What if you don’t follow the guidance on exclusions?

When bats are found in a building, the human residents typically want them out quickly, and pest or wildlife control companies benefit if they can complete a bat exclusion project quickly.  But it is critically important to make sure the bats have sufficient time to leave.  First, FWC rules require that any exclusion device must be left up for a minimum of 4 nights when the overnight temperature is forecast to be at least 50ºF.  Second, bats are capable of reducing their activity, especially in cool weather, and they may stay inside their roost for several days.  If they don’t leave before their exit is sealed, they will die inside the building.  Finally, if bats are trapped in building walls or attic space, they may find ways into the interior of the building where they directly encounter people.  

Can it really be that bad if all the bats don’t get out?

Yes, it can.  To help convey the potential consequences of sealing bats inside a building, here’s a true account of an incident that occurred in north Florida before the exclusion rules were in place.  In this case a modern county courthouse, 3 stories tall, had Brazilian free-tailed bats (Tadarida brasiliensis) in the upper walls. The bats had entered openings where the brick met the roof.  There were hundreds of bats and, as is characteristic with this species, the odor of bats was noticeable inside the building.   Unfortunately, a proper exclusion was not done; in fact, an experienced bat biologist was not even consulted.  Instead, the maintenance staff began sealing off the openings around the roof edge, over several days.  When the workers finished, they assumed that most of the bats had escaped and that those that didn’t would simply perish unnoticed inside the walls of the courthouse. 

They were wrong -- at least about the unnoticed part.  At first, the only complaints were from people with offices on the top floor who said that the bats smelled stronger and were louder than they were, previously.   Soon some of the bats found their way out of the walls, to the interior of the building where they flew among the offices and hallways trying to find an exit.  Of course, bats flying in the courthouse halls didn’t set well with county administrators, and they contacted a local wildlife rehabilitator to capture the bats.  The wildlife rehabilitator caught dozens of bats each day, much to the relief of visitors and office staff.

But flying bats were the least of the problems.  A week or so after the bats’ exits were boarded and the flying bats were mostly removed, the courthouse staff started smelling an overpowering  odor.  Those with offices nearest the roosting bats sprayed deodorizers and even resorted to lighting candles in their offices to mask the stench.  Soon flies appeared and buzzed along the edges of the windows and trim, or anywhere that emitted the odor of dead and rotting bats.   In a few rooms the odor along the window seams was accompanied by fluids seeping down from the rotting carcasses.   That was enough.  The courthouse had to be closed for a week until the walls were cleaned and the odor reduced.

So, yes it is important to do an exclusion right and to give the bats plenty of time to move out.  Closing exclusion exits early or simply sealing bats in a building is not only illegal and inhumane, it can also expose people to sick or weakened bats.  And if that’s not enough of a deterrent, the example of the rotten courthouse should be.  

Can building repairs be done during bat maternity season?

In most cases, yes! If bats are occupying a building, and structural repairs are needed that will not impact the bats ability to enter or exit, the repairs can proceed.  Some common sense precautions to take:

  1. Workers should be made aware of the bats presence to avoid being startled.
  2. Avoid areas with bats, and immediately leave if bats appear to be disturbed (increased chattering or flying).
  3. Use red lights if needed to navigate in attic spaces to limit disturbance to the bats.  White lights in the work area should be okay, if not shining directly on bats. 
  4. Do not handle or pick up any bats. 

There are bats hanging on the exterior of the house or structure during exclusion.  Is this normal?

When bats leave the roost site, they often forage for most of the night, using alternate night roosts and returning to the building or structure just before sunrise. When bats return to a roost with exclusion material in place, they may stay close to the roost – hanging on walls, under eaves or on netting over their entrance – for the first day. Although they may seem exposed, this is normal behavior and not something for concern. The bats will usually leave the next evening after dark and not return. Fidelity of bats to roost sites and their instinct to return there is a key reason why it is so important to bat-proof a building prior to exclusion. If other potential entrances that were never used before by the bats are left unsealed, these become more attractive to bats once the more desirable entrances are blocked.

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