One of our volunteer naturalists recently shared a story of an exciting discovery she made at her bird feeders. She loves to tell anecdotes about the slew of birds that frequent her backyard feeders during the day. However, this time her visitors were not birds, and they appeared in the middle of night. She had seen odd things at night when passing by the windows that looked out towards her yard: a bird feeder swinging wildly with no wind and shadows cast by the moonlight that moved in a herky-jerky scuttle up nearby trees. It wasn’t until one night this winter, with the flick of a light switch, that she caught these mysterious critters in action:Frozen in the glare of a flood light, a dozen southern flying squirrels (Glaucomys volans) perched on her bird feeder, gorging themselves on sunflower seeds. The bulk of a flying squirrel’s diet consists of seeds, nuts and fruits; although, they won’t turn their nose up at insects, bird eggs or even the occasional animal carcass if they happen upon it. Because these nimble woodland mammals are strictly nocturnal and spend most of their time 20-30 feet up in the trees, flying squirrels are rarely seen. Most people are only lucky enough to experience flying squirrels by hearing bursts of their high-pitched “tseet” calls in the darkened woods. In addition to these audible calls, other sounds made by flying squirrels are ultrasonic and may function as a type of echolocation, guiding the squirrels towards good landing spots. Although rarely seen, these small gliding animals are found in most oak-hickory woodlands throughout Lake County, Illinois.
A southern flying squirrel is similar in size to an eastern chipmunk, and most school children will correctly tell you that a flying squirrel does not actually “fly.” Rather, it uses the layers of loose skin along each side of its body to glide through the treetops. They typically glide at a downward angle of 30-50 degrees for a distance of 20-30 feet (although, the farthest distance recorded is 150 feet!). When gliding, these squirrels can maneuver in the air, twisting and turning in 90-degree angles to avoid branches and avian predators, such as owls. Southern flying squirrels also have extremely large eyes that aid their vision in low light and tiny whiskers called “vibrissae” on their cheeks, chin and ankles to help them navigate at night.
Southern flying squirrels have two breeding seasons, the first of which falls in February and March here in Lake County, Illinois. This time of year is a good time for observing flying squirrels. In addition to their courtship displays, these gregarious critters tend to congregate in groups of up to 20 squirrels in a single cavity (often an old woodpecker nest) for warmth at the end of winter. Watch your bird feeder and you may get lucky with midnight visitors in your own backyard. The best way to hear and possibly glimpse flying squirrels in the Lake County Forest Preserves is to visit in the evening. While most of our trails close at sunset, two solar-lighted trails stay open until 9:00 pm daily through March 30th, 2013.