I’d like to wish all the bats emerging from hibernation—and blog readers everywhere—a very happy National Bat Appreciation Day! Bat species are unique and diverse, and they are an essential part of our ecosystem. They are also an important indicator of ecosystem health, meaning if bat populations are sustainable and healthy then the rest of the system is probably in pretty good shape. 

My primary role with the U.S. Fish and Wildlife Service (USFWS) is the recovery and conservation of bat species that are listed under the Endangered Species Act as either threatened or endangered. We work with partners on how to conserve the species and their habitat, with the goal of recovery that is sufficiently substantial to remove them from the endangered species list. We were proud to partner with The Conservation Fund and the city of Hannibal, Missouri on a really big and important project that protected the largest hibernating population of endangered Indiana bats ever discovered. 

Indiana bats are quite small, weighing only 0.25 ounces with a wingspan of 9 to 11 inches in flight. Their fur is dark-brown to black. During winter they cluster together and hibernate in caves or, occasionally, in abandoned mines like the one at Sodalis Nature Preserve. During summer they roost under the peeling bark of dead and dying trees. Indiana bats eat a variety of flying insects found along rivers or lakes and in uplands. Photo by USFWS.

Back in 2012, a local caver named Kirsten Alvey-Mudd was assisting with winter bat population monitoring in the area, and decided to go check for bats in an abandoned mine in her hometown of Hannibal. She hiked in and discovered thousands of bats hibernating, and suspected that many of them were Indiana bats. Soon after we were alerted about her discovery in the former Lime Kiln mine, we were able to confirm what she had found. We quickly realized after surveying one small room that we had counted 16,000 Indiana bats, and that was just a tiny fraction of the bats that we could see! The entire population of Indiana bats in Missouri was thought to be 13,000 individuals prior to finding this site, so we had essentially just doubled that estimate within minutes. 

Our first trip to the mine in Hannibal for observation. From left to right: Shauna Marquardt of USFWS, Tony Elliott of Missouri Department of Conservation, and Kirsten Alvey-Mudd of Missouri Bat Census. Photo by Shelly Colatskie: Missouri Department of Conservation.

We realized that we were going to need to return to conduct a proper bat survey at Lime Kiln, and we did so during the winter of 2013. Six teams were assigned to count bats in different sections of the mine for two hours, and each team had four people: a bat counter, a photographer, a data recorder, and a guide. We estimated there were 120,000 Indiana bats, plus a few thousand of five other species of bats, hibernating in the site. When our next study was conducted in 2015, we increased the coverage by enlisting the help of seven teams that worked for three hours each, and that survey counted approximately 168,000 Indiana bats. And then the most recent survey in 2017 got even bigger, with eight teams counting for four hours, and we found approximately 200,000 Indiana bats. 200,000! And that is still just a minimum estimate since we did not access all the bat areas or count every single bat.

Most of the time you’re counting bats in a cluster, not individual bats. Cluster size varies widely—you can have 10 or 1,000 bats in a cluster. The final survey number comes from the combination of manual counts of the small clusters (<20 bats) plus photo counts completed back in the office of larger ones (>20 bats). But accurately counting bats even from a photograph gets tricky—they can roost on top of each other and also pack in really tightly, so it’s hard to distinguish individuals. Photo by USFWS.

The sheer importance of the former Lime Kiln Mine site to the conservation and recovery of Indiana bats—not just in Missouri, but the species as a whole—cannot be overstated. The USFWS made it our highest priority for bat conservation in our region. We worked with The Conservation Fund to use pipeline mitigation funds from Enbridge Inc. to protect the world's largest hibernation site for endangered Indiana bats and create the approximately 185-acre Sodalis Nature Preserve, which was then incorporated into the park system of the city of Hannibal. The city of Hannibal was willing and excited to improve the property and all of the endangered bats that came with it. They were forward thinking and could see opportunities for the community and potentially for ecotourism, as well as the benefits to bat conservation. 

In order to protect the bats and ensure public safety we hired a company to design and build 33 bat-friendly gates of all different types and sizes to secure the entrances. Here Clint Miller (far left), The Conservation Fund’s Midwest Project Director of Conservation Acquisition, leads a group for a hike up to one of the mine entrance gates. Photo by Steve Orr.

This story does seem to have a happy ending. The human residents of Hannibal have a wonderful new park in which to enjoy hiking, biking, and nature, and the bat residents of Sodalis have a safe and protected place to spend the winter months. However, it is difficult to compare the numbers between the biannual bat surveys and conclude that the Indiana bat population is increasing, due to the fact that we increased our level of effort for each subsequent survey. In 2019 we plan to recreate the 2017 survey with eight teams working for 4 hours. That way, we can actually start to compare year to year and look at trends. Right now I’m just happy to say that the population is stable. We haven’t seen a decrease in Indiana bats because of white-nose syndrome, and construction of the 33 iron gates at the mine entrances (to allow bat access but not human) does not seem to have disturbed the bats or caused their use of the site to change. 

I think the Sodalis Nature Preserve is an exemplary example of how the public and endangered species can coexist and interact in a very beneficial way, and how local communities can contribute to endangered species conservation. Every day people visit Sodalis Nature Preserve and walk up to the gates and look in, and the bats are still there roosting where they should be. Sodalis demonstrates that, when set up in an appropriate way, people and bats can share the same space with fun and benefits for all.

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To read more about Sodalis Nature Preserve, check out Clint Miller’s blog post Celebrating National Bat Week With the Dedication of Sodalis Nature Preserve. Helping to create the Sodalis Nature Preserve was one of the most complex yet ultimately rewarding projects he's ever tackled, and resulted in a spectacular haven for bats and humans alike.