In the past eight years, a devastating fungal disease called “White Nose Syndrome” has decimated nearly 7 million bats in the eastern United States. Cases of White Nose Syndrome have now been discovered in Michigan and Wisconsin, bringing the total numbered of plagued states to 25. It has also been identified in five Canadian provinces.
“We’re observing the most precipitous decline of a group of species in recorded history, and it’s happening right here in our region,” Vermont biologist Scott Darling said in a statement earlier this year. “Several species, such as northern long-eared bats, have virtually disappeared in less than a decade, and we are getting increasingly skeptical that they will ever be able to rebound.”
Given that one average-sized bat can eat 1,000 insects per hour, the loss of millions of bats continues to be an ecological and economic disaster.
A 2011 study found that bats save the U.S. economy between $3.7 billion and $53 billion each year by preying on agricultural pests and disease carriers like mosquitoes.
The first documented case of White Nose Syndrome was recorded in February 2006 by a recreational caver who was exploring Howes Cave in New York. He photographed a bat with an unusual white growth on its muzzle. At the same time, American beekeeper David Hackenberg began observing another phenomenon — vanishing bees.
Batting Around Facts on White Nose Syndrome
Swaths of U.S. caves now have disinfection mats or are simply closed to the public. Every cave and mine in the U.S. Forest Service’s Southern Region, for example, will remain closed until 2019.
Since bats have naturally depressed immune responses during hibernation, any pathogen can become extremely destructive at certain times of year. But is the identified pathogen, the fungus Pseudogymnoascus destructans, which was unknown prior to the discovery of White Nose Syndrome, the root cause of this fatal syndrome?
Researchers have been unable to determine if White Nose Syndrome emerged because of the introduction of a new fungus or because the fungus was already present and the bats became increasingly susceptible, due to a systemic weakening of their immune systems from exposure to toxic contaminants.
Scientists have already found evidence of several similar toxin exposure-related susceptibilities in other species: Exposure to PCBs has been correlated with higher levels of roundworm infection in Arctic seagulls; the popular herbicide atrazine has been shown to make tadpoles more susceptible to parasitic worms; consumption of pesticide-contaminated herring has been found to impair the immune function of captive seals; and systemic neonicotinoids in commercial agriculture are now widely linked to Colony Collapse Disorder and the plight of the honeybee.
Could a similar phenomenon be to blame for White Nose Syndrome? Studies have shown that both diseased and non-diseased bats have DDT, PCBs, and mercury in their fat tissue. But more studies must be conducted to understand how toxins might play a role.
Bats are especially vulnerable to chemical pollution. They’re small — the little brown bat weighs just 8 grams — and they can live up to three decades.
“That’s lots of time to accumulate pesticides and contaminants,” points out Marianne Moore, bat researcher and post-Ph.D. and doctoral associate at New York State University at Stony Brook. Moore has been studying the immune responses of White Nose Syndrome bats since 2008 and the immune systems of bats in relation to rabies ecology, mercury exposure, and stress physiology since 2005.
Not only is White Nose Syndrome harming endangered species like the Indiana bat; it may soon force a previously stable species, the northern long-eared bat, to join the U.S. endangered list. Rebounding from a loss is difficult because females only give birth to one pup per year.
Contact the Bat Conservation Organization for more information.
Maryam Henein is an investigative journalist, professional researcher, and producer of the award-winning documentary Vanishing of the Bees.
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