First it was deformed frogs. Then it was bees, dying of a mysterious illness called Colony Collapse Disorder. Now, reports from environmental scientists warn of the deaths of thousands of bats along the east coast of the United States, in a plague researchers are dubbing ‘white-nose fungus'.

Early in 2007, residents near Albany, New York observed bats flying in daytime, in some of the coldest weather of the year. Since bats normally fly at night, and hibernate in caves over winter, Alan Hicks of the New York State Department of Environmental Conservation, in cooperation with the U.S. Geological Survey - which monitors caves and bat populations as part of its geophysical mandate - made a disturbing discovery.

Ninety-seven percent of bat populations, from New York, Connecticut, Maine and Vermont, had been decimated, presumably by a disease which left the dead and dying with a powdery, white substance around their noses, ears and wings.

Researchers have finally identified the fungus, or mold, and reported their findings in the online journal Science. It appears to be a psychrophilic (or cold-adapted) fungus related to Geomyces, but with a distinctly different morphology. Geomyces are present in soil throughout the world from temperate to Antarctic regions, thrive between 41 and 50 degrees Fahrenheit, reproduce at 39 degrees Fahrenheit, and are the predominant organisms associated with polyester polyurethanes buried in landfills.

The problem, at least from a scientific point of view, is that fungi don't normally kill otherwise healthy animals, so David Blehert (the lead author of the study) speculates the fungus may cause skin irritation, waking the bats more frequently during hibernation and causing them to use up their fat reserves before spring. Since the fungus thrives at the same temperature as bat caves (39 degrees) and hibernating bats, its spread is almost assured. Blehert bases his assumptions on the fact that many of the dead bats were also emaciated, and many were found outside caves, as though searching for food.

Blehert, the head of diagnostic microbiology at the U.S. Geological Survey's National Wildlife Health Center in Madison, Wisconsin, speculates that either a person or an animal may have carried the first specimen of Geomyces into Howes Cave in upper New York State, where the epidemic was first noted in 2006.

By 2007, the disease had spread to a 10-mile radius. By 2008, it covered more than a 130-mile radius. The fungus has affected small and large brown bats, northern bats, tricolored bats, Indiana bats and small-footed Myotis. Blehert now estimates losses upwards of 200,000. 

In spite of the knowledge they have acquired regarding Geomyces, scientists are still puzzled by several anomalies. First, fungi are opportunistic parasites, which live on and spread via their victims but don't usually kill them, as this would be counterproductive. Second, the fungus Geomyces is not sufficiently pathogenic on its own to account for such high rates of mortality in bat populations. This has led some to speculate that the fungal infection is a side-effect of some other illness or disturbance, which may be as simple as a reduction in the amount of insects bats feed upon, or as complex as an unidentified environmental toxin.

Thomas Kunz, of Boston University's Center for Ecology and Conservation Biology, has been studying bats for 40 years and says the mortality rate is ‘unprecedented'. Kunz and his team have developed a tripartite approach to the mystery. By studying the body weights of hibernating bats in different areas, and then determining the amounts of stored fatty acids obtained by eating insects, and finally determining if the deaths are a result of failed immune systems, Kunz and colleagues hope to establish the real cause.

If hibernating bats are too thin, they're not getting enough to eat before beginning hibernation. If the weight is adequate, but not composed of the unsaturated fatty acids derived from eating insects, the problem may point back to insect populations being reduced by insecticides. Kunz is careful to note that his team has not identified a ‘smoking gun', but feels certain that diligent research will produce one.

Blehert is less optimistic, and compares white nose syndrome to a lethal fungal skin infection called chytridiomycosis which has wiped out much of the amphibian population during the past 30 years.

Bats are an integral part of the natural world, helping to keep down insect populations. A bat can eat from 25 to 50 percent of its own body weight in a single night. Bats each such pests as corn borers, cucumber beetles and moths. Bats also pollinate flowering crops like bananas, mangoes, dates and cactus, which often flower after the sun goes down. Fruit-eating bats swallow and then excrete seeds, replenishing tropical rainforests.

Bats, much maligned in folklore, recently won 4^th place in the Zoological Society of London's invaluable species list. As the Society notes, bats are also the ‘canaries in the coal mine' of earth's ecological health, and declining populations - for whatever reason - are a warning of irreversible damage to the biosphere.

White nose syndrome is so far confined to the Northeast United States. Should it spread, the most effective insect eradicator ever invented - and the most ecologically friendly - will go the way of the dinosaurs, leaving mankind increasingly dependent on toxic insecticides, which are likely the source of the problem in the first place, though only time will tell.

Hopefully a cause and cure will be found before bats enter the long list of species lost during this, the Sixth Great Extinction.

Further Reading:

• The Bats and the Bees
• Trouble in the Bat Cave