Tracking Connecticut's Endangered Bats
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Little brown bats are very social and live in colonies of around 9,000 individuals.
There are nine species of bat that call Connecticut their home. Of those nine, six are year-round residents, the little brown bat, big brown bat, tri-colored bat, northern long-eared bat, eastern small-footed bat, and Indiana bat. During the winter, they hibernate in caves and other sheltered humid locations, known as hibernacula. The other three species, the eastern red bat, hoary bat, and silver-haired bat, migrate south to warmer climes when the air grows chill.
Bats are often regarded with superstition, some of which is based in the fear surrounding their role in the spread of rabies. Bats should always be handled with caution, but the reality is that even in bats, rabies infections are rare, and the benefits of bats far outweigh the downsides. A single bat can eat more than a thousand insects per hour, and they spend several hours per night hunting. Their prey includes numerous agricultural pests, such as cutworms, corn borer moths, potato beetles, and grasshoppers.
A little brown bat with white nose syndrome
Unfortunately, all is not well in the bat population of Connecticut, and the United States in general. White nose syndrome (WNS) is a fungal disease which first appeared in the United States in 2006 and has killed millions of bats since. It continues to spread across the nation, and is considered a severe threat to numerous bat species.
WNS strikes bats during their long winter hibernations. It spreads primarily through contact with infected bats as they roost together in hibernacula, but bats can also contract it from contaminated surfaces. The fungus coats bat noses and other bare skin with fuzzy white growth, which causes them to wake from hibernation and resume activity. Unable to find adequate food during winter, infected bats usually starve. Very few bats are able to overcome infection, and at sites where outbreaks are present, 90-100% of bats can die in a single winter.
In Connecticut, five out of the six hibernating bat species are now endangered due to the ravages of WNS. In order to monitor the impact of the epidemic of WNS on local bat populations, CT DEEP put together a mobile bat acoustic monitoring program in 2011. I volunteered to collect data as part of this program during the summer of 2022, and am excited to have been a part of such important work.
My car, with microphone magnetically attached.
Twelve 20-mile routes are being monitored for bat activity throughout Connecticut. These routes stretch across unlit backcountry roads, avoiding the artificial lighting that affects bat behavior. I volunteered to help monitor the Greenwich transect, which runs from north Greenwich, through Stamford, and ends in New Canaan.
Data collection drives start an hour after sunset, and only take place in calm weather. Bats navigate using echolocation at frequencies too high for human ears to hear. I mounted a magnetic microphone to the roof of my car, specially attuned to these high frequencies. The microphone was connected via USB to a laptop on the passenger seat of my car, which tracked my location while simultaneously recording the bat calls detected. A special software called SPECT’R III converted the bat vocalizations to visual format, which let me see the calls recorded in real time as I slowly drove through Greenwich’s dark roads.
The bat microphone
As I drove and heard the squeaking bat calls fed through SPECT’R III, it became clear that bats were numerous in northern Greenwich. The visualizations produced by SPECT’R III implied the presence of several bat species, but their identity can only be revealed by CT DEEP scientist analysis.
My volunteer colleagues and I run these bat surveys from July through mid-October, at which point bat activity declines. Data analyzed from the 2019 acoustic surveys shows that Greenwich is home to many bat varieties. The big brown bat is our most common local bat. Though the big brown bat hibernates, it has shown incredible resilience against WNS infection, and has not experienced the precipitous population decline felt by many other local bats. It is the only hibernating Connecticut bat species which is not presently endangered.
The next most populous bat species recorded in Greenwich is the migratory eastern red bat. Small numbers of the migratory hoary bat and silver-haired bat were detected as well. Where Greenwich really stands out is in our number of endangered Myotis genus bats detected. This genus includes the little brown bat, eastern small footed bat, and northern long eared bat. Greenwich had the highest number of Myotis bats among all locations surveyed in 2019.
I look forward to seeing the results of our current year’s bat survey, and am very glad to have been part of it. For more information, visit the CT DEEP page on Bats in Connecticut.
Kate Dzikiewicz, Science Curatorial Associate
