Fantastic Flying Squirrels
As a bat biologist, I am often quick to point out the fact that bats are the only true flying mammal and that “flying” squirrels merely fall with grace. While it is correct to state that flying squirrels cannot truly fly, they are more than graceful fallers that let gravity do their work for them. They are fascinating, adorable creatures and warrant a closer look. Flying squirrels, as well as flying lemurs and other gliding mammals, glide through the use of a parachute-like membrane that connects their wrists and ankles. This membrane can stretch out when extended and catches air when a flying squirrel jumps off a tree or branch. A flying squirrel’s legs act as a steering wheel, and the tail acts as a brake. Using this method, they can accurately glide from tree to tree, spanning a distance of as much as 150 feet in a single glide!
Until recent DNA analysis indicated otherwise, there were only two distinct flying squirrel species in North America that had been described by science – the northern (Glaucomys sabrinus) and southern (Glaucomys volans) flying squirrel. In the last year, a new species has been identified in the Pacific Northwest. It has been named the Humboldt’s flying squirrel (Glaucomys oregonensis) in honor of Alexander von Humboldt, a well renowned naturalist of the 19th century. This newly identified species means there are now 45 different species of flying squirrel on the planet, with numerous subspecies mixed in there as well.
Here in Chautauqua County, we are lucky to be at the southern boundary of the northern flying squirrel’s range and well within the southern flying squirrel’s range. This means we have two of the three species found in North America right here in our back yard! The northern and southern species can be differentiated by size. Southern squirrels are noticeably smaller, maxing out at about 10 inches. Northern squirrels can grow to about a foot in size. Finally, the northern species is more brownish in color than their cousins, which is also useful in telling them apart.
Both species prefer similar habitat, living in deciduous and coniferous woodlands. Nut-producing trees like hickory and oak are more likely to harbor southern flying squirrels, while northern squirrels prefer old growth forests or stands of beech/birch/maple/hemlock. Like many tree-dwelling creatures, they utilize dead snags, woodpecker holes, and other cavities that can be found in forests, often living in groups (up to 50 have been found in one nest), although the species never cohabitate in the wild. They are omnivores, meaning they consume both plants and animals. This includes a variety of nuts, berries, fruits, and fungi; as well as insects, eggs, birds, and carrion. They are known to be one of the most carnivorous groups of squirrels and will frequently supplement their diets with meat. While they are agile and quick to escape, they are still prey to various predators such as owls, martens, and hawks.
One difference between our two gliders’ diets is a dependence on nuts and seeds in the southern species (who will store food for the winter) and a heavier diet of fungi and lichen in the northern species (they do not store food for the winter). This heavy diet on fungi has an added ecological impact. The spores of the fungi pass through the digestive tract and become dispersed across the landscape. This is crucial in maintaining healthy forests by propagating nitrogen-fixing bacteria and fungi that form critical relationships with trees. These fungi, called mycorrhiza, are increasingly recognized for their profound importance in assisting plants in absorbing nutrients and water, while excluding harmful fungi that can damage roots. Mycorrhizal fungal relationships are similar to a biological internet, connecting the roots of almost all trees in our woodlands.
While they are rarely seen by us, these fascinating critters often outnumber the more commonly seen tree and ground squirrels. This is due to their nocturnal habits and wooded habitats that put them out of sight for most of us. Like many of our common species of wildlife, they are understudied and much remains to be discovered about their life history, biology, and ecological relationships. There is evidence of high frequency calls and potential for echolocation-like navigation, similar to what can be found in our bat species. This hasn’t been thoroughly studied, but ultrasonic vocalizations in laboratory and field settings have been documented, which may be used for transferring information. Few mammals aside from bats and cetaceans (whales and dolphins) have been shown to echolocate at any level. How exciting that we may have some squirrels out there in our forests using sonar to glide along their path!! This is likely to just be the tip of the iceberg. Surely there is plenty more to learn about our fantastic flying squirrels!
The Chautauqua Watershed Conservancy is a local not-for-profit organization that is dedicated to preserving and enhancing the water quality, scenic beauty and ecological health of the lakes, streams, wetlands and watersheds of the Chautauqua region. For more information, call 664-2166 or visit www.chautauquawatershed.org or facebook.com/chautauquawatershed.