An Unexpected Visitor: Genetics reveal unanticipated roost use by hoary bat

Within the deep, rolling wooded ravines along the Embarras River south of Charleston is a biologically rich area known as Warbler Ridge. This 1,059-acre site contains five areas protected within the Illinois Nature Preserves Commission system: Warbler Woods Nature Preserve, Embarras Ridge Land and Water Reserve, Warbler Woods North Land and Water Reserve, Warbler Bottoms North Land and Water Reserve and Warbler Landing Land and Water Reserve.

Preserved since 2011 by Grand Prairie Friends, showy spring wildflowers, colorful fall foliage and a diverse avian community, especially during spring and fall migrations, attracts visitors. But lately, bats are drawing the attention of volunteers and visitors—and since 2018 attracting a team of Illinois researchers.

Nine of the 13 species of bats in Illinois make their home in Warbler Ridge Conservation Area, including the federally endangered Indiana bat and likely the federally threatened northern long-eared bat. Grand Prairie Friends are working to enhance maternity roost bat habitat at Warbler Ridge. As a long-term strategy, trees have been planted along the Embarras River. Ameren Illinois assisted with installing power poles with artificial roost structures for bats to use until the trees mature and are able to naturally provide roost sites (see Communities Supporting Bat Communities).

Genetic techniques allow us to observe and record information even if we never actually see the animals. Passive sampling like this means biologists can monitor a wider geographic range and collect more data with less work. Before these tools became available, to confirm that a species is using a space both the researcher and the bat had to be present in the same place at the same time. The researcher also has to have a good enough look at a small, quickly moving, flying bat at night to see diagnostic features that are often tiny.

Are Bats Using Artificial Roost Sites?

Bat guano collected from one of the roosts in 2020, was genetically analyzed and identified as that of an Indiana bat (Myotis sodalis). In 2021, a bat carcass collected from the site was also was identified as this federally endangered species.

Genetic tools allow us to monitor the progress and assess efficacy of recovery efforts. It can sometimes feel emotional when you see that conservation really is possible. So much effort and heart went into creating this amazing habitat, and when we confirmed that Indiana bats had not only returned to the area, but had also been reproducing, it renewed our hope that this species can make it in Illinois.

To further understand the use of artificial roosts, on September 19, 2023, members of the Illinois Bat Conservation Program (IBCP)–a team of researchers from University of Illinois’ Prairie Research Institute—visited Warbler Ridge and Warbler Bluff to collect bat guano from underneath artificial bat roosts on the property. Eight vials of guano were collected with sterile forceps from seven roosts at Warbler Bluff and Warbler Ridge Conservation Area, which were divided into a North and South site. The samples were collected from directly underneath each roost and the selection and collection of individual guano pieces was random to avoid sampling bias for larger species. The guano was preserved with silica beads in vials, which prolongs the viability of DNA present without the need of ethanol or refrigeration.

The DNA was extracted from the guano samples and amplified using PCR methods. PRC, or Polymerase Chain Reaction, is a laboratory technique that amplifies DNA sequences to produce millions of copies of a specific DNA segment. Samples were then sent to the Keck Center for Comparative and Functional Genomics to be sequenced, and finally the found sequences were compared to those with known species identifications to determine the species. IBCP has recently added a tool that allows the determination of sex as well as species, which can be useful in the identification of maternity colonies.

Of the eight vials, all but one contained viable bat DNA. DNA can degrade while sitting in the sun and during rainstorms, so it’s not uncommon for some samples to be lost, but in general success rates are high. Three vials contained big brown bat DNA, two contained evening bat DNA and one each documented the presence of a hoary bat and the federally endangered Indiana bat. In addition to bat DNA, these samples are loaded with the DNA of their prey. In this situation we are interested in learning about the bats themselves, but this tool can be used to look at diet as well.

The only unexpected result is the use of an artificial roost by a hoary bat (Lasiurus cinereus), typically a foliage roosting bat, meaning they roost in clumps of leaves on trees and not found in structures.

I am used to processing these samples and seeing familiar species pop up over and over again but when I first saw the hoary I thought I had made a mistake. I went back to the lab and did everything again. I triple checked all my work and it identified a hoary bat. It really goes to show how much there still is to learn about bats, and how important curiosity and exploration is in conservation science.

The collection of guano from underneath artificial roosts does not guarantee this species is using the roost but could have been flying nearby or resting outside the structure. These results warrant additional consideration.

Summary

Many tools exist to explore important questions of bat biology—but bats can still be elusive. At the end of the day, these are small, flying, nocturnal animals and sometimes we need to be creative to peek into their lives. Genomic techniques like this provide researchers unprecedented access to what otherwise remains hidden from us. Analysis of DNA collected under artificial roost sites provides valuable data on the location of bat communities, including species of concern such as the federally endangered Indiana bat, without a researcher needing to be physically present. When the effort has been made to invest in habitat restoration, it’s worth it to see if it has been successful. Tools like this allow us to confirm species presence and reassure land managers that their efforts are effective.

This is a story of how persistence, optimism and creative research can come together to make meaningful impacts on the species we love.

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Jordyn Chace is a PhD student who works with cutting-edge genomic techniques and applies them to conserve local bat species. She started with Illinois Bat Conservation Program in the fall of 2020. In 2018 she graduated from the University of Vermont with a BS in Conservation Biology and a minor in Chemistry. She is passionate about wildlife conservation and believes that in times of pivotal environmental importance we must don our detective caps and fully utilize DNA.

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