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April 2018 Natural Mystery Answered

posted May 18, 2018, 11:47 AM by Jonathan Poppele   [ updated May 18, 2018, 11:48 AM ]
We received a number of correct answers to our April Natural Mystery. As Kim Cabrera, Rob Grunewald, Brendan White, and Charlie Perakis all suggested, these are the tracks of a jumping mouse--a member of the family Dipodidae. Congratulations to all four of you. Kim and Rob also offered clear explanations of their process, pointing out identifying features and distinguishing characteristics of these prints. Kim starts us off with this break-down:

I identified these as the tracks of a jumping mouse, either Zapus or Napaeozapus, based on the following characteristics. The hind tracks are the two to the outsides in this photo, and the fronts are the two in the middle. The hind tracks have five toes, with a narrow “neck” where the three middle toes converge. (Toes 2-4) They have long, skinny toes. The orientation of the hind foot’s toes is also typical of jumping mice. There are two pointing to the sides, toes 1 and 5. Then, three pointing mostly forward, and grouped together. The three middle toes have a sort of fan-shaped orientation when looked at in isolation from the other toes. The front tracks show four toes, with long skinny toes. The toes are not oriented in typical rodent fashion, which would show two pointing outward and two forward. In jumping mice, the toes are more asymmetrically oriented so that 2 and 5 are not right across from each other if you draw an imaginary line across. The toes are not bulbous at the end, like in Peromyscus. Size is consistent with mouse tracks. Very small. Claws are not seen here due to substrate.

Rob Grunewald takes his analysis a step farther, bringing in habitat and range to offer an identification to species. While the tracks themselves to not allow us to distinguish between genera of jumping mice, Rob's analysis is likely correct:

Meadow jumping mouse. The size of the feet and trail width are on the smaller side for a jumping mouse. The palm pads are not registering much; jumping mice have relatively narrow palm pads. The toes in the left front track (the most visible of the smaller front feet) are irregularly spaced and the outer toe is set further back, characteristic of a jumping mouse. Toe 2 on the right hind track is long, slender, and bends out toward the left, also characteristic of a jumping mouse. Toe 1 on the right hind track is set further back. Toes 2 to 4 on the hind left track are not as irregular as they can be on jumping mice, but the tips of the toes on both hind tracks don’t make a straight line across the tips like they do for many other mice. Also, for bounding mice, such as harvest mice and white-footed mice, the front feet are often next to each other instead of one in front of the other. For jumping mice the feet position vary, including this one-foot-in-front-of-the-other position as we see here. Other possibilities to cross of the list: The tracks are too large for a shrew, particularly the hind feet. Front feet in this picture seem to have 4 toes, shrews have 5. Voles tend to trot, not bound or lope, across open spaces. Woodland jumping mice also live in Minnesota, but orient more to forests in the northeastern part of the state.

Big thanks to Kim & Rob for sharing their knowledge with us!