Scientists Study White Nose Syndrome Survivors In Vermont Bat Colony

Aug 18, 2015

A muggy summer evening in Vermont, in a swampy area, just as the sun is going down and the mosquitoes are thick in the air might not sound like a good place to hang out. But it's ideal if you're a little brown bat. Or a bat researcher. 

Alyssa Bennett is the small mammals biologist for Vermont Fish and Wildlife. And on this particular muggy and buggy night she is heading up a team of researchers, interns and volunteers to study a population of bats in Addison County. But before getting started, she offers a lesson she's learned the hard way.

"Of all the places I've been," she laughs, "the mosquitoes are worst here. You pull up in your truck and you'd better get in and out pretty quickly, or when you leave that night, you're going to have a truck full of mosquitoes."

Bennett should know. She's part of the Fish and Wildlife team that has spent the last decade studying a colony of little brown bats that take up summer residence in a covered bridge over Otter Creek. It was almost an accident that these bats became study subjects back in 2006.

The bridge was due for some repairs and the Vermont Agency of Transportation was concerned that federally endangered Indiana bats might be roosting in the rafters. So VTRANS asked Fish and Wildlife to conduct a study. "We came out, we set up some nets and trapped bats exiting the bridge and found they weren't Indiana bats, they were little brown bats, which were at the time one of the most common species." But Bennett remembers her supervisor suggesting they put bands on a few of the bats anyway, to see if they could rather informally track them.

A colony of little brown bats use this bridge over the Otter Creek in Addison County as a summer residence. As much as 90 percent of the population of little brown bats in the Northeast has died, but some are surviving.
Credit Jane Lindholm / VPR

"Amazingly, then, White Nose Syndrome hit and we saw these enormous population declines, really devastating," Bennett says. After the fungal illness was found in Vermont bats in 2007, it wiped out massive populations of little brown bats around the state. Today, the entire eastern side of Vermont "pretty much has no little brown bat colonies anymore, and they used to be everywhere; hundreds — thousands of bats in a colony."

Somehow, some of the bats in this colony in Addison County have survived. "We have the longest records that I know of for this species of bats surviving through WNS," says Bennett. Two bats that were originally captured and banded in 2006, before White Nose Syndrome, were found in 2013. As much as 90 percent of the population of little brown bats in the Northeast has died, but some are surviving, and these two bats are proof. Which makes them very valuable to researchers.

So Bennett and her team are out at dusk trying to capture a few more bats to study why they're surviving when so many other bats aren't. "I don't know whether it's something special about this colony or if we have a situation going on where bats, for example, have moved from the eastern side of the state, the only ones that are left and have congregated in these areas. It's a question that everyone's trying to look into."

Bennett and her team set up a couple different kinds of nets to trap the bats as they came out of the bridge and two nearby bat boxes. Pretty quickly after sunset, a few unlucky bats found themselves ensnared in a kind of trap called a harp net. 

Fish and Wildlife staffers set up a harp net to trap bats as they emerge from a bat box at sunset. The adult bat research is geared towards figuring out why these bats have survived White Nose Syndrome.
Credit Jane Lindholm / VPR

The bats fly into the vertical strings of the harp net and slide down into a little plastic trough. Seven bats beat their little wings against the plastic sheeting, making an audible chirping or squeaking sound signaling their displeasure. The researchers hang back, hoping to catch a few more unsuspecting subjects.

Most of the bats here are females and their young. The males don't stay with the babies, so they are able to wander more than the females who stay with their pups. Because they're mammals, they nurse their young. When the pups are first born, they stay in the nesting sites while their mothers go out hunting. But by late July, the pups are flying, or volant, and the whole colony comes out to feed on aquatic and flying insects.

Another type of net, called a mist net, is set up in between some trees in a corridor that the bats often take from the bridge to a nearby field. The net is spread across the opening in the leaves, about 10 feet high. The bats fly into it and get caught.

Sweeping the light from her head lamp across the thin netting, Fish and Wildlife intern Jessica Ralston spots a bat and moves over to disentangle it — not an easy process. "This is actually my first time untangling a bat," Ralston admits. "He keeps getting his arms stuck though." She calls Bennett over to assist and the more experienced biologist frees the little bat from the net, being very careful to avoid tearing the wings or breaking its toothpick-thin bones.

"This must feel like some kind of alien experience to them. You know how people describe their alien experiences as these bright lights and then all these invasive body examinations happening? And of course that's exactly what we're doing." - Alyssa Bennett, Fish and Wildlife researcher

Bennett, a small wiry woman in jeans and a checked flannel shirt, runs her hand underneath her baseball cap to remove an attacking mosquito. While everyone else on the team is slapping their arms and coming up in giant welts, Bennett seems immune to the insects. Or, at the very least, immune to the annoyance they cause.

But she's spent a lot of time thinking about how her actions must feel to the bats she studies. "This must feel like some kind of alien experience to them," she muses. "You know how people describe their alien experiences as these bright lights and then all these invasive body examinations happening? And of course that's exactly what we're doing. We shine bright lights in their eyes. They were just out foraging for the night and then this very strange bizarre scary thing happens. And then we take all these measurements on them. And then we let them go! And they must say to their friends, 'This crazy thing happened. I was just flying around and then this crazy thing happened.' And their friends are like, 'Right.'"

The captured bats are gently lowered into a small cloth bag that is carefully tied up so the Houdini-like bats can't squirm out. The team tries to work quickly and to handle the bats as little as possible. As alien an experience as it is, Bennett wants to keep their stress levels down. But she acknowledges that the discomfort for the bats is worth it: This research is critical to finding a cure for White Nose Syndrome.

Since the disease was found in New York caves in 2006, it has killed more than five million bats and has spread to most of the states and Canadian provinces in the eastern side of the continent. Eleven different hibernating species are affected by the fungus that causes the syndrome. The fungus can cause damage to the skin and wing tissue. And infected bats often wake during winter hibernation and fly out of the caves, where they die of starvation and cold. Mortality rates hover around 90 percent.

Alyssa Bennett and Kerry Monahan administer water to a bat that has been trapped for research. Since WNS was found in New York caves in 2006, it has killed more than five million bats and has spread to most of the states and Canadian provinces in the eastern side of the continent.
Credit Jane Lindholm / VPR

With 13 bats trapped and bagged, the team gets to work collecting vital statistics and samples. With headlamps illuminating their work, they spread test tubes, rubber gloves, swabs and a weighing scale on the bed of Bennett's truck. They're collecting data for a couple different research projects that scientists have asked them for help with, and each has a different protocol with very specific — and sometimes confusing — instructions.

Bennett gently picks up a bag, and with a gloved hand she removes a small bat. It weighs little more than a nickel. Holding it up to the light, Bennett speaks to the bat in a soft voice. "You're very light-colored. You look like a young bat. I'm going to bet that this is a young of the year." Little brown bats have a range of coloring, all in the brown scale, but the young often have a lighter color than the adults. This one is feisty, squirming and chirping and trying to bite the purple glove that's holding it.

The team checks its vital statistics: species, gender, weight, height, etc. Part of the research they're doing involves taking wing biopsies, but the professor in New York has specified only adult bats for the wing sampling, so they run a few other tests and release her into the night.

The adult bat research is geared towards figuring out why these bats have survived White Nose Syndrome. So they're sampling tissue, taking swabs of the bacteria on the wings, and using other research to see what makes the survivors different. Could it be their location? Something in their underlying genetics? Or maybe something unique about the microbiome on the survivors' wings.

"And, in that last scenario, the bacteria that's on their wings," Bennett explains, "people are actually looking into possible treatments for White Nose Syndrome where you might actually take something that already lives in the environment of the bat, in the cave or mine, or is on their own body. And if you were to in some way just add more, for example, of that beneficial bacteria, could you in fact crowd out the fungus or protect the bat more? Could you protect bats that are more highly affected? So they're actually taking this information about the survivors and they're trying to find out if that's something they can apply to any treatment options."

Vermont Fish and Wildlife technician Kerry Monahan examines a bat's wings for signs of White Nose Syndrome. Little brown bats can live 20 or even 30 years, so with any luck, not only will this tiny bat continue to thrive, she might help ensure the survival of her entire species.
Credit Jane Lindholm / VPR

As the team goes through the bats they've collected, sampling wing tissue, swabbing for bacteria and even sometimes offering water to the bats through a tiny straw if they look dehydrated, they find one that's already been banded. They can't tell when the bat was banded just by looking at it, but when Bennett gets back to the office after a night in the field, she makes a remarkable discovery. This was one of the very individuals that the department banded back in 2006.

Bennett says it's very exciting to find this bat, but just because she and a few of her colony-mates have survived, doesn't mean little brown bats are in the clear. "Because the truth is, we're still seeing this species and the northern long-eared bat appear dead and dying outside of our largest hibernacula that we monitor in the winter. So knowing that and knowing there are concerns that we're seeing a lower reproductive rate than we maybe did before White Nose Syndrome, those things do have us concerned still that this bat will hang on, even though their numbers seem to be stabilizing at this 10 percent level."

At the best of times, little brown bats only have one pup a year, so recovery will be slow and no one alive today will be around to see numbers like we had before White Nose Syndrome. Nonetheless, Bennett says it is a hopeful sign for the longevity of the species to encounter a bat that was banded back in 2006. It means this bat is at least 10 years old. "And not only that, but she had survived every winter that White Nose Syndrome has been known to be in Vermont. And that, I think, is an amazing feat. And she had some scars to show for it."

Little brown bats can live 20 or even 30 years, so with any luck, not only will this tiny bat continue to thrive, she might help ensure the survival of her entire species.