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.
For more information and to find your local contact, visit whitenosesyndrome.org.
This interview has been edited for clarity and length.