Less than two years ago, the deaths of bats by White-Nose Syndrome (WNS) was called the number one crisis affecting mammals in the US. Since then, this fungal disease has spread to 22 states and five Canadian provinces, and killed some seven million bats. Little brown bats, once America's most common bat species, have been hard hit, with mortality rates greater than 90% in many affected states, according to the US Fish & Wildlife Service (USFWS).
This shouldn't merely worry bat lovers; despite their rap as creepy bloodsuckers, bats play a multi-billion-dollar role in agriculture. But while the collapse of bee colonies across the US and Europe over the same period has grabbed headlines, the bat story seems to be in hibernation.
"The thing that is alarming to me is the fact that people are not alarmed," says Eileen Choffnes, Scholar & Director at the Forum on Microbial Threats at the Institute of Medicine in DC.
White-Nose Syndrome, named for the white fungus (Geomyces destructans) it leaves on hibernating bats' noses, wings, and bodies, was first discovered in the US in a cave in the state of New York in 2006. The fungus is believed to have come from Europe where so-called Old World bats can be infected without any apparent ill-effects. Introduced into the North American bat population, though, it's proved deadly. The fungus causes the bats to wake during hibernation, possibly expend too much energy, and ultimately starve to death.
The fungus has rapidly spread from New York to caves and mines in other states and Canada, and there's no known cure for the disease. In some cases, 100% of bat populations have been wiped out in infected caves. Of 46 American bat species, says Ann Froschauer of the USFWS, 26 hibernate and so are at risk. The disease "could wipe out half of the bat species in the US," she says. "It's caused one of the fastest declines of wildlife that we've seen in the US."
Bats are crucial to the ecosystem. They eat disease-carrying insects like mosquitoes and feed on crop-damaging caterpillars and worms, contributing an estimated $23 billion (pdf) annually to the agriculture industry in pest control and pollination. They also, like bees, pollinate certain plants; certain species of bat are said to be so interdependent with the agave, the source of tequila, that one might not survive without the other.
Their loss is compounded by the fact that they reproduce slowly, producing only one pup a year, explains Choffnes, and at best five pups in a lifetime--assuming they survive to adulthood. What's worse, hibernating bat species have their pups while in hibernation. It's in these caves and mines that they are most at risk for contracting WNS. And then there are other bat enemies, including pesticides, pollution, wind energy, habitat loss, and various diseases.