One Month in Subterranea

This little movie is part of a continuing saga, a self-inflicted exercise in hope and frustration that started 4 summers ago when we found a collapsed mountain beaver tunnel in the northern Sierra Nevada.

In a strange way that narrow collapsed section of the tunnel resembled the shotgun-blasted stomach of Alexis St. Martin, the trapper whose misfortune set the stage for William Beaumont to become the grand old man of gastric physiology.

Like the gaping hole in St Martin's stomach, this mountain beaver's tunnel had a portal that exposed the mysteries within.

Collapsed mountain beaver burrows however are a dime a dozen.

What made this one special was that it opened up into an underground cavity big enough to accommodate a camera trap without blocking the passage.

Plus, this was not one of those thin-roofed sub-surface tunnels. This one was nearly 2 feet deep, making other cave-ins unlikely.

We started in 2010 by setting a still camera down there, a Sony s600 to be exact, and though there were lots of blank exposures the animal images were thrilling to see.

We learned that the mountain beaver's burrow system is a commons used by a lot of seldom-seen freeloaders like weasels, mink, and water shrews, not to mention great swarms of mosquitos.

Two summer's passed before I asked, "Why not video?"

It was an iffy idea, but I thought a few clips of the subway traffic would satisfy my whim and allow me to move on to other projects.

So I bought a home brewed DXG 567 from a fellow camtrapper and set it out in June, 2011 for the forthcoming workshop.

A bear cub unearthed the cam a couple weeks into the bargain, but not before the camera sampled some of the underground fauna.

In 2012 we tried again and discovered that chickarees actually mine the tunnels for truffles.

Now I was really hooked, even though the quality of the video schtunk.

The lens's field of view was too narrow, and depth of field was crumby.

So last winter I replaced the old lens with a $20 4mm wide angle lens from EBay.

The results are what you see above.

I am pleased with improved field of view, disgruntled with the focus, and flustrated with all the false exposures.

The camera is just too slow, and fixing it will be this winter's project.

My plan is to go back to the site and find all the entrances leading to that treasured tunnel.

If I can set external PIR sensors in the burrow entrances the camera will be rolling when the critters come cruising down the tunnel.

Will the real Ermine please stand up

September 3, 4:39AM -- in the showtl's underworld

We are just back from the north fork of the Yuba River.

Yesterday, the Codger, the Redhead, Audrey, and Fred pulled the last three camera traps, and I am terribly amped.

The picture above is one of the reasons.

You may recall that the codger was uncertain that "Herman the Ermine" was correctly identified in a recent "underworld post".

A few commentors thought the suspect was an American mink.

The unmistakable ermine pictured above confirms that the previous mustelid was indeed Slinky the Minkie.

This ermine was photographed in the same Aplodontia (=showtl) tunnel where the mink made its appearance last month.

To get an idea of the relative sizes of this little predator and its prey, compare the two pictures, which I have cropped more or less to the same size.

Like the mink, the ermine evidently failed to find the showtl, which showed up 6 days later.

Its absence makes you wonder if predator detection changed the rodent's use of the tunnel system.

Anyway, we're not done yet.

We staked out several Aplodontia burrows for camera trapping next year.

Our winter work is cut out for us. We've got to get faster cameras so we can diminish the number of false exposures down there in the showtl's underworld.

There's a lot of traffic and probably a few visitors that are just too fast for our cameras.

And to give you a bigger view of the showtl's busy underworld, here's an uncropped photo.