Posted by Mom on March 15, 2017
In the summer we share our country home with bats. We welcome the work these Big Brown Bats (Eptesicus fuscus) do to control the insect populations. Living across from a large wetland and having a lot of shady gardens, we have an overabundance of mosquitos. During wetter summers they torment us to no end! Given that the bats will eat their own body weight in flying insects during a single night, we gladly welcome these bats.
The mama bats use the barn’s loft as a safe place to raise their young. Typically, such maternity colonies of Big Brown Bats consist of 20 to 300 bats with the majority of the females being related to one another. One evening in May we counted the bats exiting the back of our barn and tallied over 80. Since the females give birth from May through June, all of those bats were mothers. The youngsters still within the barn likely numbered between 80 and 160 (given that the eastern populations of Big Brown Bats tend to have twins, a number closer to 160 young was likely). Our barn could have housed a Big Brown Bat colony of 240 individuals!
We found ourselves in a quandary; we wanted the bats to continue to live alongside us, but did not want them living in our barn and leaving their toxic mess behind. We also know that bats are under attack from a fungus (White Nose Syndrome) that affects their ability to hibernate, leading infected bats to prematurely awaken from hibernation and subsequently die from cold and lack of food. The fungus spreads rapidly throughout the bats as they hibernate together. Being inclined to promoting ecological integrity at our country home, we did not wish to contribute to the demise of the bats by adding habitat destruction to their gauntlet for survival.
A potential problem of removing the colony is that the females will need somewhere to raise their young and if they cannot find an alternative they may leave the area. Their absence will cause a spike in the local insect population for years afterward. To encourage our bats to stay, Dad Harrold built four bat boxes, which female Big Brown Bats can use as maternity colonies. An added attractant to bring the bats to these new boxes is the aroma of the wood… the boxes were built from pine boards recovered from the barn’s loft – complete with bat dropping stains. Hopefully, the returning mama bats will find the smell of these boxes irresistible.
During a mild day in March we hung the new boxes around our property. We had two bat boxes on the south side of our barn which bats already use, so we added another box to the west side of the barn. The other three boxes we hung from large trees where the sun will shine upon them and warm them. Big Brown Bats are traditionally forest dwellers, so we hope they will readily take to the new boxes when they find they cannot enter the barn.
We’re looking forward to spring to learn if our mama bats will move into the boxes. Here’s hoping we still have bats wheeling through the twilight at our country home!
… though I don’t think the Screech Owl roosting on the top of a bat box will be very welcoming.