Life in the Cold

During a winter walk, the woods may seem so quiet and still, and it’s easy to think that there is very little activity happening this time of year among the plants and animals at Asbury Woods. While some species do escape Pennsylvania winters by migrating, many more remain with us all winter long.

Active animals

Many predators native to western PA like foxes, weasels and owls can stay active despite challenging conditions that winter brings because they are still able to locate and hunt their favorite prey.  The red tail fox is especially talented at this, being able to detect mice under a blanket of snow, leap into the air and pounce on their prey.  Foxes can hear very low-frequency sounds, enabling them to hear rodents scampering beneath several feet of snow. Scientists also believe that foxes tune in to the Earth’s magnetic field to hunt: as a fox follows the sound of its prey beneath the snow, it’s searching for the “sweet spot” where the angle of the sound matches the planet’s magnetic field.

Owls also have impressive abilities to hunt in snowy conditions.  While we might not see them in action as owls are nocturnal. However, you might spot the impression of their wings and tail feathers in the snow, a clear sign of a nighttime hunt.

The short-tail the long-tail weasel are among two most common species of weasels in western Pennsylvania. They employ a clever trick to help with their winter survival – putting on white coat.  In the spring, summer and fall they sport brown fur with white underparts, but for some, the shortening days will trigger their coats to turn white, providing the perfect winter camouflage.  Like owls and foxes, weasels also rely on rodents for their winter diet, but they use their incredible sense of smell to find their prey in tunnels underneath the snow.

Overwintering insects

We often don’t think about them, but many kinds of insects are also able to survive Pennsylvania winter in their egg or larval stage, and some even undergo incredible transformations once spring returns.

The Cercropia moth, a member of the silkworm family, spends the summer as a large, fat green caterpillar.  In the fall it prepare its overwintering shelter by spinning a tough brown cocoon often resembling a dead, brown leaf hanging from a branch.  There, it spends the winter as a pupa, ready to emerge in the spring as an adult moth.

The familiar wooly bear caterpillar is another winter survivor.  Their black and brown furry coat is not about staying warm, but rather it allows their bodies to freeze in a controlled way.  Woolly bears can survive can temperatures as low as -90°F, usually burrowed down beneath the leaves and snow of the forest floor. They reemerge in the spring to complete their transformation into Isabella Tiger moths.

The snow flea, while not actually an insect, but a small, black arthropod, are quite active and easily observable and quite active during warmer period of the winter.  Springtails, as they are also called, can jump surprising distances because a curled, tail-like structure called a furcula.  We see them on the top of the snow as they emerge from dormancy in search of organic matter in the soil to munch on.

Under the leaves and in the water

Pennsylvania frogs, fish and turtles have unique adaptations that help them to get through the winter months. Wood frogs go into deep hibernation - they stop breathing and their hearts stop beating. Their bodies produce a special antifreeze substance called glycerol that prevents ice from freezing within their cells, which would be deadly. Ice does form, however, in the spaces between the cells. When the weather warms, the frogs thaw and begin feeding and mating again.  With this adaptation, wood frogs typically hibernate above the frost line.

Fish, on the other head deeper into their habitat in search of warmth.  Once ice forms over the ponds and lakes where they live, temperatures in the water underneath the ice remains above freezing.  There is less food and oxygen available to them and they cope by slowing down their activities.   On a bright sunny day, you can spot them through clear ice.

The trail heads at the Andrew J. Conner Nature center and Brown’s Farm will lead you through a variety of habitats, perfect for winter exploration.