The author helps his colleagues install mist nets around a pond.
YELLOWWOOD STATE FOREST, Ind. – An hour before the sun goes down, my colleagues and I arrive at our site: a human-made pond in the middle of the forest. The high-pitched croaking of Cope’s gray treefrogs greets us as we get out of our truck. Surrounded by trees and full of salamanders, these ponds are an essential water resource for our forest-dependent bats. We do a brief survey of the site, then set up our mist nets around the pond’s perimeter. We’re hoping to catch our target species – the Indiana bat, Myotis sodalis.
Once twilight sets in, we open our nets. Every eight minutes, one of us checks the nets to look for captured bats. We set up our workstation, then work quickly to process the bats. We wear coveralls, clean gloves and face masks to prevent the spread of fungal spores or other diseases to these bats. Each bat is measured, weighed and has its wings examined for signs or symptoms of white-nose syndrome, a fungal disease afflicting bats across the Midwest and Eastern U.S. We also assess each bat’s reproductive status and age. This time of year, late May through early June, we mostly catch pregnant females and nonreproductive males.
The team uses mist nets around a pond to capture bats. The bats tend to roost in dead trees and rear their pups in settings like this.
Indiana bats are an endangered species. Both habitat loss and white-nose syndrome have negatively affected their populations. Because these bats depend on ephemeral dead trees as day roosts and sites for rearing their pups during the summer, we work hard to find and identify high-quality roosting habitat on managed forest landscapes. Our data will help land managers make better-informed conservation decisions.
The author gathers data on a big brown bat, Eptesicus fuscus, captured in a mist net.
We capture several Eastern red bats, Lasiurus borealis, and a big brown bat, Eptesicus fuscus, but Indiana bats are more elusive. After several hours of netting, we finally have success. We capture a pregnant female Indiana bat. Now my part begins.
My role at this site is to attach temperature-sensitive radio tags to reproductive female Indiana bats. We’ll use these tags to track the bats to roost trees during the day and to monitor their body temperatures.
For reproductive female bats, maintaining a high body temperature is important to facilitate the growth of their pup. But if their roost temperatures get too low, the females may go into a state of torpor, actively lowering their body temperature and metabolic rate to save energy when it is too costly to remain warm. While torpor saves energy, it can slow down the growth of the mother’s pup and affect its chances of survival. Therefore, understanding when bats choose to use torpor or maintain a high body temperature and what roosts they select during these time periods is critical to identifying high quality habitat for these bats.
Crawford places a tiny temperature-sensitive radio tag on the bat’s back before releasing it.
I carefully solder the leads of our transmitter to activate the battery. My colleague, Indiana State University graduate student Elizabeth Beilke, verifies that the transmitter is working with the radio receiver, which beeps at steady intervals to indicate that the tag is active. She holds the bat securely while I carefully trim the fur between its shoulder blades so that we can attach our tiny transmitter to its skin with surgical glue. We wait for the tacky glue to dry, and then release the bat. It swoops off my hand and flitters off into the night to continue its pursuit of insects and other arthropods for its midnight snack.
We finish our netting just after midnight, and we are satisfied with our work. Our crew of four – including field technician Jahshua Sanchez and U. of I. undergraduate student Jacob Delgado – works to break down the nets and decontaminate our gear. We head back to our research station for some much-needed sleep. Tomorrow, we’ll start tracking our bat to locate its day roost. Our hope is to better understand this species’ roost preferences and thermoregulatory behaviors.
Editor’s notes:
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