Minding the Microfauna

As a mammal specialist for the DNR’s Minnesota Biological Survey, Melissa Boman keeps tabs on small, unsung creatures that don’t often win popularity contests or make it onto wildlife calendars, yet play important roles in ecosystems. She calls them “charismatic microfauna.” Since 2016, Boman has worked with mice, shrews, lemmings, and voles, and has occasionally helped with salamander and turtle counts. However, a good chunk of her efforts go toward Minnesota’s bats, which are facing a worse prospect than simply being misunderstood: white-nose syndrome, a deadly fungal disease that since 2006 has marched across North America and since 2015–16 has wiped out huge numbers of Minnesota’s cave-hibernating bats. When she’s not checking bat boxes, crawling into caves, or wading through bogs in search of little wriggling creatures, Boman also fly-fishes, paints outdoor scenes, and is finishing a master’s degree in natural resources and environmental sciences at the University of Illinois Urbana-Champaign. We caught up with her in the winter as she was looking ahead to surveying caves for bats at locations including Soudan Underground Mine at Lake Vermilion–Soudan Underground Mine State Park and Mystery Cave at Forestville–Mystery Cave State Park.

Q | You do winter bat survey work in caves where bats hibernate. Where, when, and how do you do these surveys? We monitor a subset of caves annually on a rotating basis. Some of them, like Soudan Mine and Mystery Cave, have been monitored every year for many years. Soudan Mine’s been monitored since the late ’80s. Typically we go in about February to do a bat count in their hibernacula, the places where they hibernate. We document what species are there, where they are roosting, evidence of white-nose syndrome, if we’re seeing any bats that have died—just monitoring these hibernacula to see how things are changing with white-nose syndrome.

Q | The disease has been pretty bad for Minnesota’s bats, hasn’t it? Yeah. In Minnesota, we’ve already seen our big declines. The bat population in Soudan Mine has declined by over 97 percent since the disease arrived in Minnesota in 2015-16. And it’s a similar story for Mystery Cave, where our last count documented a 94 percent decline. Those figures pretty much refer to little brown bats, our most abundant species in the hibernacula that we have. We definitely have declines for tricolored bats and northern long-eared bats, our other two cave hibernators. But the little browns are really the drivers of those declines. The tricolored and the northern have both recently been federally listed as endangered, and the little brown bat is under review. 

Q | What are the prospects for these populations that have been so decimated? Is it possible for them to come back after the disease has worked its way through? We won’t see that in our lifetime, unfortunately. A lot of people think that bats are like mice where they’re having a lot of babies at a time. But actually, the little brown bat has only one pup a year. That’s a pretty low reproduction rate for the amount of decline we’ve seen across their populations. So in our lifetime, we probably won’t see bats return to the levels they were pre-white-nose syndrome. In Europe, they’ve always had lower numbers of bats than in North America. And it wasn’t ever really known why until white-nose syndrome came about. It seems like Europe also went through this extreme bottleneck when a lot of bats died off due to white-nose syndrome, but now they are capable of roosting in caves with the fungus, though their populations are much lower than ours. So the thought of where we’re going is that we’re going to have bats that tolerate white-nose syndrome and cohabitate with it, but we won’t see the numbers of bats we saw before.

Q | You seem to have an affinity for bats, like they’re more than just a species you study at work. Yeah. They’re just super incredible animals. I was always interested in kind of the underdogs or the charismatic microfauna, I like to call them, because they don’t get any attention. And so when I started learning about bats, I was just completely blown away. They’re such an incredible animal. And as I’ve learned more I’ve come to put them in a category along with primates, gorillas, and cetaceans in that they’re incredibly intelligent and they’re incredibly social.

Q | What benefits do bats bring, and what do we lose when we lose these big bat populations? Just on the landscape itself, they’re so important for insect control. For example, in forests they eat a lot of beetles and moths that may impact forest health, or that may decimate certain tree species. They also eat a lot of agricultural pests that could help us reduce the amount of pesticides we use. But then there are a lot of things that we’re learning about bats that can contribute to our own knowledge about aging, for example. Since bats are so long lived, they’re a really interesting species to study for the aging process. And they have an extreme spatial memory. Because their winter habitat is so limited, they have to know where multiple locations are for cave systems. In the summertime, they have to know where roost trees are, or their building roosts. So studying their brain and understanding that spatial memory can also help us understand how diseases like Alzheimer’s work in our own brain. And so that’s just one part of research that a lot of folks don’t think about with bats. There’s a lot that we can learn from them aside from the benefits that they provide ecologically to us.

Q | You’re working on a project involving bat boxes in state parks. Can you tell us a bit about that? That’s a big project we at MBS are working on in partnership with DNR Parks and Trails. We’re doing essentially an inventory of all the bat boxes that have been installed on any state park lands or recreation areas. We’re investigating the boxes to see what has been successful and what hasn’t been as far as bat occupancy and the numbers of bats in those boxes. I’m interested in improving guidelines for bat boxes, because guidelines so far have been super broad across North America, and there’s actually not much known about preference by bats. The thought has often been that if you put up a single bat box, you’ve got a colony in there and they’re in there all summer, but I think there’s actually a lot of roost switching going on, where bats are coming and going from the boxes depending on what those temperature needs are.

Q | Can bat boxes help with white-nose syndrome by providing an alternative place to roost away from infected colonies? The boxes won’t be used in the winter by bats; they’re just too cold. Most of these bats will still go hibernate, and so far, the emphasis for conservation regarding white-nose syndrome has definitely been focused on caves and winter work. My focus is really on those summer colonies that are the remaining survivors. Research has shown that surviving bats may carry genes that allowed them to store more fat, potentially helping them survive the disease since bats perish when they starve to death. White-nose causes them to be active too much, and when they become active, because their bodies are so little, it depletes their fat reserves and they end up dying. So I want to focus on summer colonies and those females that have survived white-nose syndrome and ensuring that they have appropriate habitat for reproduction. I want to emphasize the importance of having a safe site. We hope that bat boxes provide that, but there just hasn’t been the research to actually see.

Q | Outside of work you’re a fly angler, aren’t you? Yep. I absolutely love it. That’s something I’ve just totally dived into and have had a blast doing. I really enjoy fishing for everything from carp to quillback to pike and bass, even the micro species. It changes depending on the season and what’s going on. Carp isn’t maybe the first species that comes to mind when people think of fly-fishing. They think of pristine trout. But carp are really fun. They’re very difficult. They can see super well; if you spook them, you’re done. Also, you can get really creative with the flies. You tie something that grabs their attention, what I think of as like carp candy, where they are like, “Ooh, what’s that?” And you can sight fish them, which is super fun. It’s amazing the diversity of fish we have in Minnesota that you can actually catch on the fly. Pretty cool.