natural succession. Beaver activity can also improve fish habitat. In areas of marginal trout habitat, however, beaver activity can reduce trout production.