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Surveyors count more than 180,000 Indiana bats at Sodalis Nature Preserve

Indiana bats cluster on the ceiling of a former mine at Sodalis Nature Preserve. Photo by Andrew King/USFWS.

Indiana bats cluster on the ceiling of a former mine at Sodalis Nature Preserve. Photo by Andrew King/USFWS.

By Georgia Parham
Regional Office – External Affairs

Within walking distance of downtown Hannibal, Missouri, sits Sodalis Nature Preserve, a hilly, 185-acre park managed by the city of Hannibal. Among other amenities, Sodalis offers pleasant, leafy trails for hiking and birding. Visitors walking some of the paths will pass by gated openings into the hillside, once used as entrances to the former Lime Kiln Mine. The mine is now empty of miners, but it’s full of endangered Indiana bats. The latest count at Sodalis, conducted in February 2019, confirms its place as the country’s most important hibernation spot for this species, with an estimated 180,801 Indiana bats!

Every two years, biologists and volunteers conduct a count of Indiana bats in hibernacula – or hibernation sites - across the species’ 22-state range. For the 2019 count at Sodalis, more than 45 surveyors gathered in Hannibal to receive instructions on the exercise. U.S. Fish and Wildlife Service bat counters came were joined by bat counters from Missouri Department of Conservation, U.S. Forest Service, Illinois Department of Natural Resources, universities, consulting firms and conservation groups. Local, experienced cavers served as guides for the counters.

With near-military precision, the group formed teams and divided up responsibilities - counter, photographer, recorder - and headed into the mine - with each team assigned to a specific area within the maze-like interior. Armed with cameras, headlamps and maps, the teams spread throughout the mapped area of the mine. Overhead, clinging to the ceiling, sometimes within arm’s reach, were the bats. Hundreds, thousands of Indiana bats, along with a few other species. Looking up within the mine, in some places the ceiling appeared to be carpeted in bats.

Within its assigned area, a team photographer snapped photos of larger clusters while counters tallied small groups and the occasional single bat. Recorders made notes of numbers and location and logged photo numbers for future counting. Working as quickly and quietly as possible, the teams moved through the mine and spoke in whispers to lessen disturbance to the bats overhead. Within three hours, the survey was complete. The humans moved out, leaving the bats in silent darkness for another two years.

Back in offices and labs, biologists counted bat noses in photographs and tallied numbers from log sheets. Shauna Marquardt, biologist with the Missouri Ecological Services Field Office, helps coordinate the survey with Missouri Department of Conservation. Marquardt explained that this was the most involved and thorough survey to date at Sodalis.
“We continue to observe the consequences of white-nose syndrome in the hibernating bat populations of Missouri, with dramatic declines of northern long-eared bats, tricolored bats and little brown bats. While we did not observe the same dramatic decline in the Indiana bat population at Sodalis Nature Preserve, the survey this year was the first to indicate a shifting downward trend that can be attributed to white-nose syndrome,” said Marquardt.

The 2017 survey tallied 197,419 Indiana bats at Sodalis. Range-wide population estimates for Indiana bat should be available soon.

Indiana bats are so named because the species was first discovered in Indiana, although they occur in many states in the eastern half of the country. Their scientific name, Myotis sodalis, is also appropriate: Myotis for mouse-eared and sodalis for companion. These tiny mammals gather in tight clusters to hibernate, from just two or three to several hundred individuals. While Indiana bats seem numerous at Sodalis and a few other hibernacula, the species has experienced drastic declines. In 1967, with a population estimate of 880,000, the Indiana bat was among the first species recognized as endangered in the United States. Today’s population is thought to be less than half that size.

Sodalis Nature Preserve was acquired by the city of Hannibal in 2016, the result of work by the U.S. Fish and Wildlife Service, Missouri Department of Conservation, The Conservation Fund and Iowa Natural History Foundation to conserve the abandoned mine for endangered bats. Purchase of the property, and its ongoing management, is provided by the Flanagan South Pipeline Mitigation fund.

A guide leads the Service’s Karen Herrington, Laurel Hill and other team members into Lime Kiln Mine to survey Indiana bats. Photo by Andrew King/USFWS.

A guide leads the Service’s Karen Herrington, Laurel Hill and other team members into Lime Kiln Mine to survey Indiana bats. Photo by Andrew King/USFWS.

 

Last updated: May 6, 2019