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Last month's Natural Mystery was a set of tiny tracks found by a participant during the October 14-15 Track & Sign evaluation. They were no more than an hour or two old when the photo was taken. Congratulations to Kirsten Welge, who correctly identified the diminutive track maker. For the answer to the mystery, I'm going to turn things over to Kirsten to walk us through her process.
These are the tracks of a small shrew, most likely a Masked Shrew (Sorex cinereus). Here are Kirsten's notes, detailing her ID process:
"Observations:
Four tiny tracks are visible, in a compact bound.
Tracks show longer, delicate, more fingery toe and metapodial pads.
Right hind shows 5 toes, and measure 6 mm L x 6 mm W. Middle three toe tips are in an arc, rather than straight across.
Right front also shows 5 toes, and measure 4 mm L x 5 mm W.
Trail width measures 2.2 cm (3/4"); bound group measures 1 cm (3/8").
"Interpretation:
Initial candidates included shrew, vole, and mouse.
Trail width under 1" is consistent with shrew, and under the range for vole and mouse.
Bound group of 3/8" is under the stated range for all candidates; shrew range is closest at 1/2"-2".
Track measurements are below stated size limits for mouse and vole, but consistent with shrew.
"Measurements are consistent with the smallest of our local shrews, Sorex cinereus (Masked Shrew)."
Exactly right. I would only note that there are a few other less common species of long-tailed shrews that we might consider. The Twin Cities Metro Area is inside the range for the American Pygmy Shrew (Sorex hoyi), the Arctic Shrew (Sorex arcticus), and the Northern Water Shrew (Sorex palustris). We are a bit outside the published range for the North American Least Shrew (Cryptotis parvus), but close enough that I wouldn't completely rule it out. What we can say with confidence is that these are the tracks of a small shrew, most likely a Masked Shrew, and almost certainly a long-tailed shrew in the genus Sorex.
Congratulations again to Kirsten for her correct, and well detailed answer. Thanks as always to everyone who submitted an answer, as well as all of you who read these Natural Mysteries and Natural Mystery Answers.
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