Bat monitoring shows declines in population


By Mandy Martin

Darke County Parks

Since 2006, White-Nose Syndrome (WNS) has killed millions of bats in North America. White-Nose syndrome is caused by a cold loving fungus, Pseudogymnoascus destructans. The fungus is native to Europe and was first detected in New York State back in 2006. It’s believed to have been spread by humans visiting caves and carrying the spores on their belongings.

The fungus attacks the exposed skin on a bat’s wings and leads to a white, fuzzy fungus that coats their nose as well. The fungus causes the bats to wake frequently during hibernation, weakens the skin, and depletes their energy which leads to death. WNS was discovered in 2011 in a winter hibernacula in southern Ohio. With that discovery, the Ohio Division of Wildlife began 30-mile acoustic route surveys of summer bat populations. There are 11 bat species in Ohio including the endangered Indiana bat. All species of bats in Ohio are insectivores. Bats save billions of dollars each year for the agriculture industry. One little brown bat can consume 1,000 mosquito sized insects per night! Most states have had a 30-90 percent decline in their winter bat populations and Ohio is no different. We have seen declines of 91-99 percent in two of the largest hibernacula (winter hibernation caves) in the state.

Bats are critical to the agriculture industry and are effective insect predators in towns as well. Darke County Parks’ naturalists began participating in the acoustic surveys in 2017. A 30 mile route I designed encompassed Wayne Lakes, portions of the city of Greenville and many rural roads edged with cropland. The equipment used is provided by the Ohio Division of Wildlife and includes an Anabat detector, GPS monitor, microphone and data card. The microphone is mounted to the top of the car and the bat detector records the echolocations of nearby bats. Naturalists drive the route 15 mph in order to pick-up as many echolocations as possible. Bats emit ultrasonic calls through their mouth or nostrils. The sound waves bounce off objects, including insects. Once an insect is detected by the flying mammal, the bat flies towards its meal. The Anabat is able to record each echolocation and scientists can then identify the species based on the frequency. Park staff and volunteers perform two surveys within seven days. The entire process takes about two hours and starts 30 minutes after sunset. After each route is completed, the equipment is returned to Xenia to be processed. Once all of the data is compiled by the Division of Wildlife, the park district receives the report of the local survey. The data shows a steep decline in bat populations overall since 2011. In 2021, the mobile acoustic survey program was redesigned to follow the standards of the North American Bat Monitoring Network (NAbat) protocol. NAbat is a continent-wide effort that is seeking to standardize several types of bat surveys so that data can be shared and aggregated at regional levels. Though the route and other factors have been changed, the equipment remains the same. Darke County Parks will continue to take part in the survey each summer to further monitor our local bat populations. I also hope to participate in bat roost monitoring with the University of Cincinnati this summer. If you have a barn or outbuilding with a large colony of bats, please let me know!

How can you help bats? There are many ways that you can help bat populations as well. For example, feed bats by minimizing or eliminating use of pesticides in your yard. Turn off unnecessary lights as light pollution can deter bats. Promote natural habitat around your home. Leave dead or dying trees in locations that are not hazardous-they could be roosting sites. You can even check out Bat Conservation International’s website for a thorough Guide to Gardening for Bats. In the meantime, scientists are working hard to integrate several methods to treat infected bats and manipulate their winter hibernacula sites to inhibit fungus growth.

For more information, feel free to contact me at mmartin@darkecountyparks or call the park office at 937-548-0165.

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