A well-known fact about beaver lodges, one that any close observer has surely noticed, is that they’re often home to muskrats. I’ve seen this many times, never more than last week up Clear Creek here in central Colorado, where three or four busy muskrats seemed to constantly be motoring to and from a lodge, gathering their bundles of grass with the utmost purpose and industry, their little tails churning the surface like propellors. (By the way, note to everyone who emails me to report alleged beaver kit sightings: If you can see tail movement, you’re watching a muskrat. Beavers swim with their hind feet.)
This frequent cohabitation leaves me with two questions. First, why do the beavers tolerate these semiaquatic freeloaders? Maybe the relationship is simply one of commensalism, whereby the muskrats benefit (in the form of a home, obviously) and the beavers are unaffected. (It’s not like a muskrat takes up much space.) Or perhaps there’s some mutualism at play. A couple days of camera-trapping and direct observation at Clear Creek revealed that the muskrats emerged fairly early each evening, well before dark, whereas the beavers didn’t become truly active until night had nearly fallen. Are the muskrats somehow acting as sentries or scouts, confirming the coast is clear for their more cautious rodent roommates?
Second question: where do they all sleep? Do the muskrats excavate their own miniature chambers? I’d prefer to imagine the two colonies, beavers and muskrats both, nuzzled together in a single capacious cavity, a big furry pile of hot soft bodies snuggling and snoring through the chill Rocky Mountain winters. You’re welcome for that adorable image.
Anyway, lest you think I only detected muskrats, here’s a spot of late-night maintenance performed by one of the lodge’s true architects, benevolently building for the benefit of other species, as per usual.