Arb Notes for February 24 - Beavers

February 22, 2011
By Callie Millington '12


A lot of people hate beavers.

Whether the beaver families in the lower arb know that or not, they don’t seem to care. (They’re busy passing the winter socializing in their lodges, if you recall an earlier Arb Notes…)

Beavers have earned a bad rap for their tendency to chew down our favorite trees and flood our fields. In fact, over the past century beavers have been actively hunted and trapped out of much of the United States, countless dams have been dynamited, and communities have been divided by beaver-related conflict. Even today a few misplaced words about beavers to a rancher in Utah could land you in an unpleasant situation. Carleton itself has had trouble with beavers in Lyman Lakes (a good story to look into if you’re looking for procrastination). Who knew such a friendly, furry creature could be so contentious! So are these beavers really as bad as we think? Or are they simply misunderstood?

It’s true that beavers can alter a forested area quite quickly. They fell trees, mostly aspen, cottonwood and willow, for food and building material, and sometimes the fallout has the looks of a massacre. Their complex series of dams can also completely change streams and rivers. Because beavers are vulnerable to predation on land, they use dams to create systems of still water ponds that provide safe access to their food source. Unfortunately, these dams often flood farm fields and create marshes where a landowner might not want a marsh.

In spite of their reputation for destruction, beavers provide many vital services for an ecosystem. Beaver ponds serve as “road bumps” that slow water down. Especially after storms or during spring run-off (recall those brief, soggy days of last week) this can mitigate erosion. In addition, beaver dams prevent mass loss of topsoil by trapping sediment that would otherwise ride the river straight downstream. Because beaver dams turn flowing water into standing water, they also allow for better aquifer recharge. Especially in arid regions of the U.S., beaver dams ensure our drinking water supply. 

So even though they might seem like a threat to an ecosystem, beavers are actually good for watershed health! Check it out for yourself—the Arb is home to multiple beaver families. Take a walk to the retention pond or along the river and look for beaver sign. Freshly-gnawed stumps, recently felled trees and saplings, woodchips, and piles of logs with tell-tale conical ends are all signs that a beaver has been around. And if you run into a real live beaver, for goodness’ sake be nice (and don’t take out your rifle)—they’ve been ostracized enough as it is.

  -Callie Millington '12, for the Cole Student Naturalists