Just recently, the area has experienced the first snowfall of the season. A light dusting has spread over Hirundo leaving the refuge looking a little desolate. This first snowfall has given many wildlife insight into what is coming in the next few weeks. Once a few inches of snow have settled on the ground, a new microclimate is created which serves as an insulated habitat for many plants and animals. This microclimate is known as the subnivium and exists between the snowpack and the ground. It is formed when falling snow builds up on top of branches and ground vegetation creating airspaces. These spaces are warmed from the ground creating water vapor which will freeze the bottom layer of the snowpack, keeping it suspended from the ground. The subnivium creates an active place where plants and animals are able to live, eat, and travel under the shelter of the snow throughout the winter months.
First layer of snowfall on the forest floor | Field to Forest Trail
The temperature within subnivium is usually consistent throughout the winter, despite the freezing temperatures and winds that persist above. A landscape that may seem barren from above is able to promote the continuance of life due to these consistent temperatures. Many small mammals will find or create tunnels and shelter making this new environment their home. Plants, Insects, fungi, and invertebrates will all survive below the snowpack and provide food sources for these subnivium dwellers.
Larger animals that live above the subnivium have adapted to the new habitat of its prey. Some predators have discovered that they can burrow through the tunnels to find their prey while others listen for scuttling from above the snow and will pounce through to capture their prey. If you ever find yourself at Hirundo on a snow covered day, keep an eye out for the signs of this hidden environment. You might see things like the pouncing tracks of a fox diving through the snowpack or the tiny footprints of the vole that got away.
Check out the video below for an explanation of one wintertime predator adaptation for owls hunting in snowy landscapes.