The state of bats in Vermont and what you can do to help
By Mary Van Vleck | Contributor
One of the greatest pleasures of Vermont’s all-too-short summer is relaxing outside on a balmy evening when the day’s chores are done: tending the gardens, watching the birds, greeting the neighborhood kids and marveling at the evening sky. Then along come the mosquitoes, destroying our peaceful reverie with their maddening high-pitched whine. That’s when, rather than birds, we wish there were more bats. Bats are the major predator of night-flying insects. The native little brown bat can consume over 1,200 insects an hour and over 3,000 insects per night. Considering that there may be 100 bats in a nearby roost, you can appreciate how important bats are in insect control.
Sadly, bats are one of the most misunderstood and maligned of our native animals. Many people fear them or have cursed and killed them when they get into homes and barns. They worry that bats carry rabies (fewer than 1 percent carry rabies, and if sick with the disease, their tiny bodies succumb within four days). Or that a bat will get stuck in their hair —have you ever heard of that actually happening? Bats are not blind and, in fact, have very good eyesight. However, in the dark they pursue their prey by echolocation rather than sight—they make ultrasonic sounds that echo back, indicating the exact location of their prey.
The best way to encourage a bat’s quick exit is to close all entrances to other parts of the house, turn off all indoor lights and open an outside door or window. Place a light or a lit candle outside and the bat usually makes a beeline for the light.
Bats are the only flying mammals that flap their wings to propel themselves (flying squirrels glide but don’t fly). The fur-covered wings are made of an extremely thin, highly elastic membrane that stretches over the four limbs, enveloping the fingertips and extending to the ankles and tail, which is partially or wholly inside the membrane. The bones of the four fingers are greatly elongated and support the outer half of the wing, providing dexterity and flexibility so that a bat can turn suddenly in pursuit of an insect. Only the thumb, feet and perhaps the tip of the tail extend beyond the wing, which bats use to crawl about and cling to surfaces. And the tail? At least one southern bat—not native in New England—roosts in trees hanging only by its tail.
Nine bat species are native to the northeastern United States, though we are generally familiar with only two—little brown and big brown bats. These two species frequently choose to live in barns or attics where they quickly become a nuisance due to their dark, rice-like droppings (however excellent as garden fertilizer), their squeaks and, eventually, their odor. Little browns seek the protection of a building from May to September only. Only the big brown bats would roost inside a building in the wintertime. Most people are unaware of the seven native, forest-dwelling species living nearby in treetops, tree cavities or under flakes of peeling bark. They leave the trees at night, swoop over the meadows and lakes, eating enormous quantities of insects (up to half their weight each night), and return to their roosts before sunrise, never bothering people.
Because bats are so important as the major predator of night-flying insects, their crashing populations are a huge concern for all natural ecosystems and for our agricultural production. The declines in Vermont and across the nation are primarily due to the highly contagious fungal disease, white-nose syndrome (WNS), which was identified about 12 years ago. According to the Vermont Fish & Wildlife Department, 5.7 million bats have died off in the northeastern U.S. since 2006 as a result of WNS. In contrast to earlier times, the nighttime skies are empty of bats, and nocturnal insects—including mosquitoes and the moths that produce caterpillars that do such damage to our gardens and agricultural crops—thrive in the absence of their major predator. Sadly, in the absence of bats, farmers must rely more heavily on chemical pesticides.The few bats that have survived fly over meadows and open water, hawking for insects from mid-May through September. As the insects disappear with the advent of colder weather, six of our nine native species leave their summertime roosts for the relative warmth of underground caves and old mine shafts, where they huddle together to keep warm. There they will hibernate until spring, their body temperature dropping to around 60 degrees Fahrenheit. (The three other bat species fly south, one species flying as far as South America.) As the inside of bat caves is warm and humid, and with hundreds of bats snuggled close together, it is easy to imagine how the WNS spread so widely. This has become a very dire situation; scientists worry that we may lose some species altogether, which would be devastating for our ecosystems and agricultural crops.
Scientists are working hard to stop the spread of the fungus, but they have not yet found a cure. Senator Patrick Leahy and other legislators are working to raise funds for bat research. There is reason to hope, as the die-off rate seems to be slowing, perhaps as the surviving bats develop immunity to the fungus.
Mary Van Vleck is a member of the Charlotte Conservation Commission. Contact: firstname.lastname@example.org.
How to attract Vermont bats:
How build a bat box: