The second largest park in Hannibal encloses 200 acres of nature and history around an old limestone mine. At least 200,000 Indiana bats spend the winter months hibernating inside the mine.
The Conservation Fund, a non-profit group that protects wildlife properties, estimates that about one-third of the Indiana bat population — on both the state and federal endangered lists — live at the Sodalis Nature Preserve.
The Missouri Department of Conservation and the U.S. Fish & Wildlife Service help monitor and maintain the local bat population.
The species was added to endangered lists in the late 1960s because they are vulnerable to disturbances in the very few caves they hibernate in large groups.
The park shares its name with the winged residents. The scientific name for Indiana bats, myotis sodalis, means mouse-eared companion. The name alludes to their appearance and naturally social demeanor.
While there are fences and gates around the area keeping bats and humans safely separated, at dusk thousands of bats can be seen flying in and out of their caves.
According to the Conservation Fund, the mine's microclimate creates ideal conditions for the bats to settle. Factors such as temperature, moisture, humidity and air flow influence where the bats will hibernate.
Mid-April is typically when bats are spotted emerging from hibernation. They are most active during the summer, so June through August are ideal times to spot the creatures.
Rising interest in bat conservation has led Hannibal Parks and Recreation to offer free night hikes at the preserve with local nature educators and volunteers.
Bats of various species are not the only wildlife attractions at Sodalis. "(T)he woodlands of the park contain animals and plants typical of the Mississippi River bluffs including neotropical migratory birds, hawks and owls," said Clint Miller, Midwest project director with the Conservation Fund.
A 2-mile paved trail beginning at the park's entrance takes a loop around the park. Another unpaved trail, the Pirate Ridge Trail, takes hikers on a 1½-mile trek around the park's outer edge.
There is an "extensive off-road trail system ... that connects to other parks and downtown," Miller said.
Sodalis is a destination featured in the Hannibal Parks and Recreation Scavenger Hunt, a free activity that encourages visits to local parks. Motorized vehicles are prohibited on trails, but cyclists are welcome.
Mary Lynne Richards, Hannibal Parks and Recreation's marketing director and recreation supervisor, said the park is a great asset to the town.a
"Hannibal has many parks but few pedestrian trails, so this was a much-needed addition," Richards said. "The fact that it is mere blocks from the downtown, riverfront and Mark Twain’s Home makes it accessible for residents and tourists."