Bats. Thought threatening by some people, our bats, rather than fearsome creatures, are harmless minders of nature and keepers of its balance. Bats, like bees and their cousins are pollinators, not only helping to produce our fruit and decorative flowers, but at the same time devouring millions of insects that might otherwise torment humans or damage fragile, economically important crops. And like other animals such as birds, squirrels, mice, and chipmunks they transport plant seeds as they search for food, ensuring continued plant diversity.
The problem now is they’re dying off, by the millions.
The cause, White-nose Syndrome (WNS), was discovered and photographed in a New York cave in 2006 where hibernating bats were observed with unnatural white noses. It was further documented and named the following year by biologists from the New York State Department of Environmental Conservation (NYSDEC) who witnessed erratic bat behaviors and hundreds of dead bats in scattered bats across the state. The U.S. Fish and Wildlife Service reported that “more than a million hibernating bats have died since then, making WNS the worst wildlife health crisis in memory.” The disease plagues multiple species of bats in caves and mines in sixteen states and four Canadian provinces with lethality of near 100 percent in hibernating bat populations.
Although the actual cause of death in these bats is not understood, the Fish and Wildlife Service describes the white muzzle growth as a newly discovered cold-loving fungus, Geomyces destructans. In lab experiments, 100 percent of bats exposed to G. destructans developed WNS. The spores of the fungus are apparently spread bat-to-bat, but like many pathogens may have other paths of infection.
G. destructans is undoubtedly the culprit, but where did it come from and why now? Some species of bats in Europe are known to display white noses, but show none of the symptoms of the disease. A paper published in the journal Emerging Infectious Diseases uncovered data showing that the white-nose growth in European bats was caused by G. destructans infection. The authors of the article proposed that the fungus had probably originated in Europe but did not kill the bats because the flying mammals and the fungus had evolved together, with the bats eventually developing immunity to the attacking fungus. North American bats evolved in the absence of G. destructans and so had no such immunity when it attacked.
The question the paper does not attempt to answer, or even propose a theoretical model for, is how the fungus or its spores were introduced to a new continent and how it managed to find its way into the depths of North American mines and caves. The transport mechanism is still unknown, and may never be understood. It seems though another invasive species has found a new home with no natural controls to keep the fungus in check.
Why be concerned about the bats? Why spend the time and research dollars? The bat’s insect-killing potential replaces tons of insecticides that would be needed to protect crops and eliminate swarms of biting mosquitoes. The same mechanism that allowed the fungus to gain a deadly foothold in the caves could someday be responsible for the introduction of an invasive species that attacks farm stocks, fish farms, agricultural products, or perhaps even humans.
Thriving bat populations are another indication of a healthy environment. Millions of dead bats tell us that something is very wrong.
My book The Double-Crested Cormorant: Symbol of Ecological Conflict is now available in a trade hardcover version at Amazon.com, Barnes and Noble.com, and the University of Michigan Press, which also offers an E-book edition. Also, check your local booksellers for availability.
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