Our native bat populations are in great peril. Little brown bats (Myotis lucifugus) have been hit the hardest. They used to be the Northeast’s most numerous bat species. Eastern small-footed myotis and eastern pipistrelles have also been stricken; big brown bats to a lesser extent. The Indiana myotis, which was already in trouble and is protected under the Endangered Species Act, may now become extinct.
A little brown bat with White Nose Syndrome, photographed in Greeley Mine, Vermont, March 26, 2009 (USFWS photo)
Scientists suspect that a fungus is impacting bat populations. White-nose syndrome (Geomyces destructans) thrives in cold humid environs. It attacks bats hibernating in caves (called "hibernacula") where generations have resided for decades and in some cases possibly hundreds of years.
The fungus is believed to have originated in Europe. It penetrates deep into the skin, manifesting on the snout and ears, but is most damaging to the animals' wings. The fungal disorder disorients infected bats. They awaken too early from hibernation, and venture from protective cover in search of food. Since food is unavailable in the wintertime, they starve and succumb to freezing temperatures.
The malady appears to be spreading. The problem has been recorded into eastern provinces of Canada, as far south as Tennessee and is now found in West Virginia.
In some caves, as many as 75% of inhabitants are dead. Some reports cite that in other hibernacula, 90% to 100% of inhabitants have succumbed. Since little brown bats span North America, it is hoped that they would not be wiped out in everywhere. However, to date, northeastern bats are the most seriously impacted by this tragedy that has struck suddenly and spreads quickly. Science News reports that "45% of the little brown bat population continues to die each winter." At that rate, our regional Myotis lucifugus would become non-existent in northeastern North America within 16 years.
The contagion is communicable from bat to bat. It may also be transmitted from bat to cave to bat. It is not known if the fungus is directly responsible for deaths or if it is the catalyst for disorientation, emaciation and immune suppression that presages untimely demise. But it is safe to say that if the bats were not infected they would not be dying in such alarming numbers.
What conditions precipitate infection? We do not know.
- David Blehart, a microbiologist employed by the U.S. Geological survey, conjectured that ingested contaminants might be the culprit.
- Blehart has also theorized that pesticide use may have reduced the numbers of insects upon which bats feast. This cheats bats of the food they require to fatten-up before hibernation; which, in turn, weakens immune response and increases susceptibility to the fungus. I humbly postulate that pesticide infused insects, still flying, which are eaten by bats may also be a contributing factor.
- Dr. Blehart has also speculated that bats that would normally sleep through the winter awaken frequently due to irritation caused by the infection. When repeatedly aroused, infected bats use up the necessary winter padding of fat in their bodies. The result is emaciation, hunger and premature emergence from hibernation.
- A new theory suggests that dehydration from water loss caused by the infection in the bats' wings arouses these mammals to precocious consciousness. In this hypothesis it is the thirst for water which causes early emergence from hibernacula.
But again, no one knows with certainty. It is entirely possible that any combination of the interrelated conditions might work together to produce a perfect, deadly storm.
You may query, "So what! Who cares about bats?" Consider this: bats eat flying insects and lots of them. Bats reduce populations of marauding insect pests which fly at dusk using finely tuned sonar. A single voracious bat ingests as many as 1,000 mosquitoes in a single hour! An up-tick in mosquito-borne illnesses is inevitable if this tenacious menace is are not kept in check. Indeed, the number of individuals contracting mosquito-borne illnesses in the northeast is on the rise.
Increased pesticide use may kill insect pests, but could also inadvertently contribute to and foster even more bat deaths as well as deaths of so many beneficial bees needed to pollinate fruits and vegetables. Unnecessary pesticide use in general can degrade living soil structure and can poison well water.
At Quackin' Grass Nursery, we used to have a vibrant bat population. They live in the spaces under boards where the outer walls meet the roof line of our gambrel-style barn. We are delighted but saddened to still see just a few, flying and flitting in silhouette against dusky skies. It is a far cry from one memorable warm evening when I ventured outdoors. To my amazement, there were easily 100 or more individuals flying in a large circular rotation 10 to 20 feet above the ground. I think I might have happened upon a mating ritual. I expect that some descendants we presently see came from that lusty evening. May our bats survive and prosper.