May 2023 Natural Mystery Answered

Last month’s Natural Mystery showed the tracks of a species we have rarely identified in Ft. Snelling State Park. The only other time I have confirmed tracks of this species in the park was under this same bridge on a CyberTracker evaluation with Nate Harvey. Every one of us taking the evaluation got the question wrong. This time around, Kirsten Welge sorted out the mystery and successfully identified who left these diminutive footprints.

These are the tracks of a weasel, most likely an ermine (Mustela richardsonii), also known as the short-tailed weasel.

Kirsten’s answer is thorough, detailed, and walks us through her process. I’ll turn it over to her to explain how she sorted out this mystery:


Four small compressions are present, showing distinct bulbous impressions. Overall track shape is roughly round and even-sided. I measure the track below the 1 cm mark at 1.3 cm x 1.4 cm. There is no notable difference in size.


Looking closer at these tracks:

When no candidates fit the track, it's time to re-examine my candidate pool. Who *does* have:

Looking further afield for candidates:

Frog/toad? I briefly considered frog/toad due to front turn-in, but ruled out immediately due to hind toe morphology & foot placement.

Rabbit? I can't match their symmetric four toed hinds or highly irregular five-toed front tracks to any of these options. Also, this track set is a mess compared to the neat bounds I expect from local leporids. I'd be shocked if this was a cottontail.

Mole? There's not enough claw or inward curvature from the front tracks.

Mustela species (least weasel or short-tailed weasel)?

I'm calling this short-tailed weasel."

Exactly right. I like Kirsten’s thorough process of elimination here, and her willingness to cast a wider net when her observations weren’t matching her initial candidates. Sometimes we misidentify tracks simply because we never consider the right candidate. Congratulations again to Kirsten for sorting out this challenging mystery.

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