December 2019 Natural Mystery Answered

Our December Natural Mystery was a bit of a trick question--but many of you were quick to see through the charade and correctly identified the critter that left this track. Congratulations to Chris Albert, Thom Bergstrom, Kim Cabrera, Paul Glasser, Rob Grunewald, Amy Manning, Megan, and Kirsten Welge who identified what species made this track.

This is the indirect-register of a domestic cat. The photo shows the left-side tracks--with a single toe from the front foot showing next to the full print of the hind. Let's get into how people worked this out.

Many of you began by considering, then eliminating, other candidates. Amy Manning points out that all of the local mammals that leave 5-toe tracks in this size range (such as skunk, mink, or a small raccoon) show distinct claw marks. While Thom Bergstrom succinctly states that the print "just didn’t look right for me as a mustelid."

Paul Glasser noted that "The print was in snow and I could see the fur imprint all around the track, meaning that what showed as the heel pad was all there was to the heel." Based on this, Paul eliminated species that have a longer heel that may register inconsistently, such as skunk, raccoon and marmot.

Kirsten Welge adds some more detailed notes distinguishing what we see here from weasel and skunk tracks:

"Weasel tracks show more negative space between toes and palm pad. Mustelid fronts will show more radial symmetry while mustelid hinds will show a more canid-like 'boxy' shape, with a larger gap between toe 2 and toe 1. In a skunk track, I'd expect to see claws registering in front of the toes. The toe structure doesn't match, either."

With these fived-toed animals eliminated, we need to consider other possibilities. And, as Amy points out "If you cover up the toe nearest to the ruler, this looks like a classic cat track." Kim Cabrera, Rob Grunewald and Kirsten added a few more details about what makes this a classic cat track:

"The negative space is C-shaped and the metatarsal pad is large related to toe size. Size is consistent with domestic cat. Bobcat would be larger. The leading toe shows that this is from the left side of the body." -Kim

"The toes form a C-shape with a prominent palm pad, no claws showing, which is characteristic of a domestic cat. Left side in part because the second toe from the right side is longer than the third toe." -Rob

"The track shows a large, slightly distorted M-shaped palm pad, C-shaped negative space and five small, teardrop shaped toe impressions. Toe 3 is the leading toe for felids, making this a left hind print." -Kirsten

And, indeed, this is a domestic cat track. But cat tracks typically show four toes, not five. There were two different explanations offered for why this particular cat track might show five toes. As several people noted, domestic cats sometimes have extra toes. As Rob Grunewald shares:

"Cats can have extra toes, either polydactyl or feline radial hypoplasia. For polydactyl cats the extra toe(s) are separated from the normal ones like a dewclaw, while cats with radial hypoplasia have extra toes right next to the normal toes, which looks like this picture, one extra toe on the left side."

Kim Cabrera considers extra toes, and offers another explanation:

"One possibility is that this is a polydactyl cat, with five toes. But, I think this one is not a polydactyl cat. I think it's an overlap of prints because of the angle of that outside toe, which is from the front foot. The rest of the front track got obliterated by the hind track, which landed on top."

Kim is correct right that the arrangement of the toes isn't a fit for a polydactyl cat. But what about radial hypoplasia? I know for sure that this is an indirect register, because I was able to see the entire trail, but the photo only shows this one track. I am not familiar with the foot structure caused by hypoplasia in cats, so I don't know if we can rule that out based on morphology alone. Based on a little research, however, I think we could consider it highly unlikely. Feline radial hypoplasia describes the severe under-development of the radius (forearm bone), which can lead to the animal growing extra toes. Cats with this condition have abnormal posture, often sitting up on their hind legs like a squirrel. The condition is considered a fairly serious genetic defect, and caretakers of such cats are advised to keep them indoors and consult with a specialist veterinarian to provide the long-term management of their condition that is essential for good quality of life.

Thanks to everyone who submitted an answer, and congratulations again to Chris, Thom, Kim, Paul, Rob, Amy, Megan, and Kirsten for identifying this very unusual feline track.

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