One late winter day a few years ago I noticed something different about a small bird house I had hanging in a tree. There was new nest material protruding from the entry hole and rodent chew marks around the opening. I had cleaned out the old nest made of sticks and twigs that a house wren had left the pervious summer and wondered what species might have constructed a new nest during the colder months. Surely not a bird.
The bird house was high enough that I could just reach it. Because I thought I knew what was inside, I got my camera ready, reached up, and gently knocked on the box. A little grey head with huge black eyes popped out, followed by a soft, furry body with dramatic extra skin between the front and hind legs. It was a southern flying squirrel (Glaucomys volans)! I just managed to get a couple of photos before it ran back inside the box.
Flying squirrels live in deciduous forests in the eastern United States from southeast Canada to Florida. Because they are exclusively nocturnal and secretive, they are seldom seen. In fact, most people are surprised to learn that they are common in the Barrington area. Rare encounters occur when they occasionally find their way into our houses, or when we investigate unusual bird-like squeaking after dark and find them visiting bird feeders next to the house. I once found a flying squirrel inside our house several decades ago. It likely had come down the chimney; I caught it in a towel and released it outside. The one in the nest box mentioned above was only the second flying squirrel I saw locally after over 30 years of living here. I now have motion-activated, infrared, video trailcams in the woods around the house to document our local wildlife, and I was surprised how frequently flying squirrels are caught on camera. They are especially active in the fall when they are gathering hickory nuts and acorns, but they also drink from a pond I installed in the woods as a water source for wildlife. My trailcams have recorded other animals at night when suddenly a flying squirrel went gliding by above them.
Flying squirrels are related to but smaller than the common eastern gray squirrels (Sciurus carolinensis) and fox squirrels (Sciurus niger) that live in our area. They are closer to the size of an Eastern Chipmunk (Tamias striatus): some 8 to 9 inches long and 2 to 3 ounces in weight. Their fur is soft and gray and, being nocturnal, their eyes are very large and black. Of course, flying squirrels are best known for their patagium, the folds of skin that stretch between front and hind legs to create a parachute-like membrane. When they take off from a high perch, they extend their legs in an “X” shape, pulling the skin membranes taught and allowing them to glide through the air. “Flights” usually last 20 to 30 feet but can go as far as 200 feet. They descend at a 30 to 40-degree angle and are so agile that they can turn up to 90-degrees to miss obstacles, avoid hunting owls, and land on their target.
Flying squirrels are cavity nesters and need old trees with crevices or woodpecker holes for their nests. As I found out, they also use bird houses. They don’t hibernate but are less active in winter than summer. To tolerate cold weather, they slow their metabolism, lower their body temperature, and gather in communal nests to share body heat.
Just a few years ago Jon Martin, a biologist in Wisconsin, was shining an ultraviolet light in the forest at night, looking for fluorescent lichens and fungi. He heard the chirping of a flying squirrel, shined his light on it, and was amazed to see it glow pink in the UV light. Further research looking at museum specimens showed that all three species of North American flying squirrels fluoresce pink under ultraviolet light, and all are brighter pink underneath than on top. Other species of squirrels did not glow.
It is unknown why flying squirrels fluoresce, but it probably relates to being nocturnal. Low light conditions are rich in UV light, and many nocturnal animals can see some types of UV light. The fluorescence might be used in communication with other flying squirrels. It might signal health and fitness to potential mates. Because many lichens and fungi fluoresce, it might provide camouflage at night. Some owls have pink fluorescence on their undersides, so it might be a form of mimicry to avoid predation. Flying Squirrel fluorescence is a relatively new discovery and many unanswered questions remain.
About the Author
Stephen Barten is a retired small and exotic animal veterinarian, naturalist, award-winning wildlife photographer, avid birder and herper (reptiles), and bluebird and bumblebee monitor living in Tower Lakes, Illinois.
A long-time Citizens for Conservation volunteer, Steve loves observing animals in their native habitat. He has traveled around the world to observe and photograph wildlife, but always is pulled back to the beauty and variety of birds and wildlife in the Barrington area and his own back yard. He hopes his images inspire others to appreciate and conserve the beauty of wildlife.