Who is rambling around in my attic, I questioned, as I was trying to sleep. Definitely too big for a mouse. After a few days I decided to call a wildlife inspector. He showed up and popped his head in the attic and told me that I have bats in my attic. I was perplexed. Bats hibernate – that means they basically sleep all winter long. So who was creating the ruckus? The inspector replied that bats cuddle and flop around during the winter. Cuddling sounds adorable but not an overly noisy behavior. “Flopping around” doesn’t sound like ruckus level noise either. When a bat hibernates their heart rate drops from 200-300 beats per minute to just 10 beats per minute, and their body temperature can drop to near freezing. But even in this state of torpor, bats will experience brief periods of awakening, when their body temperatures return to normal for a few hours – their normal temp being 104 degrees F.

The inspector added that because the bats were right near the hatch he couldn’t inspect further to see if there was anyone else up there. It is illegal to disturb hibernating bats. Well, whoever else is up there, I hope that because they found their way into the attic, they can find their way out. And I sure hope the “ruckuser” won’t eat the bats.

The inspector told me that I have Big Brown Bats hibernating in my attic, and that they would be my housemates until spring or summer. There is a short window when you can evict bats before they mate and the females become pregnant. It is illegal to evict nursing moms. If you miss the brief window of time in May, you have to wait until the pups have fledged in summer. That’s right, no evicting small children either. I don’t mean to anthropomorphize, but I just find it curious and wonderful that bats have certain rights to protection and housing that I wish we humans would also do for one another.

I told the inspector I would wait until after the pups fledged. August 1 to October 15, before the frost, is a safe time to send bats flying for a new winter roost. Honestly, I wish I could let them stay but only if they would litter train themselves so that they wouldn’t make a poopy mess on the floor. A representative from the MA Division of Fisheries & Wildlife Natural Heritage & Endangered Species Program informed me, “Guano does not pose any more of a threat than bird or cat droppings would, and it is not toxic or harmful to humans, dogs, cats, or other animals. You can spray a mist of water onto the guano to help keep the dust down, and thus the spores. Also, be sure to wear adequate respiratory protection, such as a N95 mask.” What can pose as the threat are the spores of a fungus, growing in bat and bird droppings, which cause a respiratory illness. So don’t sweep dry – wipe moist.  

The rep also stated, “bat-proof your entire house by blocking all possible entrances that are ½ inch or larger using a good sealing material, leaving the one primary entrance open with a one-way door.”

This spring I will be setting up a few bat houses for the bats to move in to. Bats need at least two dwellings because although everyone hangs out together for most of the year, when the moms are nursing, they kick the males out so the males need a bachelor pad. Go to www.mass.gov/guides/bat-houses for instructions on bat house building and siting needs. Female Big Brown Bats also exhibit a behavior called philopatry, which means a love of place – which I can totally relate to because I love where I live too. “Around 10-30% of female offspring usually return to their natal roost the following year and up to 72% of adult females use the same roost in subsequent years.” (Fun fact found on Animalia) This means I may have my work cut out for me in trying to rehouse these bats but my hope is that their love of place extends through my yard and not just my attic.

There are 9 bat species indigenous to the Commonwealth. All of them are insectivores. These neighbors are worth more than their weight in gold for all the mosquito-eating they do.

4 are considered common: Big Brown Bat Eptesicus fuscus, Eastern Red Bat Lasiurus borealis, Hoary Bat Lasiurus cinereus, and Silver-haired Bat Lasionycteris noctivagans. The remaining 5 are listed as endangered in MA: Eastern Small-footed Bat Myotis leibii, Indiana Bat Myotis sodalist, Little Brown Bat Myotis lucifugus, Northern Long-eared Bat Myotis septentrionalis, and the Tricolored Bat Perimyotis subflavus (formerly called the Eastern Pipistrelle). Of these 5, both the Indiana Bat and the Northern Long-eared Bat are also on the Federal Endangered Species List and there hasn’t been a sighting of Indiana Bat in over 80 years.

The bats hibernating in my attic are Big Brown Bats but how would I know that? First, of all the bats, Big Browns tend to prefer to winter over in buildings and they hibernate together in small colonies whereas Little Browns hibernate more in caves in larger colonies. Visually Little Browns and Big Browns are somewhat hard to tell apart unless you see them together. They both have short brown fur with darker brown wings. Big Brown’s wingspan is 11-13” with a 4-5” body length, whereas Little Browns have a 8.5-11” wingspan and are 2.5-4” long nose to tail. Big Browns’ noses are also broader than Little Browns. Little Brown’s guano is about the size and shape of uncooked rice, whereas Big Brown’s guano is a bit larger, think long grain wild rice, only chunkier. Both species weigh less than half an ounce.

I have other critters who also became housemates this winter, but I am very less enthused about co-habituating with them: House Mice, Western Conifer Seed Bugs, Asiatic Ladybugs, Houseflies, and of all the annoyances, Mosquitoes (I don’t know which specie). Why are Mosquitoes flying around in my house during the winter? I have no idea. I haven’t been able to locate a patch of standing water – must be in the walls. I need to wake up one of those bats in the attic and invite them to dinner.

Resources
Bats of MA at Mass.gov
MassWildilfe Bat House Building Guide
Setting Up Bat Houses in the Backyard

Arianna Alexsandra Collins, naturalist, poet, writer, wild edible enthusiast, and Wiccan High Priestess.

An edited version of this article appeared in the March 2024 edition of The Ashfield News.

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