This picture was taken on the same early March trip to central Washington as last week's mystery.
The Questions:
For all of these questions, you may want to click to enlarge the picture to get a good enough view.
1. What is the predominantly used gait?
It is difficult to tell what gait is used where the tracks are all overlapping on the trails, but pretty much everywhere that individual sets of tracks are visible the animal is moving in a bounding pattern.
In the close up picture, the tracks toward the bottom are the front feet, toward the top are the hind. Notice how the back feet are in line with each other, they need not be exactly aligned but this alignment is part of the definition of a bound. The front feet can be more or less aligned.
A bound is a subcategory of a gallop though in my experience it is rarely discussed as such.
In the close up picture, the tracks toward the bottom are the front feet, toward the top are the hind. Notice how the back feet are in line with each other, they need not be exactly aligned but this alignment is part of the definition of a bound. The front feet can be more or less aligned.
A bound is a subcategory of a gallop though in my experience it is rarely discussed as such.
2. What species? (or as close as you can get)
The gait, size and foot morphology point to a small rodent. Most rodent species show four toes in their front tracks and five in their hind. It may often be difficult to see this exact count, but one thing that often is visible is how in the hind foot there are three aligned toes more or less pointing forward. The other two toes point of to the sides and are sometimes less visible. The four toes on the front foot are often more evenly spread apart.
One of the things I find most useful when trying to identify unfamiliar tracks is having a master list of species for that area that I can work down from. Most of the animals this size that come to mind are rodents, but there certainly are other types of animals in this size range including shrews and lizards. Shrews are actually even smaller than this though and I have a hard time imagining a lizard moving in a bound. In this region though there are quite a few potential rodent options. Broadly there are (potentially): pocket mice, kangaroo rats, pocket gophers, wood rats, voles, deer mice, harvest mice and grasshopper mice.
Wood rats, kangaroo rats and pocket gophers all have tracks noticably larger than these. This is not a habitat I would expect to see voles, they seem to hang out largely in grassy areas rather than dry sandy patches like this. Pocket mice (closely related to kangaroo rats) moving in a bound often have their front tracks overlapping rather than separated as is the case in most of the visible track patterns here, they also have a narrower trail width (I think the trail coming from the lower middle portion of the picture and exiting mid right may be that of a pocket mouse). Peterson's Mammals field guide says western harvest mice are usually found in dense vegetation close to water, so again this habitat doesn't quite fit. I've found no information on grasshopper mice tracks, so I can't rule them out. But I think the best fit is the deer mouse.
Deer mice are common in this habitat (and many others). The toes of their tracks are generally bulbous (compare with voles whose toes tend to show up more thin and finger like.)
I'm impressed by the amount of traffic evidenced here. I wonder if it was more than one mouse. I imagine that a single mouse could make such trails, but it was late winter so there could be breeding mice sharing a place or mice sharing a place for warmth at night.
3. Why are there sections in the middle of the heavily used paths that only have a couple sets of tracks in them?
I was pretty puzzled when I came upon these tracks. I imagined little mice full of bravado running up towards each other, but stopping in time to maintain a safe distance. They would taunt and threaten and run back. Occasionally one would boldly cross the gap to the other's side to show what a brave fellow he was.
This hypothetical posturing didn't seem very likely to me though.
If I recall correctly, I got the hypothesis that I think is correct from Dave Moskowitz who is the lead tracking instructor at Wilderness Awareness School (I was out as part of WAS's tracking intensive class when I took these pictures.)
If you imagined the major paths to continue straight across the gap then this picture would be easy to interpret: there was a mouse (or mice) going back and forth along a couple of major trails. If you assume that the major paths generally did not connect up (except in the couple of sets of tracks that span the gap) it would be much more difficult to put together. Why would a mouse be stopping suddenly in the same spot over and over?
So let's start by supposing that the trails generally do connect up and for some reason we aren't seeing most of the tracks in the gap section.
One possibility is that something moved through the gap section and wiped out most of those tracks and the mouse ran through afterwords a time or two leaving the gap tracks that are visible. This hypothesis seems to be supported by the fact that the main trail has a variety of agedness while the gap tracks seem to be fairly fresh. However the area seems quite smooth, so it is a little hard to imagine something went through there wiping tracks clean while leaving so little disturbance behind it.
Some people mentioned in the comments that it seemed like there might be water involved. There certainly is water not too far away - there are lots of little ponds spattered around, but overall it is a pretty dry place (as evidenced by the sand and vegetation), so I don't think there was running or standing water in the area pictured anytime close to when the picture was taken. This was however taken in early March and it tends to be pretty cold at night in the desert. So what I think happened is that the gap portions of the trails were frozen during the night. Presumably small scale topographical features allowed the gap areas to have more moisture which froze hard enough that the tracks did not register until it started to warm up. This would also help explain the crispness of the gap tracks as they would likely have been made as the sand was still damp. The gaps were not more heavily tracked up after the thaw because as the sun comes up the mouse becomes less active, so probably went back to its nest for the day
The last question is one I may have still been puzzling over if I hadn't been working on it with other people. I'll be interested to see what ideas you all come up with.
I'm adding the picture below in the hopes that it will be helpful. I'm not sure that it will be any more helpful than the picture above, but at least you will be able to see a closer view of the individual tracks.
Previous Next
6 comments:
That's funny, I just took about a million pictures of these same tracks in the Oregon Dunes a couple weeks ago. And I'm a little embarrased to admit that I don't know what they are. A small rodent, for sure, but I don't know what sort of little mouse/rat/vole lives in that sort of habitat, although apparently whatever they are, there are approximately 4.7 shittons of them in the Oregon Dunes.
I was surprised to find neither fox nor coyote tracks where I was in the dunes, since I'd think this was a canine smorgasbord. Probably they were there and I just didn't find them.
There were the same gaps in trails where I was too. I hadn't actually pondered it, but now I'm guessing that those gaps happen on inclines where the little guys jump up and down each time.
I always forget the words for the various gaits, but I think the ones that I saw were mostly in the same gait as a rabbit, where the two front feet come down first, often slightly off from parallel, and then the back feet register right next to each other just ahead of the front feet.
Yeah, I think this species is the same as (or closely related to) a species as the dunes.
One of the most useful tools I've found for identifying tracks I'm unfamiliar with is to create a master list of possibilities. Of course one of the most effective ways of doing this is looking in a field guide or at online resources where you can figure out exactly (more or less) who lives there. You can do it more informally as well, such as Deanna's "mouse/rat/vole". One potential problem with that route is you can miss species you weren't aware of. Since I began tracking more seriously, I've learned of several species I'd never heard of. That said, I think that this species is one of the more common ones. But central Washington does have a lot of cool little rodents that it would be worth exploring if you have any interest in the area.
I'm also surprised you didn't find fox or coyote tracks. Seems like they have been among the most common tracks I've seen when I've been down there. I wonder where they went? Was there any unusual weather (or unusual anything else) going on while (or shortly before) you were down there?
I used to have difficulty remembering gait names too. Great that you know the body mechanics though! Just the other day I decided to look at some animal videos on youtube and I found some cool examples of animals doing a 2x2 walk which was the first time I really understood how the body was moving differently than in a diagonal walk.
Originally I was thinking the gaps were due to slope hopping as well. I was going to say something about how difficult it was to determine the topography from the photo. However, I realized that even if the widely spaced tracks are due to a slope, it seems pretty clear that there are not enough tracks there to account for all the tracks in the higher density areas. In other words, the gaps had far fewer animal crossings than the dense part of the trails, though it's not clear to me why.
Another idea I had is that something came along and erased tracks. It does appear that the dense tracks tend to be older and/or made in dry sand while the tracks in the gaps look like they were fresher and/or made in damp sand. Perhaps a depression was filled with water when the bulk of the tracks were made? Again, the difficulty of evaluating the micro-topography makes it hard to figure out if that's reasonable.
It seems like this one may be more difficult than I had thought. I would like to challenge people to come up with 5 species they think the tracks could have been made by.
I would also like to hint at the last question: Considering the relative ages of the tracks is probably a good idea.
They look like woodrat tracks to me. I would guess bushy tailed? The gap in the trails is strange because the camera kind of warps the edges of the picture, so I can't grab any sense of perspective, but it looks like the gaps are part of a snaking trail. I don't see any signs of drag, and the plant stalks are not bent or broken, so I would have to rule out any animal or any object lying across the tracks. It looks like an area of water flow. The crack seems to back that up, too.
At first, I didn't see the sneaker tracks in the upper left corner, so the perspective looked like an aearial view of deer beds and snowshoe hare trails. Then I realized that the "deer" or "moose beds" were actually another footprint and what appear to be elbow or knee prints with extra weight being on the right (uppermost) knee/elbow as if someone was getting a better angle on the tracks or for a photo. From the footprint, the next track should be in the plants, and I think I see it, but I'm not sure. I'd like to know what the blue object is on the left side of the photo, too.
It does look like there is a (human) foot print in the vegetation near the bottom, though the plants don't look particularly damaged. I'm not sure if that is the next track, and if not where it might be.
I'm also not sure what the object is in the upper left corner (I am assuming that is the same one you are referring to Quigley), though it looks like a bit of trash to me.
Post a Comment