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January 2021 Natural Mystery Answered

posted Feb 17, 2021, 9:15 AM by Jonathan Poppele   [ updated Feb 17, 2021, 9:16 AM ]
It looks like people had some fun with last month’s natural mystery. At a quick glance, it resembles a cat or dog track—but Bill Cass, Kirsten Welge, and Rob Grunewald saw through this first impression and correctly identified the track maker. They even took a stab at narrowing it down to the species.

These are the tracks of a typical squirrel—a member of the Tribe Sciurini, which includes the red squirrels, gray squirrels and flying squirrels.

Bill starts us off with these observations:

“Although from a distance it could be mistaken for a cat track, we see individual toes in the ‘toes’, so instead of toes we have four individual feet, meaning the ‘heel pad’ is actually a butt. Although the toes are not clear, they are long, clawed, and arranged symmetrically.”

Rob adds that “toes 2, 3, and 4 in the two outside hind tracks are close together, indicative of a squirrel track.”

So these are squirrel tracks. Can we narrow it down to the species? Rob suggests that with the observation coming from just outside Buffalo “the habitat would lean more toward a gray squirrel than a red squirrel.” That’s a reasonable place to start, but there is reason to be cautious here. I get red squirrels in my urban back yard in St. Paul. Similarly, a search on iNaturalist shows a number of observations of red squirrels in the Buffalo metro area. Gray squirrels are unquestionably more common, but it doesn’t look like we can rule out red squirrel based on what we know about the location.

Kirsten offers some additional details about the tracks to make a good case for a Sciurus species while also using my new favorite vocabulary word:

“The right impression also shows a clear, robust trapezoidal metapodial pad, which is diagnostic for one of the larger tree squirrels. The size of negative space between the toe pads and metapodial pad also points to a larger tree squirrel. A red squirrel would show more delicate toe pads, and a longer negative space between metapodial pad and toe pads.“

The details of the foot morphology do indeed point us toward a large tree squirrel in the genus Sciurus. The two large tree squirrels in the eastern US are the Fox Squirrel and Gray Squirrel. Mark Elbroch notes that “the hind toes of fox squirrels are slightly more compact than those of gray squirrels,” but also that “the tracks and trails of these species are similar and easily confused.” So let’s consider the range of each species.

Many range maps suggest that fox squirrels could be found in the Buffalo, NY, area. But the reality appears to be that they are exceptionally rare near by. A search on iNaturalist shows only 3 fox squirrel observations within 50 miles of Buffalo, only one of which is Research Grade. This leaves the eastern gray squirrel, Sciurus carolinensis, as our most likely candidate.

Congratulations again to Bill, Kirsten and Rob for sharing their answers and their reasoning with