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January 2020 Natural Mystery Answered

posted Feb 11, 2020, 11:07 AM by Jonathan Poppele   [ updated Feb 11, 2020, 11:10 AM ]
Our January Natural Mystery proved smooth sailing for several of our regular contributors. Congratulations to Kim Cabrera, Kathy Dean, Anne Marie Meegan, Kirsten Welge and Brendan White for identifying both the track maker and the track pattern. And thanks to Anne Marie, Kim & Kirsten for sharing their thinking with the rest of us.

These are the tracks of an American Mink. The track pattern is the 2x2 double register typical of small mustelids which some people call a 2x2 lope and others call it a 2x2 bound. Let's start with the identification:

Kirsten starts us off by analyzing the individual tracks:

"Morphology of the hind track (which is clearest in the uppermost right track) shows 5 toes arranged around a triangular or chevron-shaped metatarsal pad. Toe 1 is set further back, with the other 4 toes forming a symmetrical canine-like arrangement. Toes are registering clearly, indicating the bottom of the foot is not heavily furred. Hind track size is about 1 3/4"" long and perhaps 1 1/4"" wide.

The hind track is overlaid on the front track, but we can still make out the front track metacarpal pad and a heel pad (the lowermost dot in the right track set)."

These are all features of mustelid tracks, and identify our track maker as some sort of weasel. Anne Marie notes that the tracks “look too small for Fisher and too big for long or short tail weasel.” But she also noted that we cannot rule out marten based on size alone.

Kim explores explores the difference between Mink and marten in more detail:

"The toes are pretty clear, indicating that the bottoms of the feet are pretty bare. That's more typical of mink than marten. Mink and marten are close in size, sometimes use the same habitats, and both use the 2X2 lope gait. But, these tracks show more details in the snow than I think a marten would."

I'll also note that Keller Regional Park in the Twin Cities is about 150 miles south of the closest marten observations posted on iNaturlaist.

Now about that track pattern.

Kim notes that “The pattern is evident because you can see all four tracks, with the hinds on top of the fronts.” While Kirsten similarly points out that “This picture shows a double register (hind track registering atop the front track) on each side of the body." Yet they named the pattern differently. In fact, the group was evenly divided in what it called this pattern with two people calling it a “2x2 lope,” two calling it a “2x2 bound,” and one fully inclusive person calling it a “2x2 lope or bound.”

So which is it? And does it matter?

There is not yet a consensus in the tracking literature, with both 2x2 lope and 2x2 bound being used—sometimes by the same author. The important considerations for us are if we can recognize this distinctive track pattern of the weasel family and communicate to our fellow trackers. And it seems we are able to do that, despite the uncooperative terminology.