Honeydog,
During winter, even one where folks in some areas area getting warm temps and no snow or little snow, etc... folks can be tempted to put bats outside when found inside.
It is possible if the weather is warm enough and the bat isn't fully in torpor that it will fly up and enter the house where it had in the first place to get back to the colony or
roost site within the exterior or attic.
I'd like to give you a hard and fast rule, but honestly the only actual guidelines I've seen discussed say the following:
"If no potential for rabies exposure has occurred and weather conditions are appropriate (above 50 degrees F, no rain or high winds), a bat found in a living space can be safely released outside"
That information is found within a few publications, but the most recent AMPs (Acceptable Management Practices) document includes it along with other info you might find helpful coming from a place of not having much experience in this arena versus folks who do various bat work as a main line.
Here is the link:
https://www.whitenosesyndrome.org/sites/default/files/resource/wns_nwco_amp_1_april_2015_0.pdfFrom winter through spring the last several years following our friend moving who was a local licensed rehabber of bats, we start getting them in from just after onset of freezing (no more insects, no food, so hibernate, migrate or die) through into spring.
Some years just a few but this year had 6 of one species from a large office building. Bats were in fine shape, but temps outside were well below freezing. Bats can and will fly in very cold temperatures, the question here is does releasing a bat found in the interior of a home during mid winter or extremely cold times give it a fair shake at making it, or should it be taken to a rehabber (if legal and possible in your area) where it can overwintered or if need be euthanized if injured severely.
No clear answer on that, we overwinter everything we get but we have all the various pieces of the puzzle from legal through pre exposure shots and some basic training in this realm along with some advanced and some excellent colleagues to pull info from.
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So on to your second question, why all the same day? Ask them if they did something or had something done to the home in terms of any light construction, repair, etc... Not always the case, quite often it seems just related to moving to a temp or airflow or other aspect they can sense while in the roost, say it gets really cold and the space they are in doesn't seem sufficient to weather it out, they can shift or move within the roost and that may lead them to pop out indoors and in multiples. The 6 we picked up recently all came out within 3-5 total days, basically 2 a day with a couple getting off somewhere or back in the ceiling/walls where they weren't found and maybe back in the larger colony overwintering there.
I have a client that we did some basic exterior exclusion for night roosting bats, didn't request or have any issues with bats in the home. He just had a guy do some pack rat extermination for him and tells me he had 2 bats in 3 days last week show up inside and wondered what my thoughts were on why?
Asked if the rat trapper plugged any holes on the exterior of the porch near the ceiling? "Yes he sure did" There you go, blocked the bats in, changed the airflow, temp or conditions and the bats which he'd never had inside his home were now inside as they only had one way to go.
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Anyway, if you have a licensed rehabber in your area, that would be the easiest deal to work out for the cases where you get them from homes. Just my opinion though, obviously folks do a wide array of things an will therefore have a wide opinion range, check legalities as well, though typically single to several bats inside a dwelling is open to suggestion due to various reasons.
Just my .02
Justin
