Bat droppings lead to new roof

A bat can consume nearly 3,000 insects in a single night.

That’s good for the environment, said Florida Bat Conservancy Director Cyndi Marks.

But, the result of such feasting will cost Sarasota County more than $600,000 to replace a municipal building roof plagued with bat droppings.

Sarasota County commissioners approved a construction contract with Sutter Roofing Company March 5 to replace the roof of the R.L. Anderson Administration Center.

The contractor has to perform an exclusion — a bat-friendly removal process — on the roof before construction can begin on the building located at 4000 S. Tamiami Trail, in Venice.

The county performed a major extraction in 2010 and erected four bat houses near the property for the relocated mammals; the county estimates to have removed 400 bats at that time.

Each house can hold roughly 100 bats and, they are mounted in pairs on aluminum poles on opposite sides of the building, according to Sarasota County Operations and Maintenance Supervisor Dennis Alexander.

Exclusions involve the placement of screens or curtains placed near a building’s entry points that allow bats to leave the roost, but blocks them from returning.

Alexander said bats were reported in the building even before his decade with the county, with at least one exclusion performed within the last 10 years.

But, before the exclusion, bat droppings had already done enough damage to the water barrier within the roof.

“It’s a touchy subject because people really love bats,” said Sarasota County project manager Kim Humphreys.

Florida bats generally live in dead and mature trees or caves, but development has shrunk the number of viable roosting areas. The use of pesticides on crops and gardens has caused a decline in bats’ main source of food, according to the Florida Fish and Wildlife Conservation Commission’s website.

“Bats are really vulnerable because they only have one baby per year,” Marks said.

She said they look for crevices that are abundant in apartments and condominiums.

“Any exclusion work done without a new more bat-proof-type product will not work because bats have a strong homing instinct and there is a better-than-average chance they would return,” Alexander said. Barrel-tile roofs, like that of the R.L. Anderson Administration Center, are the most difficult type of structure to extract bats from because there can be hundreds nestled under each tile.

“They’re really tiny when they’re folded,” Marks said. “They like to snuggle close together.”

And bats can wriggle into a roof through any opening the size of a human thumb.

The roof work includes application of polyurethane adhesive to fill voids between each Spanish tile on the 108,000 square foot building, according to plans prepared by Hall Architects.

It is illegal to kill or trap bats in Florida, and exclusions must happen outside of rearing season, which runs from April 15 through Aug. 15.