February 2025 Natural Mystery Answered

Everyone who responded to last month's Natural Mystery identified the tracks as those of a carnivore--though the guesses covered five different species across two families. Answers also included a range of guesses about the source of the blood in the snow. Congratulations to Ronnie Hartman who correctly identified both the track makers and the source of the blood in this scene.

These are the tracks and sign of female wolf coming into estrus, together with the tracks of other members of her pack.

Here is Ronnie's succinct description:

"I believe we are looking at the prints and urine of a female eastern wolf showing signs of estrus by the blood in her urine, and possibly the tracks of a male that's courting her."

That is exactly correct. Let's dive in a little deeper together, beginning with identifying the tracks.

The scene included something of a jumble of tracks, but there are enough clear tracks for us to identify them with confidence. Using the ruler above the blood spot as a scale, we can measure the track just below that spot as at least 8.4 cm (3 1/4 in) long by 7.6 cm (3 in) wide, without claws. The track to the right of the ruler is even larger -- roughly 10 cm (4 in) long without claws. The tracks display the large toe pads, triangular palm pads, and star or X-shaped negative space typical of canids. The size and the stout nails identify them as wolf tracks. The number of tracks of different sizes suggests we are looking at a pack--another indication that these are wolf tracks.

The blood in the snow is from a breeding female approaching estrus. Breeding female wolves come into estrus ("heat") once per year. The onset of estrus is triggered by day length. In northern Minnesota, mating typically takes place in early February. In most cases, estrus is suppressed in the subordinate females in a pack. Like other canids, wolves have a period of proestrus before they are ready to mate. Proestrus is marked by an increase in estrogen levels and a bloody discharge in the urine. Proestrus typically lasts from 5 to 7 days, but can be as long as two months.

In this scene, it appears that the breeding female squatted to urinate. We can see her left hind track next to the ruler on the left, and her right hind track at the same level on the far right side of the photo. The large track to the right of the blood spot is most likely form her mate. Tracks of other members of the pack are mixed in across the scene.

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