Exploring and Speculating in the Snow

Snow is a great boon to anyone trying to figure out what’s happening in the prairie during the winter. I’m just a casual observer, not a researcher of winter activity, but it’s definitely a topic of interest. A fresh snow fall provides a chance to look at tracks and try to interpret what’s happening.

Last week, I saw a couple interesting things in nearby snow-covered prairies. The first is something I’ve seen often before, which is evidence of the importance of western ragweed as a winter food. Ragweed plants sticking up above the snow are very commonly surrounded by bird tracks, and I saw lots of that at our family prairie last week.

Western ragweed (Ambrosia psilostachya) sticking out above the snow last week, showing the large nutritious seeds just sitting there ready to eat!
Bird tracks around western ragweed plants.

I know people tend to scoff at, or actively dislike ragweed, but it’s hard to dispute its value to wildlife. I understand those of you with severe allergies to ragweed pollen not being fans. Beyond that, though, it tends to get an undeserved bad rap from farmers/ranchers who mistakenly think it is aggressive and outcompetes grasses. The reverse is true – its populations expand when the grasses are weakened and shrink when grasses are strong.

Others dismiss it because it is a ‘weed’ and/or doesn’t have showy flowers to attract pollinators. Sure, it’s very common, and perpetual high abundance can be a sign of poor prairie management, but it’s also a native plant that plays an important role in grasslands. In addition to its ability to fill and temporarily hold space when the surrounding plant community is stressed, it’s impossible to dismiss the attractiveness of its seeds to wildlife. If you have any doubt, look for ragweed plants the next time you’re in a snowy prairie. Most likely, you’ll be able to follow tracks right to them!

Here, you can see both bird tracks and a few dropped seeds below the plants, where birds were pulling other seeds off to eat.

The second interesting thing I saw last week connects to another observation earlier this year. Back in April, I was walking through a recently burned area at Prairie Plains Resource Institute’s Gjerloff Prairie and found a pile of seeds I’m pretty sure were from marbleseed, aka false gromwell (Onosmodium molle). They might also have been from fringed puccoon (Lithospermum incisum) – the seeds of those two species are awfully similar.

Seeds at Gjerloff Prairie after a spring prescribed fire. I think these are from marbleseed, based on their size, though they might have been puccoon seeds too.

The way the seeds were gathered together made me think it was a seed cache, created by some kind of mouse the previous year. The fact that it was still there after the winter made me wonder if the mouse didn’t survive (or just didn’t find its cache). Either way, it was neat to see and fun to speculate about.

Last week, at our family’s prairie, after perusing the bird tracks around ragweed plants, I came across a mouse trail that led to a small area where it looked like the mouse had dug down to the ground. The tracks led pretty directly to the excavation site, making me think the mouse probably knew where it was going (as opposed to just wandering/foraging randomly).

Mouse tracks and an excavation.

Looking closely in the hole, I saw some seeds that looked just like the ones I discovered at Gjerloff Prairie back in April. Aha! More evidence. I know mice create seed caches, but I don’t know much about what kinds of seeds they might store, where they store them, or how good they are at finding them later. If anyone can enlighten me on this subject, I’d love to hear from you.

Here’s another photo from a little closer to the hole. I used Photoshop to open up the shadows and show the details inside the hole, and you can just barely see a few remaining seeds at the bottom. (Click on the image to see a closer view).

Just based on observation and speculation, it looks to me like some small mammal harvested and piled some marbleseed/puccoon seeds up – presumably in the early to mid summer when those seeds were ripe. (Based on a lot of years of seed harvesting, those seeds disappear from plants pretty quickly after they’re ripe – probably because of mice!) Then, on a sunny day after a snow, that same mammal (?) appears to have trekked across the snow and dug up the cache. Did it know exactly where it was? Based on the tracks, it sure looked that way to me – either that or it somehow smelled the seeds beneath the snow. One way or the other, I’m impressed.

As I said at the beginning of this post, I’m no expert on winter survival, especially by birds and small mammals. I do, though, enjoy trying to figure out what I can learn through observation, and snow is really helpful in that venture. Last week’s snow is melting fast now, but I’m hoping for a few more chances to explore later this winter. If anyone can help me interpret what I saw in these photos, I’d sure appreciate it!