Posted by: salamandercandy | February 6, 2007

Hooray for Beavers!

Now I have a reason to approve of Oregon State University’s alarmingly angry mascot, Benny the beaver. It turns out that beavers, by virtue of their proclivity for dam-building, help out amphibians by creating pond habitats where there had been none. Beavers gnaw through trees and pile the felled logs to build dams across streams. Though this behavior seems destructive (and I guess it is from the perspective of an individual tree), it has long term benefits for the whole forest ecosystem. Beaver ponds eventually turn into wetlands after the beavers split and the dam breaches. The wetlands are incredibly valuable bits of natural real estate because they are home to many organisms (including amphibians!) and are important for nutrient cycling. Eventually, the wetlands dry up and become meadows, which are invaded by trees, and then the beavers can move back in. The circle of life.

A recent study published in Biological Conservation found that beaver-created ponds can serve as breeding habitat for several anuran species in Canada. These species totally hate streams, but ponds please them down to their very souls. Okay, so I am being stupid—the point is, more ponds equals more frogs. The beavers win, the frogs win, people who don’t despise nature win.

From the abstract:

We propose that the distribution and abundance of beaver ponds could be determined over large areas quickly and inexpensively by remote sensing and used to identify and monitor amphibian habitat, and possibly, populations. This work establishes the pre-eminence of beaver-created wetlands as amphibian habitat in the Boreal Foothills and that the incorporation of dam-building patterns into forest management strategies could aid amphibian conservation.

This makes me wonder… The Oregon spotted frog (Rana pretiosa)—a species that we study in our lab and that has been extirpated from the Willamette Valley where it was once common—might have benefited historically from beaver activities. If beaver populations were greatly reduced by trapping, maybe there was an associated loss of pond habitat which was one reason the frogs died out? This is pure speculation, because I don’t know what the state of beaver populations is in the valley and I don’t know if they ever coexisted with Oregon spotted frogs. Just a thought…


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