Track and Hair Analysis: An Intermission

You’re the doc, Doc. – Back to the Future

When we went on our earlier adventure and retrieved the videos of squirrels and mice from our trail cams, we also got lucky and found some tracks, along with what we thought were hairs stuck to our contact paper. So, being the researchers we are, we decided to analyze our results a little. What kind of animal made the tracks? What kind of hairs were these? Were they from the same animal?

Tracks

For reference, here are our two track stations.

The top strip of contact paper has cleaner tracks than the second strip.

So, using these fantastic field guide tracking books. . .

These kind of books will be your good friends out in the field.

We decided to try and first identify the animal that made the tracks. We considered a few species of rodents; the deer mouse, also known as a white-footed mouse (Peromyscus), and the Southern red-backed vole (Clethrionomys gapperi). Unfortunately, we had to rule out the possibility of the tracks coming from a shrew because each individual track only had 4 digits, whereas shrews typically have 5 digits. Upon further examination under the microscope, we noticed that the soles of the animal had 3 main padded regions with 2 extra pads at the heel. The deer mice tracks we saw in our books had more this characteristic.

Under the microscope, you can clearly see the 4 digits, the 3 padded regions, and the 2 back heel regions. These are characteristic of a deer mouse.

The vole tracks we referenced had 4 padded regions with 2 small, extra pads at the heel. Additionally, upon doing a little extra digging we found that this particular species of vole was not naturally found in Southern Utah, only Northern Utah. With all this data, we had to assume that the tracks were in fact from some species of deer mouse. And with that, the mystery of the animal behind the tracks was solved. Considering how common deer mice are in our area, it’s not that surprising to find our perpetrator’s tracks belong to this wide-eyed mouse.

Hair

We were most excited about the hair that we found stuck to our contact paper. Sure, we would have rather the hair be stuck to the actual tape (lint, packing, or duct), but we weren’t going to complain about this small victory. Since hair snare traps have a low success rate, only about 20%, and since we only set out 9 traps, we were excited to have any samples at all, regardless of where they were on the trap. We took the strip of contact paper back to the lab and proceeded to carefully prepare our samples. Using specialized tweezers, some ethanol, and a slide and slide cover, we extracted a good 5-6 hairs from the contact paper. We then prepared them and proceeded to look at them under the microscope. And you know what we saw?

Exhibit A
Exhibit B

What appeared to be hairs as seen by the naked eye were actually arthropod limbs. You can see the joints in the first picture, definitely not something you would see on hair strands. And if they were hair strands, why would there be hair on top of hair (as illustrated by the second picture)?

Not only that, but these samples look nothing like what hair normally looks like under the microscope. Normal hair has ridges and grooves that appear almost like scales, as shown below:

Normal (non-damaged) hair has overlaying sections that make the hair smooth. Image courtesy of microlabgallery.com

Piecing it all together, it seems that some unfortunate arachnid might have crawled into the tube and gotten trapped by the contact paper meant to imprint tracks. Then, in a desperate fit for survival, that unlucky fellow might have decided he was better off losing a leg or two rather than starve to death. Pretty gritty stuff, right?

The amount of samples we found on the contact paper were all varying sizes, which leads us to believe it was more than just one type of arthropod. Maybe some beetles, ants, flies, or other insects got stuck inside and had to become amputees to survive as well. Our camera was not able to record that action, so we’ll never know for sure, but we’d like to think some brave insects are wandering around there with missing limbs, all in the name of science.

Unfortunately, for us this means we were not able to obtain actual hairs from our hair snares. We haven’t given up though; it’s merely back to the drawing board to try and design a better, more efficient small mammal hair snare trap.

Until then, we’ll see you in the next post!

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