December 2024 Natural Mystery Answered

We received a number of highly detailed answers to last month’s Natural Mystery. It seems that many of you are deeply familiar with this critter’s tracks. Congratulations to Ronnie Hartman, Robert Daun, Collin Arnett, Maria Wesserle, and Erin Anderson for correctly identifying the track maker to species and correctly identifying which foot made this print.

This is the right hind track of an eastern gray squirrel (Sciurus carolinensis)

We’ll start off with Ronnie’s description of the track:

“I see five toes, with toe 2, 3 and 4 roughly parallel to each other and well ahead of toes 1 and 5. I see significant negative space between the toe prints and the metacarpal pad, and I see sharp nails at the tips of the toes. Toes 1 and 5 are both set back and well to the sides.”

Robert points out that “the flatness of the three middle digits differentiate it from the ‘candle flame’ shape of a rabbit track.” Erin and Maria note that “the 1-3-1 toe arrangement is typical for rodents.” and specifically “indicates that this is the track of a hind foot.”

To determine which side of the body, we can look at the spacing between the toes. Maria explains it this way:

“The spacing between toe 1 and toe 2 is the largest between the toes (akin to our thumb and forefinger on our hands.) Therefore, we can tell that toe 1 is on the left side of the photo, making the foot a right hind. The remaining spacing between toes, from largest to smallest, is as follows: toe 4 - toe 5; toe 2 - toe 3; toe 3 - toe 4. We can also see this arrangement reflected in the photo above, proving this to be a right hind.”

To identify the species, we can begin by looking at size. Erin, Collin and Ronnie all measured this track as 1¼” long. But Maria points out that the heel does not show in this track, and that published track sizes for rodent hinds often include the heel. Rather than just comparing numbers, she suggests comparing the track to good quality life-sized track illustrations. When we do this, we find that not only is the track considerably larger than those of brown rat, chipmunk and smaller ground squirrels, but also considerably larger than the tracks of flying squirrels—even though Glaucomys hind prints can measure up to 1½” long. Similarly, although the measurements of this track fall within the published range for red squirrels, comparing to life-sized illustrations helps us see that this would be, as Robert notes, “an exceptionally large red squirrel.”

Erin then looks at the track morphology to further rule out red squirrel:

“I see notable negative space between the toes and the palm pad, which is uncharacteristic for red squirrels, whose toes often connect to the palm in the track. They also have delicate, elongated, and fingery toes, and I don't see those characteristics here. These toes look a bit more stout and bulbous and do not seem to connect with the palm pad.”

Maria explains how we can rule out ground squirrels, including woodchuck:

“We might also consider ground squirrels, but we know that this photo was taken in a Saint Paul neighborhood in the winter. Ground squirrels like large expanses of fields and savannas, and I’ve never seen one in a small city yard. Furthermore, ground squirrels are true hibernators and sleep underground for several months of the year. So even if they did live in Saint Paul, they would not be out this time of year.”

Finally, Collin considers fox squirrel and gray squirrel:

"References suggest that gray and fox squirrel's tracks are very similar with fox squirrels being slightly larger on the whole. This track fits the range of both. Gait may be helpful in suggesting a species, but with a single track I'd have to go by habitat and odds. A ‘sidewalk in St. Paul’ suggests an urban environment. iNatrualist searches on fox squirrel sightings in the metro seem clustered along the Mississippi river. There are sightings in outlying suburbs, but mostly in large wooded areas as seems to be the preferred habitat for fox squirrels. So I'm going to have to go eastern gray squirrel as the final answer."

And with that, we arrive at our answer: the right hind track of an eastern gray squirrel.

Congratulations again to Ronnie, Robert, Collin, Maria and Erin. And a big thank you to everyone who sent in an answer and shared your process.

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