But is it really bats?

October 16, 2024 11:26 AM

My mom lives in New Mexico where her house has a big outdoor covered porch in the backyard that is quite high with wood beams. At certain times of year she started noticing staining and droppings under the porch and a wildlife guy said it was from bats. She has never actually seen the bats and it seems like they are roosting there at night, not during the day.

I guess the bats come at night and roost in the eaves of the porch? She has tried for years to get rid of them because they poop all over the patio. The wildlife guy said to hang up sheets of aluminum foil but that has not helped.

The whole situation feels a little weird to me because I thought bats were active at night, so why would they be roosting only after dark? She has also never actually seen any bats, although she does live near a wooded area where I would absolutely expect them. The poop I've seen looks a lot like mouse poop.

Since the alleged bats are outdoors she has had a hard time finding a solution to try to get rid of them. I have had a really hard time finding any information specific to bats invading the outside parts of a house, like a covered porch. Most advice is about preventing them from getting inside.

I guess I have two questions here:

1. Does this even sound like bat behavior?
2. How do you get rid of bats that are already outdoors?

posted by forkisbetter to Home & Garden (4 answers total)

I have bats that like to roost in a seldom-used & usually furled canvas sun umbrella that stands in the corner of my yard. Their poop looks like mouse poop. If I want to evict them, I wait until evening when they all fly out, and I open the umbrella and clean up the mess and they find somewhere else for a while. I feel bad because bats are awesome members of the neighborhood and they eat mosquitos. When I see them flying out in the evening I say "ah, there go my bats" as if it was all intentional but of course it isn't.

In your case they probably squeeze themselves into the darkest corners during the day and are very hard to see - roosting bats can be surprisingly tiny. I would see if you can gently evict the bats - at night, perhaps, get up on a ladder with a flashlight to inspect every corner - and install some mesh (hardware cloth) on the underside of the eaves in the porch so they can't get up into the dark corners again. If there is a uniformly exposed surface on the underside of the porch roof they probably won't re-roost there because they can't hide.
posted by niicholas at 11:51 AM on October 16 [2 favorites]

Sounds like maybe bats. They are tiny and can hide very well. They also come to rest and digest a little in between doing bat stuff at night. Bats are more active at sunrise and sunset so I'd camp out and watch the porch at those times, see if you see any flying around.

I second hardware cloth over the eaves so they can't get in there (check with a flashlight at sunset/sunrise to make sure you don't wall anyone in) and building a bat box somewhere nearby, to give them a better option. If you can get an ID of the species, you can tailor the bat box to their preference. It seems like something your local extension office or Fish & Game/Wildlife department might know.
posted by blnkfrnk at 1:13 PM on October 16 [4 favorites]

My understanding is that many bats evacuate right on their way out of their roost -- for instance I had an accumulation of bat poop on my roof right outside the hole that they used to exit the attic.

Is it possible that there are nooks, crannies, or adjacent space (e.g. the attic of the house that the porch is attached to) where the bats are living, and you're seeing evidence of their departure route rather than their roosting spot?
posted by eraserbones at 5:09 PM on October 16

Bats do sometimes roost during the night in places that are different from their day roosts. So they could be using the porch just at night. And as pointed out above, they're small and likely to hang out in corners and crevices so they could be there during the day even if your mom has never seen them. Bat droppings look similar to mouse droppings. It certainly seems possible that the droppings are from bats.

If your mom wanted to try some detective work, she could clean up all the droppings or put down an old sheet or a tarp over the area and then check in the morning and at the end of the day for a week or so to see what time of day new droppings are appearing.

She could also try putting down some flour in the area where she finds droppings and then checking it for little footprints, which she would expect to see if mice were the culprits. If new droppings show up with no tracks, that would suggest bats.
posted by Redstart at 5:26 PM on October 16