Bats in our Belfry

Little feets of not-so-big “Big Brown Bats” tucked cozily away in the wall of the Red Barn

Ok, so our Red Barn doesn’t have a belfry, but it does have bats!

How do we know? It began July 23rd, when a large pickup truck with Illinois plates pulled up in front of our Sanctuary office. From the cab emerged researchers from the Department of Natural Resources and Environmental Sciences Human-Wildlife Interactions Lab at the University of Illinois Urbana-Champaign.

Josie Hoppenworth and Hannah Hopper had tracked a tagged bat to the Goat Conspiracy Sanctuary property. Outfitted with a telemetry receiver and directional Yagi antenna, Josie said “we followed the direction of the loudest beep until we locate the bat — which has led us to the Goat Conspiracy.”

She shared that “there’s a lot of wildlife related technology available, but studying bats is uniquely challenging because of their size. For big brown bats, which rarely weigh more than 30g, we glue small (0.41g) VHF radio transmitters between their shoulder blades. The weight and position of the tag is intended to minimize the impact of the tag on the bat’s daily activities (sleeping, nursing pups, flying, catching insects, etc.).”

Meet “Calypso”, who has been named after our own Nigerian Dwarf denizen and ruler of the Red Barn. The shine of her metal identification band was visible on her forearm when they discovered her sleeping comfortably behind a post in the wall of the barn.

Josie told us that the range of a tag is variable and often impacted by the position of the bat in its roost, the presence of buildings and telephone poles, and topography. In one case, they picked up a bat 2.5 miles away, but for Calypso it was only 0.5 miles. The battery life of the tags is 2-4 weeks, but they often fall off or are destroyed before the battery fails.

While we saw a few little feet and bat butts where they were roosting, we were amazed when Josie told us that the first night, they counted 81 bats exiting the barn!

Bat “Calypso” and friends

Calypso is skeptical about all this human to-do over some winged mammals taking up residence in her barn.

We were curious about the technology and their research, and thought other Goat Conspirators might be too.

GC: How many bats did you capture the night you tagged Calypso, and how and why do you catch them?

JH: The night we captured Calypso we caught six bats in total — two big brown bats and four eastern red bats. We set mist nets along forest roads or around water sources to capture our bats. We untangle them and collect information on each individual, including its species, age, sex, reproductive condition, weight, etc.. If it’s a species of interest, we band them and apply a transmitter. While the goal for my project is to track big brown bats to better understand their ecology, our lab’s work is part of the 100-year Hardwood Ecosystem Experiment which has broader goals of understanding how bats respond to forest management.

GC: What is your season/time period for doing this tracking research? Is it year round?

JH: My research is conducted during the summer (May-August) as we’re primarily interested in their behavior during the reproductive season. However, there’s definitely a need to study big brown bats year round as there’s a lot we don’t know about them.

GC: How long do bats, like the ones in our barn, stay in one place? And when and why do they decide to move?

JH: It seems to depend on a lot of factors. Other studies of female big brown bats and our observations of Calypso indicate that female bats using human-made structures are extremely loyal to their roosts. While they sometimes move between a series of structures (buildings, bridges, etc.), they often return to one main roost where they may spend all summer and potentially even the winter. In some cases, bats will return to the same roost over multiple years. We’ve found big brown bats captured in Yellowood and Morgan-Monroe State Forests frequently roost in trees as opposed to human structures, which is not widely documented. The females use cavity bearing trees (mainly American beeches) and often switch trees every 1-3 days. Though, we tracked a female for a week who never switched trees. Males are even more variable in their behaviors. All males we’ve tracked (7 total) roosted in trees with about half switching trees every 1-3 days and the others not moving at all. They don’t seem to be picky and will roost anywhere and everywhere as long as their body fits. It’s difficult to deduce why they switch (or don’t switch) roosts, but I’ll note that bats are logical creatures that are constantly learning. They select roosts that meet their needs which may be minimizing their energy expenditure and exposure to predators or disease. If they move roosts, it’s likely because they think their needs can be better met elsewhere.

GC: When the head out for the night, do they stay out all night?

JH: How long bats forage at night varies based on the time of year and the individual. We’ve found that Calypso leaves the barn at dusk and forages in the state forest for about an hour and a half before returning home. She then seems to make another trip to the forest around 3am. She can make it from the Goat Conspiracy to Yellowwood Forest in about 15 minutes. All of our big brown bats have periodically returned to their roosts throughout the night or made pit-stops to rest and digest their food.

GC: What do big brown bats eat, and how many (for instance) mosquitos will they eat in a night?

JH: Big brown bats eat flying insects like moths, beetles, and mosquitoes. Larger bugs (relative to a 30g bat) provide a greater amount of energy, so we expect them to be consumed more often than smaller insects. Big brown bats can consume up to their body weight in insects per night which would equal… a lot of mosquitoes!

GC: HOW did you count 81 bats? I'm guessing they don't always leave their roosts one at a time for your convenience…

JH: The rate at which big brown bats exit their roost changes throughout the emergence. In total, it took 15 minutes for all of the bats to leave the barn. It started with just one or two individuals leaving shortly after sunset. Then it ramped up to where multiple individuals were flying out at once. Finally, it settled down as the last few stragglers made their appearances. We had people set up on either side of the barn which meant I saw 61 exit on my side while Hannah saw 20 bats.

CG: Why are you studying this particular species?

JH: The big brown bat is considered a common species across most of its range, which encompasses almost all of the U.S., Mexico, and southern Canada. Despite being so common, we know relatively little about how big brown bats use forest dominated landscapes like those present in southern Indiana. This lack of information is what really inspired me to focus on this species for the second chapter of my thesis. Considering that even common species can exhibit sudden and drastic declines (see population trends for northern long-eared bats), it’s important that we understand, protect, and support all bat species regardless of their conservation status.

GC: If you had a chance to give people one message about bats or bat conservation, what would that message be?

JH: Bats provide a number of ecosystem services that directly benefit people. Locally, our bats greatly contribute to pest control and nutrient cycling. Globally, they also disperse seeds and pollinate plants. While our society is reliant on bats, it’s my belief that wildlife also has an intrinsic value which is independent of whether they benefit humans. Bats are amazingly complex and interesting creatures that unfortunately receive a lot of negative attention from the public and media. I encourage anyone with negative perceptions of bats to look into the ecology of the native bat species in their area. The more we understand the wildlife around us, the more we can learn to appreciate them.

We are so appreciative of the efforts of Josie and Hannah, as well as Zeke Herrera-Bevan, Alyse Erenberger, and Tony Cisneros, and grateful to the bats for choosing to stay with us. This has certainly been a welcome adventure. And special thanks to Calypso the goat, for sharing her name and her opinions.

Hannah, Josie, and Calypso, the OG G.O.A.T.