There are more than 1,200 species of bats in the world. That's more than one-fifth of all mammals! They range from giant flying foxes with two meter wingspans to itty-bitty bumblebee bats that weigh less than a penny.

They live just about everywhere, except for the poles and the harshest of deserts, and they've been around since the dinosaurs. But here in North America, bats are in mortal danger, and the poor little guys can't even activate their own Bat-Signal to call for help! A terrible infection is ravaging their populations, and it's as serious as a heart attack.

[Intro plays]

White nose syndrome, or WNS, is a deadly disease that affects hibernating bats. It first appeared in 2006 in New York state, and has since spread like the sinister blossoming of a zombie outbreak, expand south and west at an alarming rate. The disease has been detected in 22 states and in five Canadian provinces so far, killing an estimated 6.7 million bats along the way. It's been called the most precipitous wildlife decline in the past century, in North America.

The disease is named for Geomyces destructans, the powdery, white cold-loving fungus that infects the ears, muzzles, and wings of hibernating bats. Recent genetic tests indicate that the fungus was introduced from Europe, though the bats over there are unaffected by it. Bats don't fly across the ocean, so it's thought that humans, probably cavers, accidentally transplanted the fungus on contaminated clothing or gear.

The funk attacks in winter while bats are vulnerable in hibernation, eventually triggered in a crazed immune response, where their bodies attack health tissues and fungus alike. It also drives bats to abnormal behavior, like flying around during the daytime in winter, when they should be snugly tucked away in their bat caves. This causes the animals to burn through their fat reserves, until they become too weak, emaciated, or hypothermic to survive.

Because bats are communal roosters, the fungus spreads at alarming rate. WNS has been detected in at least eleven bat species, four of which are endangered, and five of which have experienced mortality rates as high as 95% in infected caves. Little brown bats, in particular, have been hit hard. That's a species name, I'm not just saying that they're little and brown.

Wildlife agencies estimate the northeastern bat populations have declined 80% in the last 5-6 years, and as the disease spreads, many worry that some species will be regionally extinct within the next 20 years. So far, there's no cure. Bats are long-lived and reproduce slowly, typically only having one pup a year. So even if the fungus doesn't wipe them all out immediately, a quick recovery is very unlikely.

And the ecological consequences of such massive die-offs will have far-reaching effects. I mean, some of these guys eat their weight in insects every night, like, a thousand mosquitoes every hour. That's a lot of mosquitoes, people! And they do all that insect control for free! They're also vital pollinators and seed dispersers for tons of plants, and their poop, or guano, is a valuable fertilizer.

Because the disease hit so hard and fast, and is so totally deadly, bats haven't had much of a chance to develop an immunity, but a new study is showing that they may be starting to change their behavior. Little brown bats are consummate cuddlers, they typically cluster together during hibernation, easily spreading infections, but since so many of their friends have died, the surviving bats have begun to hang further apart, roosting individually, and that small buffer may be a lifesaver.

If you're as worried about the bats as I am, the non-profit Bat Conservation International says there are a few ways you can help. One, report any weird, late-winter bat behavior to your local wildlife agency. Two, check the U.S. Fish and Wildlife Service's list of cave closures, and don't try sneaking in where you shouldn't be sneaking in, not that I figure you would. Three, don't explore caves in infected states and then traipse across state lines to unaffected state caves. Four, if you just love to spelunk, it is super-important to follow decontamination guidelines. Hose your gear and clothing down with Lysol or bleach solution, or some other approved treatments upon leaving a cave. And five, you can also encourage state and federal legislators to put more funding toward white nose syndrome research.

To this list, I would add: if you find a bat that has come down your chimney, or slipped in from the chimney, please don't smack it with a tennis racket. Safely remove it and release the animal with the ardent hope that it will live long and prosper.