May 22, 2012
MADISON - Bats sometimes roost in attics, barns and other warm places to have their young and nurse their babies. People who don't want bats in such places should take steps by June 1 to safely and humanely get them out and seal off their entry points or wait until after Aug. 15 to do so, state bat experts says.
"Baby bats are not able to fly for that first month or two after they're born, and their mothers need to be able to leave to feed and then return to the roost and nurse them, so it's important that exclusions not be done between June 1 and August 15," says Heather Kaarakka, the Department of Natural Resources bat roost coordinator.
"We don't want to leave bat pups and their mothers with no home or separate the mothers from the pups, which would die of starvation," she says. "Excluding bats during that timeframe can also backfire for the property owner - the mother bats will be frantically trying to get back to their pups and will end up finding their way into people's living spaces."
Four of Wisconsin's native bat species are now considered threatened due to a deadly bat disease, white-nose syndrome, that has killed an estimated 6.7 million bats in the eastern U.S. and Canada and is closing in on Wisconsin, raising concerns that these mammals, voracious eaters of crop and forest pests and mosquitoes, might be eliminated. The four species were added to the state's threatened species list in 2011 and it's now illegal to kill these bat species in most cases, and illegal to exclude them from buildings from June 1 through August 15.
There are a few exceptions that may be granted for exclusion during this time, specifically for roosts that are in hospitals, schools, daycare centers and other public buildings in which the bats roosting - and their droppings -- may cause health issues, Kaarakka says.
Wisconsin's four cave bat species emerge in April and May from a winter of hibernating in Wisconsin caves or mines. They move toward summer sites near water to find hatching insects. Females give birth in June and July, with most bats giving birth to one baby a year, called a pup. Bat mothers have their babies, or "pups," in maternity colonies with hundreds of other mothers and pups; male bats are usually solitary roosters.
There are a number of humane ways to exclude bats from an attic or other place where they may not be wanted, says Paul White, a conservation biologist with the DNR's bat program. Excluding bats involves locating and sealing the actual access points to an attic or other part of a structure where bats may try to roost, placing one-way doors at the entrance, and eventually sealing the holes to prevent access.
DNR's Bat Exclusion guide [pdf] provides step-by-step instructions for excluding bats from an attic or other structure.
People who don't want to take the exclusion steps themselves can contact professional bat exclusion experts, White says. Bat Conservation International has a list of bat exclusion professionals who have agreed to carry out this task in a humane way. That list and more information and videos on how to get bats out, can be found on their Bats in Buildings website (exit DNR).
People who don't want bats inside but don't mind having them on their property also can build a bat house as an alternative roosting location; follow instructions in Build a Bat House [pdf] and be patient; the bats may not take to the new digs in the first or even second year, he says.
People with bats in their attic or barn or other structure can help Wisconsin bats out by volunteering to observe and record the bats' nightly excursions or allowing volunteers to track the creatures on their property.
"Monitoring a bat roost is simple and fun, and I've had quite a few school groups, in addition to citizens, get involved," says Kaarakka, who also coordinates this project. "The data we collect from the monitoring effort gets used to estimate summer population levels of little brown bats and big brown bats as well as the distribution of those species in the state.
"We can also use information collected on each roost site to help determine what types of roosts and microclimate those species prefer and share that knowledge with other bat biologists."
People who monitor bat roost sites position themselves so they can see the bats exit against a night sky as they fly out of the roost. Bats begin exiting about half an hour after sunset and will continue to fly out for about 30 minutes.
While away from the roost, the bats feed on insects. A bat can catch an insect every 10 seconds and a nursing female can consume her weight every night in mosquitoes and/or other insects, White says. A recent study estimated the value of bats' consumption of agricultural insect pests at between $658 million and $1.5 billion annually.
People interested in getting involved in roost monitoring, or want more information about the project they should contact Heather Kaarakka at Heather.Kaarakka@Wisconsin.gov or 608-266-2576.
DNR's bat feature page in a Web series "Celebrating 40 years of protecting Wisconsin's natural heritage" contains more information on monitoring bat roots and other ways for citizens to get involved in helping protect bats.
FOR MORE INFORMATION CONTACT: Heather Kaarakka- (608-266-2576; Paul White - 608-267-0813 or Bob Manwell, DNR Office of Communications - 608-264-9248