Little brown bats with white-nose syndrome, New York Credit: Nancy Heaslip, New York Department of Environmental Conservation

What is killing our bats?

The Problem and Effects:
White-nose syndrome (WNS) is a disease affecting hibernating bats. Named for the white fungus, Geomyces destructans, that appears on the muzzle and other body parts of hibernating bats, WNS is associated with extensive mortality of bats in eastern North America. First documented in New York in the winter of 2006-2007, WNS has spread rapidly across the eastern United States and Canada, and the fungus that causes WNS has been detected as far west as Oklahoma.

Bats with WNS exhibit uncharacteristic behavior during cold winter months, including flying outside in the day and clustering near the entrances of hibernacula. Bats have been found sick and dying in unprecedented numbers in and around caves and mines. WNS has killed more than 5.7 to 6.7 million bats in eastern North America. In some hibernacula, 90 to 100 percent of bats have died.

What We're Doing:
Fungal infections do not typically result in death, so the U.S. Fish and Wildlife Service has been evaluating whether environmental contaminants interfere with hibernation, metabolism or immune function. A disruption of these processes may increase sensitivity to the fungus associated with WNS and worsen the effects of the disease.

Environmental contaminants, particularly a class of pesticides known as organochlorines, have been implicated in bat mortality events historically. Bats may be more susceptible to the effects of contaminants than other mammals due to their high metabolic rates and annual hibernation cycles that require significant fat deposition.

Rapid depletion of fat reserves may mobilize fat soluble contaminants into the bat's blood stream. Classes of pesticides currently being used may adversely affect bat populations by interfering with metabolic, neurologic, or immune functions. Emerging contaminants, such as detergents, discarded medicines and plasticizers are also of increasing concern in the environment due to their widespread use.

The Service has evaluated contaminant concentrations in dead bats collected from New York, Massachusetts, Pennsylvania, Vermont and New Hampshire. Though a complete report is not yet available, our investigation has revealed fairly low concentrations of organic contaminants, including as polychlorinated biphenyls (PCBs) and pesticides, such as DDT. Mercury and chemicals, such as polybrominated diphenyl ethers (used as flame retardants), are present in most bat samples. Additional analysis is ongoing for emerging contaminants.

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