The Sounds of Sunset: Surveying Bats in Hillsborough County Nature Preserves

     

Bats flying into the sunset (Anne Froschauer, CC BY 2.0)

 Most of us don’t get the opportunity to spend much time around bats, but these flying mammals are a common and crucial part of Hillsborough County’s nocturnal scene. They do us a huge service by eating thousands of insects every night, including mosquitoes and other pest insects.  Their appetite for bugs makes our outdoor recreation much more enjoyable, reduces the number of mosquitoes present to spread disease, and even helps to protect crops from insects that may damage them. Bats are a vital part of Florida’s ecosystems, and assessing the diversity of bat species can give us a great idea of an area’s overall biodiversity.

Eastern red bat with three babies (Josh Henderson, CC BY-SA 2.0)

Tricolored bat (Pete Pattavina, public domain)

In last month’s newsletter we introduced you to the Environmental Lands Research Analysts Team (EL-RAT), Bernie Kaiser and Gillian Seymour. EL-RAT has been working on a series of plant and animal monitoring surveys to collect data that will help the county shape and improve our land management practices, including a series of bat surveys that will give us a better idea of the bat species diversity in Hillsborough County.

You may be wondering how EL-RAT is accurately surveying bats at night- after all, they move quickly and can be fairly difficult to spot in the dark. The team has installed bat meters on several nature preserves which records sound in the ultrasonic range, too high for humans to hear. These meters record for ten-day stretches and are triggered by ultrasonic pulses of a certain duration and frequency. Bats use these ultrasonic pulses in a process called echolocation, in which they send out pulses of sound and listen as they bounce back. The sounds that return to the bats’ ears give them information about the surrounding world and allow them to navigate in total darkness.

Bat meter set up on a nature preserve

It would be difficult to listen to this jumble of ultrasonic noise and pick out bat individuals and species. Luckily, EL-RAT doesn’t have to. The team uses a software called Kaleidoscope, which analyzes the sounds recorded by the bat meter. Kaleidoscope includes auto-ID bat classifiers that suggest the most likely species of bat found in the recordings. Once the sounds are organized by species, EL-RAT can manually vet the results to ensure there are no misidentifications.  These data inform us about bat diversity and distribution across the Hillsborough County ELAPP nature preserves. 

Real-time bat call spectrograph

Compressed bat call spectrograph

The data collected from these bat surveys won’t only be used by Hillsborough County. EL-RAT will be working with the Florida Fish & Wildlife Conservation Commission (FWC), helping to develop better range maps for the southeastern myotis bat. In addition, EL-RAT will be working with FWC to participate in the North American Bat Monitoring Program, an interagency program which tracks bat populations all over the country. This information will be collected and then made available to other agencies and organizations, helping different groups work together to manage public and private land in the most effective way. 

At the present, there isn’t much information available about how different land management practices like prescribed fire, vegetative and hydrological restoration, and hardwood reduction affect bats. The survey data collected by EL-RAT will help us and other agencies understand more about the role that bats play in our preserves, how land management affects them, and how we can better safeguard and maintain our bat populations.