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Native Californian, biologist, wildlife conservation consultant, retired Smithsonian scientist, father of two daughters, grandfather of 4 small primates. INTJ. Believes nature is infinitely more interesting than shopping malls. Born 100 years too late.

Thursday, July 10, 2014

Errant Mountain Beaver

Folks up here on the ridge were recently roused to declare their biophilia when a mountain beaver was reported swimming down the Butte Creek Flume.

One of our local naturalists, a retired bike-riding school teacher known by his avatar Forest, documented the rare event in video.

This is the first verified record of mountain beaver in Butte County, and the discovery begs the question: From whence the errant rodent?

I'm an enthusiast of these guinea pig size rodents, and I recognize their haunts when I see them, but I have never seen their signs in the county of Butte.

They require lush vegetation for food and live in moist habitats with shallow water tables, Their burrows often tap into underground springs.

I guess I have to look a little harder.

Arctos, an extensive database of zoological records, lists mountain beaver specimens from several counties in the Sierra Nevada, including Shasta, Plumas, Eldorado, Sierra, Nevada, Placer, Mono, Mariposa, and Tulare.

I suspect this particular rodent entered the flume voluntarily, swam around, and went with the flow.

But here's the rub. Its flume float could not have been longer than about 3 miles.

If the rodent had embarked on its swim further upstream it would have passed into a deadly siphon that conveys the water down and then up a ravine.

Even Houdini couldn't have made it through that siphon alive.

If the mountain beaver's odyssey started above the siphon, it had to travel by land to bypass the siphon and reach the flume's navigable portion.

Unfortunately, the neighborhood's flumes do not lead to suitable habitat for mountain beavers. So I doubt this rodent's trip led it to greener pastures.

It was an unusual event and it makes you wonder.

Did the mountain beaver abandon its home because of the drought? Or was it just a normal attempt to disperse that few people ever see?

We're lucky to have naturalists like Forest here.


Dale said...


A mountain beaver for sure. Likely a dispersing young animal. Although they aren't known to move any great distance, there have been a number of observations made of them showing up in strange places and considerable distance from any known habitat. Especially at this time of year.

I don't know the elevation at this site but used to consider around 5000' elevation a crude cutoff for occupied mt. beaver habitat.

Based on limited long term records in a few places like Sequoia NP it seems that small sierrian mt beaver populations may wink out and later reestablish this way. I think the same is true for the east slope of the sierras based on personal observation.

A mt beaver" body surfing" down an active flume might be a first but I suspect it's been done before but never captured as with this great footage!

Well done.


John W. Wall said...

It looked like there was a mess of salmon in one of those pools, and the beaver's passing didn't spook them.

Camera Trap Codger said...

John, no salmon, but a few trout.

Thanks for the note, Dale. Greg sent me info on the exact location, and I'll do a little exploration there soon.

Anonymous said...

Great find and video by the "retired teacher" and of course the Codger is now on it like flies to dead meat!
I hope you figure the mystery out Sherlock and by all means you will keep us posted.