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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.

Sunday, July 31, 2011

Herman the Ermine was alurkin'

Herman the Ermine after cropping

"Study your photos carefully", is my codgerly counsel to novice camera trappers. "Its easy to miss the little guys."

As I gleefully reviewed Bill's showtl pictures the other day I failed to notice Herman the Ermine lurking in the background.

This afternoon Herman finally caught my eye.

Here's the uncropped photo, taken two and a half minutes before Showtl appears in its burrow.


Herman the Ermine before cropping

It could have been a close shave.

We've gotten three photos of weasels (long- and short-tails) in the North Yuba watershed, and they've all been in Aplodontia colonies.

This got me to wondering.

How does the showtl avoid or fend off fatal encounters with predators that can enter their burrows?

Does it have any anti-predator ploys?

You just don't see earth-blocked burrows in showtl colonies.

They don't have the pocket gopher's compulsive burrow-plugging habit which seems to hold many predators at bay.

In fact, from the number of burrow openings you'd think they had an open-door policy with weasels.

Here's a sketch of the burrow system and openings from Charles Camp's study of Aplodontia in 1916.




The strange reality is that showtl knows how to block burrows, but reserves the measure for its underground leaf and root pantries.

Camp wrote,
"A singular habit has been noticed in connection with the storage of food. In a burrow excavated at Point Reyes the entrances of two of the food storehouses were found plugged with large pellets of earth evidently manufactured by the animal for this purpose. These earthen balls were one to two inches in diameter and very hard and dry, evidently from being handled a good deal. It is curious that the outer burrow entrances are not similarly plugged." 
Here's a hypothesis.

Short sections of water-filled tunnels, a water seal of sorts, may bar weasels from entering the showtls nest cavity.

Camp didn't describe such water seals, but if we examined more burrows we might find that they exist.

The problem is that recreational burrow-diggers are hard to find these days.

But one thing is certain. The weasel that nails a showtl is well fed for several days.

An adult showtl outweighs an adult male long-tailed weasel by a factor of 3 or 4.

Herman the Ermine is 1/16th the size of the rodent, so the windfall of flesh would be much greater.

But do ermines take down showtls?

I suspect so, at least young ones.

An ermine is a fierce little killer, and if it can wrap its jaws around the showtl's throat the struggle would be brief.

Showtl emerged 2.5 minutes after Herman moved through

References

Camp, C.L. 1918. Excavations of burrows of the rodent Aplodontia, with observations on the habits of the animal. University of California Publications in Zoology, 17(18):517-536.

7 comments:

randomtruth said...

Excellent spot, Codge. I wonder - does the ermine visit coincide at all with the timing of the vid that our cohort caught on his Bushie?

Camera Trap Codger said...

I'll have to check -- I wondering that too.

Camera Trap Codger said...

Not the same day, Ken. This weasel came through on July 7. Sean's videos were all shot on the first 2-3 days after we set the cams in June, as I recall.

randomtruth said...

Yep - the dash through vid was on June 19th at 5:46pm. I might have to try another trap around that area. Maybe on that big log that crosses through the alders...

Janet said...

VERY cool!

christian said...

This is in the alder thicket, yeah? Was this the first year at that location with weasel captures?

Camera Trap Codger said...

No, last year I got two shots of a long-tailed weasel in an Aplodontia burrow nearby. The other weasel was a short-tail (ermine) about 3 miles up Rt 49.