Sunday, September 4, 2011

The Showtl's Underworld, Part 4



Can you see the bristles on its hind feet?

Well, neither can I.

Bristled feet are a diagnostic characteristic of the world's smallest diving mammal -- the American water shrew.

The photo doesn't do justice to the shrew's hairy feet, but that doesn't mean it isn't Sorex palustris. 

It matches the other external features.

Water shrews look like miniature torpedoes when they dive for amphibians, fish and aquatic insects in fast-flowing streams, and they do it all while dog paddling and twirling their tails like propellers.

Shrews (and especially shrews of the red-toothed tribe or Soricinae) live in the fast lane, pushing the envelope of energetic possibility.

They have relatively high thermal conductance, which means they are not well insulated, but their compensation for this deficiency is a high basal metabolic rate (BMR) and high body temperature (38.6 degrees C = 101.3 F).

Thus, shrews are fascinating topics of investigation, but as subjects of energetic study they are frustrating in the extreme.

Within the physiologist's metabolic chamber or respirometer, research subjects are supposed to rest peacefully in a state of post prandial quietude as the equipment measures their oxygen consumption and carbon dioxide production.

And they should also be "postabsorptive" -- not digesting food -- because digestion has a caloric cost and raises metabolism.

Shrews are not good at this, because they are fussbudgets around the clock and they rest only briefly.

Their basal metabolic rate is so high, that the time it takes for food to pass through the digestive system ('throughput" to physiologists, "poop time" to most readers) is about an hour.

Count yourself blessed if you ever see a water shrew.

You have seen a rare sight -- the world's smallest diver, and one of the faster poopers in the west.

Question: the practitioners of what outdoor recreation have the best chance of seeing water shrews?

Post you answer in the comment section, and speak up if you yourself have seen one in action.


References

Gusztak, R.W. , R.A. MacArthur, and K.L. Campbell. 2005. Bioenergetics and thermal physiology of American water shrews (Sorex palustris). Journal of Comparative Physiology, 175:87-95.
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17 comments:

  1. Hugh GriffithSeptember 4, 2011 at 8:10 PM

    What a great trap. Very cool. Those showtls live in busy, busy places. Hypothesis: Dankness is a key factor in mammalian evolution.

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  2. Camera Trap CodgerSeptember 4, 2011 at 9:08 PM

    Hi Hugh, you've got showtls up there too, and I have the feeling they're buddies with Dicamptodon. Keep an eye out.

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  3. AnonymousSeptember 5, 2011 at 12:56 AM

    panning for gold?

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  4. Shervin Hess et alSeptember 5, 2011 at 6:51 AM

    Cavers? (or spelunkers, as they don't like to be called?)

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  5. Camera Trap CodgerSeptember 5, 2011 at 7:13 AM

    Keep guessing.

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  6. randomtruthSeptember 5, 2011 at 9:33 AM

    Shrewo-caching, of course.

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  7. JKSeptember 5, 2011 at 1:14 PM

    Crawfish trapping. Maybe water shrews get stuck in crayfish traps?

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  8. Camera Trap CodgerSeptember 5, 2011 at 1:21 PM

    Keep going, you're getting warm.

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  9. KMHSeptember 5, 2011 at 1:33 PM

    minnow trapping!

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  10. Shervin Hess et alSeptember 5, 2011 at 1:56 PM

    Noodling?

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  11. johnSeptember 5, 2011 at 2:19 PM

    Years ago, I saw what I thought was a Water Shrew, diving under water at the edge of a lake. It was at about 8000ft in elevation, in the White Mountains of Arizona. Now I'm guessing it must have been something else. Maybe an aquatic vole?. Anyway I'll guess that fly fishermen are the people most likely to spot Water Shrews.

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  12. Camera Trap CodgerSeptember 5, 2011 at 5:00 PM

    John got it! Congratulations Big John!

    Yes -- FLY FISHERMEN IS THE ANSWER!

    Actually, crawdad catchers might also encounter water shrews, but noodlers would be looking in the wrong habitat. As far as I know, no fly fishers have hooked a water shrew while angling, but with the right lure itmight be possible (though you wouldn't want to use a hook.

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  13. JKSeptember 6, 2011 at 8:43 PM

    Was that the first water shrew on campus or had you gotten them before? Which species are we still missing on campus? Besides Wolverine of course?

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  14. Camera Trap CodgerSeptember 7, 2011 at 9:09 AM

    That was the second water shrew we've gotten. The first was camtrapped in an alder thicket infested with aplodontia. Missing species include: coyote, red fox, mtn lion, fisher (may not be present), badger, river otter, porcupine (may be locally extinct), beaver, yellow-bellied marmot, and snowshoe hare -- not to mention a bunch of little guys (about 10 species). There's still work to be done.

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  15. JKSeptember 9, 2011 at 8:10 PM

    Wow. We do have our work cut out for us.

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  16. christianSeptember 12, 2011 at 8:53 PM

    Huh, surprised about the lack of coyote and marmot -- given that we saw one of the latter just up the road from the campus last year.

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  17. Camera Trap CodgerSeptember 29, 2011 at 8:10 AM

    We'll get pics of the marmot next year, and hopefully the coyote too.

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