Monday, March 2, 2015

Biology in the Snow

All through this deep Minnesota winter, I've been trying to think of some observations or discussion I could have about the biology of snow.

There are lots of interesting little things to learn about how living things deal with snow. Some plants grow roots into snow-banks to extract nitrogen before it is delivered to other plants in melt-water. Various bugs are specialized to deal with the cold and are active in and on snow. There are plants that heat themselves up in spring, melting away snow, so their flowers can get pollinated. I find these and many other things to be very interesting...  but it is difficult to go out and examine biology in the snow so I can have some direct observations to talk about.

The one exception is the observation of tracks in new snow. The photo at left shows the track left from a mouse scampering from near my front door (at right) to the top of my deck stairway (at left). As it bounded along, its larger hind feet landed ahead of the smaller front feet. This track doesn't tell a great deal, but it does highlight the amazing energetic feat of a tiny little rodent running around in the cold snow instead of freezing into a solid little mouse-cube.

You can learn a lot about what the animals are doing by reading their tracks.

A persistent mouse track-highway has revealed a well-used path between a rock-pile shelter and the base of a near-by blue spruce, where the mice are presumably foraging.

Other tracks have revealed the under-snow explorations of short-tailed voles. Many of these tracks become very obvious when the snow begins to melt. Long arcing paths are left as they forage for seeds and other tasty plant bits.

One time, I found tracks from a mouse bounding along the top of the snow crossing over the tracks left by a burrowing vole. The two rodents have very distinct methods of getting around in the snow. Mice hurry along from shelter to shelter, while voles tunnel along under the snow's surface. Both strategies minimize their exposure to cold wind.

Recently, the tracks of two coyotes revealed how they sauntered through the yard while one playfully ran around the other. I knew coyotes were in the neighborhood because we saw one crossing the road a few miles away, but I had never seen or heard them in the yard.

I've found the unique impression formed when an owl or crow lands heavily in the snow while trying to capture a burrowing vole.

Unfortunately, tracks in the snow can be very hard to photograph. You're trying to capture a white impression in white snow. The tracks are plain to see in 3D, but the 2D images from a camera are usually unclear. The mouse-track image above took several tries and then further post-processing to highlight the tracks that were immediately visible in person. Even after that work, I'm still pretty sure that the photo only turned out because the footprints were clearing away the snow to reveal the darker colored decking material beneath.

So, until I can figure out a good way to capture the images for presentation and discussion, all I can do is suggest you pay attention to the tracks being left all around you in the snow.

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