 They are as easy prey for wolves and they create aquatic macrophytes, very nutritional plants for moose, although the macrophytes are also consumed by the beavers.Though wolves are thought to contribute to the decline in beaver, researchers believe that the decline of aspen, the primary food source of beavers, which used to be plentiful, could have led to their decrease.Beavers have been exposed to predation by having to travel long distances to find only parts of the island where aspen remains.