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

Wednesday, December 19, 2012

Canned shrew

Winter is a good time to find canned and bottled shrews.

Many walkers around here deem their daily communion with nature incomplete without the comfort of a brewski or two, and tossing the cans or bottles in the brush is apparently de rigeur.

Shrews are attracted to the containers at any time of year, but codgers can find them more easily in winter and redeem them for cash.

Nonetheless, it's been a coon's age since I've found a canned or bottled shrew.

So when I saw that can of Mickey's Malt Liquor tilted upward in the duff I went for it.

It had several ounces left in it, and I could tell there was something soggy in there too.

Sure enough, it was another Trowbridge shrew (Sorex trowbridgeii).

It was the right size and color, and the tail was bicolored, but in winter the wandering shrew (Sorex vagrans) looks quite similar.

The definitive identification had to wait until I could look at its 4 unicuspid teeth.

The photo doesn't do justice to the structure of the teeth, but it gives an idea of what you see under the dissecting scope.

Just keeping the wet shrew on the microscope stage while lifting the upper lip is a frustrating exercise, but that's what it takes to see the 4 diagnostic unicuspid teeth. Their relative size differs between species. The pigmented upper incisor is also slightly grooved.

Trowbridge and wandering shrews are the two common species I've found here.

Empty beer cans and bottles are not encyclopedias, but looking into them is a good way to learn about your local shrews.

Redeem them at your local recycling center, and you can actually get paid to learn about charismatic micro-mammals.

Monday, December 17, 2012

From homely juvenile to young prince

Bushy-tailed wood rats aren't born beauties. 

In youth they look like any other rat, especially with that ratty tail and brownish-gray coat.

A few months later however, their tails gets hairy and their coats acquire buffy highlights.

This animal of the subspecies Neotoma cinerea pulla was camera trapped last summer in a talus slide in the central Sierra Nevada, and I suspect it is a young adult.

In one night we got 54 photos of several woodrats, and there were three age classes.

Unfortunately, a large bulky rat, presumably a male, was the most timid subject, and all images of it were partial pictures.

The subspecies occidentalis seen in the previous post is more silvery and regal in coloration than these woodrats of the Sierra Nevada.

They are all good-lookers though.

Wednesday, December 12, 2012

A dirty filthy but princely rat

A bushy-tailed pack rat (Neotoma cinerea) in a pile of slabs in an abandoned saw mill (Flathead County, Montana).

They may be the best looking rats in North America, but it doesn't matter. In western Montana bushy-tailed wood rats are regarded as dirty filthy rats.

"How could such a princely rodent alienate so many?" I ask.

"Because they stink, they make a mess, and they crap and piss all over the place", Carl answers.

Carl's photos show the ugly truth happening on his front porch.

Bushy-tail caught during intimate moment
 of fecal assessment. (Photo by Carl Hansen)

A poop-obsessed pack rat seems to nuzzle and whisper tenderly to its fecal pellet.

Bushy-tail aids in the delivery of a fecal pellet
(photo by Carl Hansen)
And here you see the rat aiding the passage of a fecal pellet with the tender care of a midwife delivering a babe.

This may be an example of coprophagy -- recycling nutrients in the fermentation products of the caecum, but never mind.

Even David Attenborough's soothing zoological wonderment at such phenomena would not change the minds of the pack rat's detractors.

A pack rat midden in an abandoned cabin.
The beautiful furry rat has other unsavory habits -- like moving into human habitations and decorating with foliage, twigs, and anything else that strikes its fancy.

The middens become their toilets, glued together with urine and feces, and in due course the reeking mass solidifies, crystallizes, and becomes amberat, which acquires a resinous bouquet, and in fact was once mistaken for Native American peanut brittle by a gang of starving 49ers.

The pack rat however has redeeming qualities beyond its good looks and silky Chinchilla coat.

Scientists now know that this dirty filthy rat is an environmental historian.

Countless generations of pack rats have been contributing to some middens for at least the past 25,000 years.

These paleo-middens are monumental edifices hidden in rocky canyons and caves, and they contain a treasure trove on data on environmental change and its consequences on body size as an adaptation to heat dissipation.

The biologists quickly realized that fecal pellets in paleo-middens were not all the same size, and used Carbon 14 dating to assign ages to feces and associated plant parts.

They validated the relationship between pellet size and body size by examining several species of wood rats, and they did other tests to verify their findings.

Guess what?  Pack rats that lived 20,000 years ago in the shadows of the glaciers were impressive hulks.  They are estimated to have weighed as much as 450 grams (roughly a pound).

They grew smaller as temperatures increased after the last glacial, and by the mid-Holocene, about 6000 years ago they were 20% smaller than their ancestors.

It paid to be big, and even today the bushy-tailed wood rat is the largest living species of its clan.

The old pack rat may have a few nasty habits, but it's still a princely looking rodent.   

"Where is it? The viagra doesn't seem to be working".


Smith, F.A., J.L. Betancourt, and J.H. Brown. 1995. Evolution of body size in the woodrat over the past 25,000 years of climate change. Science, Vol. 270:2012-2014. 

Sunday, December 2, 2012

The secret cache

The secret cache, now stashed in a
chainsaw chain container. 

For the sake of the story, I'd like to say . . . "when Carl reached the rafters and tugged the black plastic bag, the truffles showered down with the force of a Montana hailstorm".

But it wasn't exactly so.

The garbage bag contained truffles alright, but they were tucked into the folds of two canvass cots intended for the codger and the redhead, who were about to arrive from California.

For the sake of the story I might also add that "Though we slept comfortably in our sleeping bags, those cots infused our slumber with a subtle but pleasing essence of shaved tartufi stewing in risotto."

But it wasn't exactly so. The truffles give off a mild odor, but the cabin smelled of lodgepole pine logs and fried steak.

Looks like several species.

I am tempted to say that "the delectable fungi were evidently the last will and testament of 'Old One-eye', the murderous Montana chickaree whose squirrelly chutzpah summoned his own demise.

But I'm not sure the sack of dried truffles was actually of his doing.

The chickaree isn't the only mycophagist  in our western forests. There is no shortage of truffle gourmets, including several species of chipmunks and the northern flying squirrel.

Biologists used to examine stomach contents to learn about food habits, but now they can identify truffle eaters by the spores in fecal pellets.

It's tedious work, but Carl could identify the maker of the secret cache with much less effort.

All he has to do is stuff a camera trap inside a black plastic bag with two canvass cots and hang it in the rafters of the shed.

If he's too busy I know an old codger who would be more than willing to give it a try.