Is the coast clear for tricolored bats?

Tricolored bat with visible symptoms of WNS from Chickamauga and Chattanooga National Military Park, Georgia. Photo credit: National Park Service

This winter two scientists will set out to learn  whether tricolored bats that use winter roosts other than caves and mines are susceptible to a deadly bat disease in the coastal plains and forests of North and South Carolina — two of 38 states in the bats’ range.

In the winter of 2016, Dr. Susan Loeb of the U.S. Forest Service and Clemson University and Assistant Professor David Jachowski of Clemson did a pilot study of tricolored bats roosting under two bridges in the upper coastal plain of South Carolina. They found that some bats left the bridge for several days and returned, suggesting that they were using alternate roosts. However, because the researchers did not track bats to these roosts, where the bats were going was unknown.

Now the researchers are expanding their study to find out what alternative roosting sites tricolored bats use and if the behavior of bats and environmental conditions there can protect them from the disease white-nose syndrome (WNS).

WNS, caused by the fungus, Pseudogymnoascus destructans, or Pd, was discovered in New York State in 2007. Now confirmed in 31 states and 5 Canadian provinces, the disease has wiped out some populations of several hibernating bat species, including tricolored bats. At hibernation sites where white-nose syndrome has affected tricolored bats, average overall declines of these bats have been more than 75 percent. As observed by Loeb, these declines have been even higher at some sites in the south.

In their pilot study, Loeb and Jachowski discovered that what sets coastal plain habitats apart is a striking potential difference in temperature tricolored bats encounter at more exposed and warmer sites than at mine and cave habitats.

Temperature is critical to the spread of the WNS fungus because any body temperatures above 64 degrees Fahrenheit might mean a greater chance for the bat’s immune system to fight the fungus over the winter, Loeb said.

She said, however, that such sites might be a double-edged sword. If body temperature remains high, a bat will be less able to enter an extended state of torpor, a short form of hibernation that can last only for a few days. Possibly because of the warmer climate, the coastal plains populations of tricolored  bats might only hibernate on a daily basis to conserve energy.

If bats are able to escape WNS in these alternative habitats but remain more active due to higher outside temperatures, they must forage to survive. Finding available insects in the winter, even in the Carolinas’ warmer coastal plains, might be challenging for the beleaguered bats.

Now, with  $125,925 funding from an FWS research grant, Loeb and Jachowski plan to expand their search for the bat’s winter habitat under bridges and in trees across the coastal plains of the Carolinas. They will be joining the ranks of other FWS-funded researchers such as Dr. Jeremy White in Nebraska and State Biologist Cory Mosby in Maine who have turned their attention to small bat hibernation habitats other than caves and mines.

“The decline of tricolored bats in the southeast is concerning. When the disease first arrived in the region, researchers expected it to not be as bad because the bats could forage.  In some populations, we are seeing 90% declines.” – Susan Loeb

To measure body temperature and foraging, Loeb and Jachowski’s team will outfit temperature-sensitive radio transmitters on the bats at their winter roosts to document body temperatures and activity levels. They will use the transmitters to track bats to what might be an array of winter roosting types in this area free of caves and mines.

When the researchers capture the bats, they will swab and inspect them for the fungus and record data about the roost, such as tree height and cavity depth that might affect temperature. They will also collect fecal samples at the roost site and from the bats to determine whether the bats forage in winter.

Loeb said the study will contribute to a better understanding of bats’ susceptibility to WNS in the southeastern U.S. When the disease was first documented, researchers had hoped the region would host roosts that would be warmer than the northeastern caves and mines where the disease was first found, suggesting that the fungus would not spread to areas where wintering bats’ body temperatures would be higher than the critical 64-degree Fahrenheit threshold. In years since, however, researchers have found that even caves and mines in the southeast are cold enough to allow Pd to thrive.

“The decline of tricolored bats in the southeast is concerning,” Loeb added. “When the disease first arrived in the region, researchers expected it to not be as bad because the bats could forage.  In some populations, we are seeing 90% declines.”

Now with exploration of alternative roosts in the southeast, scientists hope some tricolored bat populations might survive if they can find warm roosts and insects to eat during lean winter months. And in the race to help bats survive WNS, hope is a good place to start.

Echo-Locate your Favorite Bat Story

It’s #BatWeek and we can’t stop talking about bats! What is more fascinating than the small flying mammals that help farmers manage pesky bugs? Go batty over our stories of the nighttime critters and the work being done to save numerous bat species. From research studies to citizen science, we cover it all in an engaging story map where you can find stories from across the country.

White-nose syndrome, a deadly disease in bats, is spreading rapidly through the United States and Canada.  With many bat species on the decline, biologists race to save species and learn more about preventing the spread.  Many stories on this map share the great work being done to provide new bat habitat for bats and control WNS. Spreading the word and educating about WNS allows us share their crucial role in managing agricultural pests and encourage others to do what they can to protect bats in their area.

Click here to view the interactive bat story map.

 

For more on bats visit BatWeek.org.

 

Bats and farmers: Allies in the fight against agricultural pests

Kate Harms of Rodale Institute with bat boxes. Credit: Kate Harms/Rodale Institute

With millions of insect-eating bats killed by white-nose syndrome (WNS), what is the impact on agriculture? Kate Harms wants to find out. She’s the principal investigator on Rodale Institute’s project on bats as biological controls of insect pests, which uses bat call detectors to identify where bats are active and installs several configurations of bat boxes to measure their use by roosting and breeding bats. Goals of the project at Quiet Creek Farm and North Star Orchard in Pennsylvania are to find ways to attract bats and forge alliances with farmers to make habitat for bats, especially in areas with great losses from WNS. Recently, I spoke with Kate Harms about her research, the decline of birds and bats that eat insects and how to help bat populations rebound.

Gretchen: Maybe you could start with how you started with this research?

Kate: When I finished grad school, it was around the time that WNS was getting active around here in Pennsylvania. I started working with the state game commission doing the Appalachian Bat Count as a citizen scientist and hosting a public event on WNS. When I began working at Rodale, I started talking to them about bats as insect pest management. We are a research institute, and our work focuses on projects that help the organic farming community. I remember when WNS first began to spread, the organic farming community spoke up about the need for cave closures. They knew how important bats are for pest control. When you’re an organic farmer, you need more than one tool to get through the season. Bats are just one of many tools. Some farmers use bird houses, bat houses, and natural insecticides. I received research grants from Northeast Sustainable Agriculture Research and Education, the Ian Somerhalder Foundation and Patagonia.

We’re concentrating the research on the Northeast U.S. I wanted to look at how bats act in an agricultural setting, both organic and conventional, vegetables, orchards and grain crops. We also looked at tree lines and riparian buffers and how bat activity occurred on the natural landscape and whether bat activity increased on organic farms. That first year of research showed that tree lines were very effective in attracting bats, no matter the commodity. Going into the second year, we looked at how bat activity decreases from tree lines by measuring activity at 50 feet away from the tree line and again at 100 feet.

I can also look at what species of bats we have by analyzing their echolocation calls. I don’t see many little brown bats during my monitoring. That is the cold hard truth of it. They are still around, just not in my research areas. We do get some migratory bat species but mostly I see big brown bats, which are fantastic at eating the agricultural pests, and there is research showing insects in their diet are some of the major agricultural pests.

Obviously, it’s tough to tell a farmer what bats can do for them because our populations were hit so hard by WNS. But we still have a viable population of big brown bats, and we should start with that and support the other species the best we can, in hopes of recovery. It’s about making the farmers allies with the bats so that they can work together. Farmers can help by putting up bat boxes for roosts or managing their roosts in barns so that they can reap the rewards of bats.

Gretchen: Does how you build the box attract different bat species?

Kate: Some species prefer to roost in trees, but the boxes we use should attract big brown bats, little brown bats and even Indiana bats. It’s not the style of the box so much as the size. Bats like thermal stability. The bigger, the better, but how big is the question. There can be a huge price difference by size.

Big brown bats in bat box. Credit: Terry Lobdell

Gretchen: Do you have a web site you point people to for building their own boxes?

Kate: Bat Conservation International — I always point people there. They have tips for bats all around the world. But, we have a guy, Terry Lobdell, that makes them himself and created his own manual (see Bat House Plans). He’s from the Erie area in Pennsylvania and has a lot of success with getting bats to use his houses.

Gretchen: One of the things I’m doing is talking to farmers at our farmer’s market in South Dakota to gauge their awareness of the decline of insectivores such as bats because WNS was recently discovered in Nebraska. Now we’re on the leading edge.

Kate: We need to get the information to the farmers.

Gretchen: I count nighthawks around sunset and I see the changeover at sunset when nighthawks are active and eating insects and then, bats emerge over the tree lines. Here in South Dakota, it’s the Great Plains, and there is native forest only around riparian areas. The woodlots were planted as wind breaks after the Dust Bowl. So, I am always curious about the insects there. Your research has far-ranging impacts.

Kate: I think they use the tree lines for travel corridors and safety. Some roost in the trees so they may be sticking closer to roosting areas.

When you’re an organic farmer, you need more than one tool to get through the season. Bats are just one of many tools.

Gretchen: Is there any connection between the assemblage of insects and trees?

Kate: That’s another thing we could look at if they are more active near the tree line because of the additional food source it provides. I did not get into doing diet work in my research. It’s a pretty heavy work, the DNA extraction to identify insect species and analysis was going to be more time consuming than this project allowed.

With anything like that, though, it adds diversity to the research. With crops, there are different life cycles of insects that prey on them because the larval stage of moths will do the most damage, and bats can kill the adult moths. Trees may offer another source of food for bats as the insects fly around the trees and use them as habitat. It’s extra food security for the bats.

Gretchen: The insect question is another beast altogether.

Kate: Some people have done that diet work looking at bat guano and proven that agricultural pests like stink bugs, leaf hoppers, and moths make up the majority of the bats’ diet. It’s very hard to identify insects in guano by microscope but DNA work is helping with that.

Gretchen: Are you looking at the effects of bats on insects around livestock?

Kate: We have not, but I know people have been asking. Certain flies bother their livestock. I guess it depends on how active the flies are at night when bats are active.

Gretchen: It’s a good case for having several kinds of insectivores around during the day and night.

Kate: Absolutely, that’s the neat thing. One farmer said to me: “There’s a night shift. When I go home, the bats take over.” And I love that. The bats are there to take care of the insects for him.

One other thing: We are working with Kutztown University in Pennsylvania. We are looking at guano to see what’s remaining of herbicides and insecticides in their systems and fecal matter. We are looking at numerous pesticides especially neonicotinoid insecticides. If the bats are eating their weight in insects every night, and those insects are exposed to the pesticides, will we find the residuals in the bats guano? They think these new generation of pesticides are targeted just to the crop and are not in the environment as long. And yet, we are finding drift and run-off from spray leaving the target area, exposing our ecosystems outside the agricultural area and our pollinators. I know there is a push for a ban on neonicotinoids, but they haven’t done it yet.

Gretchen: People in South Dakota are looking at neonicotinoids and how they affect the emergence of aquatic insects, fish and amphibians. But they haven’t moved beyond that into other areas of the food web. I’m eager to find out how that affects insectivores like bats, swallows, swifts and nighthawks.

Kate: I think farmers should know that if they are using an insecticide on something that could build a resistance to it in the future and at the same time if they are also harming other beneficial biological controls. That’s not sustainable, and we should have a better way to assess that risk.

Gretchen: So, have the farmers there had a response to the decline in bats? I know in Maine, they have had an emotional response to losing their bats.

Kate: I hear it from the public more often. Not farmers, necessarily. People often say they don’t see the bats in their backyards like they use to. Maybe I’m not hearing it from farmers because they put a whole day of work in the field, and they are not sitting out at night. But I do hear people who used to watch the bats on their porch at night and they notice they don’t see them much anymore. Some people still have bats and they enjoy watching them. Education is important. They don’t want them in their house. But they are receptive to having them around. I think there are ways to get the public involved more. I always joke that they could sit on their porch with a glass of wine and count them as they emerge. Hey, it’s citizen science.

Gretchen: A little backyard bat watch would be great. They do a backyard bird watch.

Kate: Yes, definitely.

Gretchen: Anything we haven’t covered?

Kate: I see how much public information is lacking. People are hungry for information. And if you show farmers how to do it and how effective they are, and if you can get farmers to take time out of their day, they put up bluebird houses and other bird houses. They can do the same things with bats houses. If you can put up bat boxes, more will come.

Gretchen: I like the quote from Field of Dreams: “If you build it, they will come.” The missing piece is how important bats are, and that’s what you’re doing.

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For more information and to find your local contact, visit whitenosesyndrome.org.

This interview has been edited for clarity and length.