Nature Notebook – Beaver Tree Preference

The marsh plant population in Sarett’s Brown Sanctuary is going to change now that a beaver has moved in.

The rising water level will “drown” plants incapable of dealing with the reduced availability of the soil oxygen needed to metabolize their photosynthesized food. Plants with oxygen-gathering adaptations will flourish.

The beaver does not travel far from his watery base to gather food. Trees close to the shore will be felled…but not all of them. Beavers demonstrate a definite preference when choosing trees. They like the faster growing soft-wooded aspens, birches, cottonwoods and willows and avoid hardwoods, such as oak. However, they do like sugar maple. Who wouldn’t?

The stumps of the preferred trees will re-sprout. The beavers leave them alone because they contain high concentrations of protective chemicals that are toxic to beavers. While those “new” trees are growing, the non-preferred trees or other plant species fill in the void left by the downed tree. Thus, the plant population changes.

Apparently, beavers don’t care how big a tree is, although sometimes it appears that they have “given up” on a large one. The current thought is that they just wanted a good snack and weren’t planning for the future.