Friday, February 4, 2011

Subnivean Space, Part II

  You may have guessed what happened here. 
  Just the other day I saw a Red-tailed hawk standing in the snow, intently looking and listening for its hidden prey.  I wish I would have had my camera.  The markings it left in the snow would be similar to the ones pictured above.  These look like the evidence of a bird of prey crashing the subnivean space down around a mouse or vole, then grasping around in the snow to capture it. Then, as the bird took off, it left the signature mark of its primary flight feathers.     

Subnivean space
   
Subnivean means "under the snow".  This is the space beneath the insulating snow pack that mice, shrews, voles, and some insects live sheltered from the winter cold and out of sight from predators.  The subnivean space is a labyrinth of small openings, "a snow cave", that has a fascinating way of developing. The book, Life in the Cold: An Introduction to Winter Ecology, by Peter Marchand, details this changing snowpack. 

Below are some pictures of the snowpack and a few words about is characteristics.
The snowpack starts out as fluffy delicate snowflakes.




  Soon those snowflakes are changed into more densely packed, rounded particles.  Heat from the ground vaporizes some of the snow, forming air space and loosely packed crystals at the base of the snowpack.  These cup-shaped, faceted crystals are called depth hoar.


Depth Hoar

By the way, this is a hand-held shot (in the dark with a flashlight) with my Pentax Optio W90 pocket camera.
Depth hoar crystal.
The clear, layered wedding cake looking crystal, in the lower left is a fairly good picture of a tiny depth hoar crystal. Down close to the ground, these brittle, loose crystals, along with the space from the melted snow, help provide a comfortable habitation for many little creatures.

Snow "blankets" the winter world with beauty. 
Snow "covers" an amazing amount of activity.
Snow provides "comfort" to a variety of wildlife.
I hope this post added the subnivean space to the patchwork "quilt" of your understanding of the winter world around you.



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