A hard-to-get tree vole

Arborimus pomo, the Sonoma tree vole

At last the hard-to-get Sonoma tree vole, the secret of the Douglas fir forest, the mainstay of Northern spotted owls was captured in pixels.

I hope you are sitting there in wonderment as you view the seldom-seen rodent at work in its nest 35 feet above ground.

And if you want to fill in the picture conjure the feel of the damp coastal air, the woodsy scent of conifers, and the murmur of the Mad River.

The cams had been in the field for 70 days, but the batteries in this one called it quits on November 20th, only 18 days after we made the set.

But 267 images is still a good haul, so we uploaded to my laptop on the tailgate of Terry's pickup, and as we flipped through the images we found that the vole's nest had a life of its own.

Indeed it expanded and deflated like a slumbering mini poodle, and several shots showed a centipede and a millipede grubbing about in the midden of resin ducts and twigs.

The tree vole on the other hand exposed itself in only 10 pictures, and of those only two were full body shots.

She revealed her tail and slender hips,

A full frame view of the nest of Douglas fir needles with the vole hauling a Douglas fir sprig.

but most of the time she was hauling and hidden behind twigs of Douglas fir.

A cropped view of the vole from the photo above. 

Back home I retrieved my Arborimus file and found that our modest success was a far cry from that of Eric Forsman and his colleagues at Oregon State University who studied the related red tree vole (Arborimus longicaudus).

Using a commercial video camera system they captured and analyzed over 300 days of videos totaling 6700 hours, and refuted the belief that tree voles are "slow, docile and somewhat clumsy climbers".

That dubious reputation was based on observations of sleepy and confused tree voles that had been rousted from their nests during the day.

On the contrary, they found that foraging voles "were often so rapid it was hard to follow them as they scurried in and out of the nest."

That speed explained why over 95% of our pictures were blank; the rodent activated the camera trap's sensor but was usually gone when the shutter released.

As for the changing size of the nest, successive photos show resin ducts accumulating at the top of the nest and then sliding down.

It seems the vole's favorite feeding perch might have been just above the camera's view.

One of these days we'll take on the tree vole with a video camera, but I make no promises as to when.

I have two DXG 125s on the work bench, but hacking an HD video camera is far more intimidating than a point and shoot camera.



Reference

Forsman, E.D., J.K. Swingle, and N.R. Hatch. 2009. Behavior of red tree voles (Arborimus longicaudus) based on continuous video monitoring of nests. Northwest Science, 83(3):262-272.