In 2013, I got to participate in a bat census at the American Museum of Natural History’s Southwestern Research Station, a biological hotspot with more kinds of bats than anywhere else in the US.
I discovered fruit bats smell like a slice of fresh pineapple, and have delightful upturned noses speckled with pollen. Insect-eating bats.... smell a bit like a cat litter-box. But they are still fluffy and cute, like flying leathery hamsters.
Trying to convince people they should love bats (and that bats aren't rodents) is not easy. When I recounted my amazing bat experience was to friends, inevitably they described their fear of bats and how best to kill said bats with blunt instruments. So, pretty much the same conversations I have with everyone about spiders.
The argument I make in favor of spiders and bats is also the same; both are economically and ecologically important. Bats provide pest control services estimated at a value of $22.9 Billion dollars per year in the US by eating bugs that are agricultural pests, as well as mosquitoes. Some bats are pollinators; thank a humble bat for your tequila.
We need bats; but our bats are dying. In Spring 2006, 6.5 million Little Brown Bats (Myotis lucifugus) lived in the Eastern US, making them America’s most common wild mammal species. Later that same year, thousands of little bodies were discovered strewn outside caves near New Albany, New York. Bats were dying in catastrophic numbers.
Eight years later, millions of bats have died, and still continue to die. Little Brown Bats are now listed as a "threatened species" in multiple states. This is “the most precipitous decline of North American wildlife in recorded history.” And yet, public outcry over the loss of bats has been strangely muted.
What's killing the bats isn't pesticides, viruses, or bacteria. It's a fungus, Pseudogymnoascus (Geomyces) destructans, and it causes a disease called White Nose Syndrome. There is no treatment or cure.
I asked one of the bat scientists participating in the Southwestern Research Station bat census what would happen if White Nose Syndrome showed up in Arizona, a key migratory corridor for bats traveling to Central America.
“Oh God,” he said. There was a long silence. “It would be the end of the world.”
White Nose Syndrome infects the skin of bat faces, wings, and ears, and then invades and breaks down underlying skin and connective tissues. Infected bats starve as their hibernation is disrupted, dehydrate as their fragile wings tear, and die.
The fungus that causes White Nose Syndrome is believed to have been accidentally transported to the US on a caver's shoes. Like other diseases imported to the "New World" from Europe, White Nose causes catastrophic mortality in indigenous populations. Unlike Eastern European bats, which tolerate the infection, North American bats do not seem to have any resistance to this fungal disease. White Nose mortality rates are 90-100 percent in American bat caves.
WNS fungi reproduce by making highly resistant spores. Those spores happily live in damp, dark, cool caves – the primary places colony-nesting bats roost for the winter and breed – for decades. Even if we bred bats in captivity and released them, they'd be reinfected as soon as they entered a cave.
Alas, breeding bats in captivity doesn't seem to be an option; there was less than a 25 percent survival rate in one attempt to bring an endangered bat species into captivity. Research papers have started to calculate odds of extinction; one suggests Little Brown Bats have a 99 percent chance of extinction by 2026, even in a best case scenario.
Scientists have asked that USFW list the species as federally endangered. On the East coast, work has shifted to "survivor studies;” monitors are looking to see if any bats haven’t died. When a good outcome is “not everything is dead,” you know things are dire.
Eleven North American cave-hibernating bat species are known to be infected with White Nose, including some that were already listed as endangered species. A 2014 publication estimated the total biomass of insects no longer being eaten as a result of catastrophic loss of multiple bat species is 2,079 metric tons of insects per year.
This period has been especially difficult for bat biologists. Animals they spent decades trying to save (and years trying to convince the public they should like) litter the ground of caves. The floors of breeding colonies are bone houses.
The last eight years have been a desperate race to get out ahead of the fungus. There are two ways to do this: Finding contaminated caves and closing off access; and finding clean caves and preventing infections through biosecurity measures, mostly aimed at preventing humans from bringing in fungal spores on their shoes. The hope is that by closing infected caves, the spread of the disease can be slowed while lab scientists work to find a solution.
It's not going very well. The map below documents the disease's steady spread from the initial 2006 discovery in New York.
Once a bat looks white and fuzzy, it’s going to die. In order to know if a cave is infected, biologists need to make a WNS diagnosis in bats before they get to that stage. To diagnose a bat when WNS was first discovered, they had to euthanize it and then send the whole animal to a lab for a battery of genetic tests and fungal cultures. Cynthia M. Sandeno, Forest Service National Cave and Karst Coordinator, said "It's been horrible.... We love bats. To have to go into a cave and kill a bat, even as humanely as possible, it's just awful. Heartbreaking."
Helping Bats Hang On
One small bit of good news: diagnosing bats with White Nose just got a little easier. Under UV light, infected bats light up with an orange-yellow light. UV light is used in humans to check for skin fungal infections as well; ringworm and dermal candidiasis both light up, and are a key diagnostic tool.
The fluorescence corresponds closely to the presence of skin lesions caused by WNS. The UV light can be used to locate an area for a small punch biopsy that leaves the bat healthy and able to fly again. So now identification and screening for the disease is faster and easier on both scientists and bats. "The UV technology has been wonderful...so much less intrusive," said Sandino.
In June 2014 the Forest Service issued a 5-year closure on caves in 12 states to try to slow the spread of White Nose Syndrome until a viable treatment can be found. Early reports this year suggest in some areas fewer bats are getting infected and dying. Whether this is because the bats are becoming resistant, or the fungus is evolving to be less toxic, is the focus of continuing research and monitoring.
Sandino remains upbeat: “The cure will come from a researcher in a lab; but protecting the remaining bats is something everyone can participate in. We have to remain hopeful. We just have to.”
Here's a video showing how biosecurity measures are being implemented to protect bats in our National Parks and Forests.
What Can You Do?
- Stay out of caves and mines where bats are hibernating during winter.
- Reduce disturbance to natural bat habitats around your home (e.g., reduce outdoor lighting, minimize tree clearing, protect streams and wetlands).
- Honor cave closures. Check with your state and federal agencies or a local chapter of the National Speleological Society for the status of caves and caving in your area. Follow National WNS Decontamination Protocol to clean and disinfect clothes, footwear, and equipment used in caves or mines.
- Help spread the word about the value of bats! Bats are good neighbors, not pests.
- Recognize that rabies in bats is extremely rare.
2014 References:
Gregory G. Turner, et al. 2014. Nonlethal Screening of Bat-Wing Skin With the Use of Ultraviolet Fluorescence to Detect Lesions Indicative of White-Nose Syndrome. Journal of Wildlife Diseases; 140522114529005 DOI: 10.7589/2014-03-058
Jachowski, D.S., C.M.B. Jachowski, and W.M. Ford. 2014. Is white-nose syndrome causing insectivory release and altering ecosystem function in eastern North America? Bat Research News, 55(2): 21–24.
Zukal J, Bandouchova H, Bartonicka T, Berkova H, Brack V, et al. (2014) White-Nose Syndrome Fungus: A Generalist Pathogen of Hibernating Bats. PLoS ONE 9(5): e97224. doi:10.1371/journal.pone.0097224
