May 2025 Natural Mystery Answered

Everyone who wrote in about last month’s Natural Mystery identified these as the tracks of an aquatic mammal. And indeed they are. Congratulations to Kate Campbell and new Track & Sign II, Haleigh, who correctly identified these tracks to species.

These are the tracks of a muskrat (Ondatra zibethicus).

Haleigh used a process of elimination to arrive at their identification. 

“I am seeing thin toes that do not have a wide pad at the tips, and a scant palm pad. This eliminates several groups of animals: leporids, canids, felids, mustelids, ungulates, ursids, and porcupines since none of these animals create tracks with long thin toes registering. With the rodents, lemmings, voles and mice are too small to leave this track. We'd expect the fingers to be thinner for a rat. I am not seeing the 1-3-1 pattern associated with squirrel hinds, who we would expect to be moving in a bound anyways. Woodchucks, raccoons, opossums and beavers would leave a wider toe impressions [in their front tracks]. We don't see the long claws we'd expect for skunks. That leaves us with muskrats!"

Kate began with habitat and track size to narrow down her candidates before digging into details of the track morphology.

"Proximity to the water suggests it could be beaver, otter, raccoon, opossum, mink or muskrat. All but the mink and muskrat I eliminated due to size of the track, which puts it around the size of these two animals. The tracks have strong registers of at least 4 toes with claws/nails at the end of them. The track immediately above the marker looks like a hind foot stepping on top of a front, obscuring the shape of the front track.

Looking at the track to the left of the marker, the front track registers above the hind, allowing us to see it in more detail. The front track is smaller than the hind, and the heel of the front track appears almost horseshoe shaped. This indicates muskrat to me. Mink front and hind tracks would appear similar in size, and would have a different shape to the front heel."

In addition to all these features, note the fringe of hair visible around each toe in the hind tracks. Unlike many other aquatic mammals, muskrats do not have webbed feet. Instead, they have stiff hairs on their toes that increase surface area to allow more efficient paddling. This fringe of hair is diagnostic, when it is visible in the tracks.

The track pattern is also typical of muskrats—a direct register walk showing short strides and a wide trail.

Congratulations again to Haleigh and Kate for correctly identifying these tracks. And thanks to everyone who submitted an answer to our May Natural Mystery.

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