Rat Tracks

The last three days I have gone down to my tracking spot under the bridge and found fresh rat tracks. I've seen rat tracks there previously, but never this frequently and never as many as this. The first two days were actually pretty similar to the rat trails I've seen before except there were fresh trails on consecutive days. Today there were a lot more trails so I wonder if a rat decided it was a nice hangout lately and brought his friends back. I didn't see anything that convinced me that it was multiple rats interacting, but it seems reasonably likely to me that it was more than one rat.

I wonder why the sudden increase in rat activity there. The river had been relatively high within the last couple of days and has since been receding, but much of the rat activity occurred above where the water reached, so I don't know that it was due to the change in water levels. I didn't notice them to be focused on any particular thing (like the stinky salmon corpse rotting nearby). Nor did I notice them feeding on anything, though it's possible I just missed them picking up insects or whatever.

I'm not sure whether it was a black rat (Rattus rattus) or a norway rat (Rattus norvegicus). Elbroch has norway rat tracks in his book, but not black rat and I didn't find any useful information about black rat tracks on a cursory inspection of the Internet. It is my understanding that both species live in this area.

I guess I could try and get a glimpse of the rat as it is making the tracks, or live trap one, but I'm not sure I'm quite motivated enough to do that at this point. However, if anybody has information on differentiating between the species, please let me know.





It's interesting to me how different these tracks look despite being from the same animal. I would guess the difference is due to substrate.

Olympic Peninsula Tracking

Last weekend the tracking intensive (a class through Wilderness Awareness School) went over to the Olympic Peninsula. It turns out to have been a fortuitous plan - last year we went to the east side of the cascades for our snow tracking weekend, but the pass was closed this weekend. The weather in the Olympics was beautiful. The fog was burning off as we approached Hurricane Ridge and the sun was shining as we began snow shoeing.

Along the way we saw numerous snow shoe hare (Lepus americanus) tracks (some folks in the other group actually saw a hare), douglas squirrel (Tamiasciurus douglasii) and long-tailed weasel (Mustela frenata) tracks. There was some question as to whether some tracks we saw were long-tailed weasel or pine marten (Martes americana).

In one set of tracks you could see where a squirrel had plopped several inches into the snow after jumping out of a tree. It then tunnelled back up to the surface and hopped away. In trailing it backwards I saw where it had done the same thing from several different trees. I wonder how it learned to do that - did it happen by accident once and it discovered what fun it was to jump out of trees? How does it know when there is enough snow that it is safe?

We spent much of our time trailing a weasel - unfortunately none of my pictures of it's tracks turned out particularly well. It was fun to get a chance to follow its path moving tree well to tree well along its way. At one point we lost its tracks as it went into the snow under a downed tree. Eventually we found its trail again 50 feet away coming out of another gap in the snow by another log. Just a few feet later it disappeared again down a tree well and we stopped searching at that point. It's interesting to think about there being a whole subway system beneath the snow that small animals have access to.

The next day was mostly overcast, but was a good day of tracking. We stayed at low elevation and looked in areas where some fishers (Martes pennanti) were recently released as the first in a reintroduction program. We didn't find any fisher tracks, but we did find numerous bird, shrew (Sorex sps), deer (Odocoileus hemionus), bobcat (Lynx rufus), and spotted skunk (Spilogale gracilis) tracks.

As we drove through the park towards our destination we saw several trails in the snow along the road. We resisted for a while, but eventually the draw became too strong and we stopped and got out (it was the spotted skunk tracks that put us firmly over the edge).

We had the beautiful trails of three different species criss crossing right in the middle of the road. At first I believe most of us thought the skunk was actually a weasel. After some time looking at the tracks, Dave (our instructor) challenged us to look closely at the tracks (the ones I thought were weasel) and decide what we thought they were and why. Not long into the exercise Dave exclaimed that he had changed his mind about what we thought it was. That gave me pause as I had not had any strong question about what it might be. The feet looked a bit strange for weasel, but the gait was completely wrong for squirrel and there is nothing else in that size range that might be in the area, right? (This is the same sort of thinking I had when I ran into a spotted skunk hole earlier in the year.) Dave then suggested we sketch the tracks. I'm generally pretty averse to sketching tracks (not sure why), but everyone else was doing it and I was otherwise mostly standing around waiting, so I got my sketch pad out and sketched. It wasn't until we were gathered sharing our sketches and the difference in claw size on the front and hind tracks was mentioned that I realized they were probably skunk tracks (skunks are generally diggers so have bigger front claws). Dave confirmed, pointing out a few more characteristics that differentiate them from weasel tracks - one such being that the middle toes are partially fused and so there is much less splay in the tracks. I definitely need to start including skunks into my mental list of possibilities for western Washington.

Holiday Exploration

On Monday afternoon I went up the middle fork of the Snoqualmie to do a little exploration. It's been awhile since I've just done some good wandering so I thought that's what I would do.

As it turned out I ended up doing quite a bit of tracking as well, but that's okay. It had been cool and clear for a couple of days and there was still an inch or three of crunchy snow on the ground. As I drove along I kept an eye out for things of interest, finally stopping where I saw some largish round tracks going off into the bushes. A cougar? The tracks weren't particularly clear, but as I saw more of them I think it was more likely a dog. However there was a ton of bobcat tracks back there. It was hard to be sure, but it looked like maybe a couple of different individuals - perhaps a breeding pair, though I didn't notice anything conclusively indicating interaction between the sets of tracks. I did see some interaction between the tracks of a bobcat and a hare though. The bobcat had taken several powerful strides, right in line with a bounding hare, but it appeared that the hare got away without too much difficulty.

After exploring that area I continued on down the road and stopped off at a place I had gone before with the tracking intensive. Downhill from the side of the road is a little creek and some marshy and wooded areas. I saw some more bobcat tracks on the near side of the creek, but none on the other side. For quite awhile the only tracks I saw were some mostly buried deer tracks - until I heard some loud crunching up ahead. I looked up and saw an elk looking at me, then turn tail and head off. I didn't notice any antlers so I think it was a cow. I went over and investigated - it appeared to have been coming in my direction until it saw me and headed back more or less the way it came. The snow was quite loud so it must have heard me well before it saw me. I guess it wanted to see what I was before deciding what to do.

I didn't want to follow it very closely because I didn't want to cause undo stress for it in the winter season. I would have liked to just back trail it, but since the fore trail and back trail were the same direction, I just slowly followed it looking to see what it had been doing. I saw a couple of places where it had browsed some brush (though I don't remember what kind of shrub it was). Then I heard some more crunching across another branch of the creek. I looked over and saw another elk looking at me. This time I think it was a bull. It was a hard to be sure though with such a brief glance and looking through a lot of branches. I stood still and watched for awhile and heard a lot of walking one direction and the other. I had thought that it was the elk going back and forth, perhaps not too worried about me across the creek, but it may have been that there were several elk up there going in different directions.

Since I had been thinking it was a single elk I thought it might still be up there, so after a while I slowly crossed the stream (on a log) and carefully approached where I could get a better view, but the elk were gone by the time I was in a position to see much more. Since it was getting towards dusk I wandered back to the truck - once hearing another elk off to the side.

Mole Tracks!

Tracking club was very wet yesterday. Out at the sandbar a lot of our tracks were being quickly worn away as we studied them. Still it was a good day there - we found many species with some nice clear tracks (at least before it started raining). Our group was small and with the rain we decided to go somewhat quickly through the tracks there and then stop under the bridge on our way back.

While we were looking for tracking stations before tracking club got started we noticed some mole hills and tunnels. The story in our tracking community seems to be that protruding tunnels = coast moles (Scapanus orarius) and large mounds = townsend moles (Scapanus townsendii). Sometimes we find areas where there are several mounds and tunnels. What then? This is a subject that probably needs some more investigation.

Anyway as we were driving down to the bridge Dave and I discussed this a bit as well as about finding mole tracks. Apparently the spring dispersal is a decent time to find mole tracks as they are kicked out of their homes by mom and have to go find someplace new. It is a bit early in the year for that though. However, as I was looking at tracks under the bridge I noticed a pattern that seemed similar to what I had heard described and had seen pictures of as mole tracks (I had never seen them in person). Excited, I called over a couple other station leaders to confirm and all were surprised and in agreement that they were indeed mole tracks.

I haven't found much in the literature about differentiating moles by their tracks, so I don't have any good idea which species it is. One possibility I've thought of (though I have no idea if it is at all reasonable) is that the mole was out for the breeding season. Peterson's Field Guide for mammals says that male coast moles are in breeding condition in late January and townsend moles in February. Based on those dates if my theory is true it would seem to be a coast mole. However those dates are not too far apart and I would expect there to be a lot of regional and year to year variation in breeding dates.

(You should be able to see the tracks a lot better in the first and last picture if you click to enlarge them.)

Skulls

While visiting my parents in Idaho this Christmas, I went down a canyon with my dad. I've been taking a greater interest in bones lately so I gathered a bunch of them when I found a big set of owl pellets and a few bones along the edge of the canyon. My dad also found a nice skull under a bush while fishing along the creek.

Now that I'm back home and have access to my copy of Elbroch's Skulls book I've been looking over the skulls and figuring out what they are from. So far I believe I figured out the two here to genus at least, and know that there are at least two other species in the collection.

There are a lot of details visible in these pictures that can be used to figure out who the skull belonged to, but it would be difficult to go through very many of them. Instead, I will just go over a few of the main details I used. For reference the first skull in each pair is about 6.5 cm and the second skull is about 5 cm. Both are clearly rodents from the teeth, so I'll go from there.




The first skull ended up being pretty easy for me to identify because of its size and the way the brain case sticks out squarely over the eye socket. Just flipping through the pictures of skulls I saw that it matched up with the muskrat (Ondatra zibethicus).

The second skull has a well developed post orbital process (the sharp protrusion over the eye socket). As far as I can tell, among rodents, those seem to mainly occur in the squirrel family.




At first I thought the second skull might be a type of marmot because of the shape of the post orbital process (and because they are large members of the squirrel family). However when going through the details of the marmots things kept not seeming to match up quite right. What finally convinced me that it wasn't a marmot was that marmot skulls are pretty flat on top, somewhat similar to the muskrat skull, however this skull is fairly rounded. In hind sight the skull was smaller than the range given for marmots as well. With a little more searching, I found that ground squirrels (Spermophilus sps) fit the skull much better.

A couple of differences to note are the position of the zygomatic arch (the bone that forms the outer portion of the eye socket) and how curved (or straight) the incisors are. I don't know that these are more useful details to pay attention to than others, but they seem fairly easy to pay attention to.




A couple of differences I notice on the ventral view are the size and shape of the palate, the relative position of the teeth (including parallel vs. angled) and the size and position of the incisive foramina (the narrow pair of holes behind the incisors).

I have not yet got down to species on the ground squirrel. There are a couple of different ground squirrel species in that region of Idaho that aren't in the skulls book and the skull doesn't seem to match up exactly with the ones that are.