Tunnel time

The snow, so cold and lifeless itself, tells tales of unseen life. On an early morning walk after a fresh layer has fallen, you may see scores of tracks of all sizes and shapes, the record of creatures roving the night in search of food.

If the snow is not too deep or if it is melting, you may also spot narrow tunnels that curve, loop and zigzag under the crust and near the ground. They are a sign that shrews have been foraging for overwintering insect eggs and grubs. Tiny and weighing a fraction of an ounce, shrews are the hummingbirds of the mammal world. They live a high-speed existence, with a heart that beats up to 1,200 times per minute - 20 beats per second! To keep that machine going, shrews must eat up to three times their weight each day.

No wonder they wander in all weather. But unlike commuting humans, shrews probably like traveling in the snow. It helps hide their movements and sounds from the sharp eyes and ears of nocturnal predators like owls and foxes who might love a juicy shrew for a midnight snack.