Friday, 2 January 2015

Bat in the House?

Big Brown hanging on a screen.  Note the blue tag.
My number is on the Web as a bat rehabilitator & I've been fielding a lot of calls about bat sitings this year.  This blog will be devoted to bat stuff...including some general information about WHAT TO DO if you find a bat in the house.
First...every bat that I've received from somebody over the fall or winter has been a Big Brown Bat (Eptesicus fuscus).  They are little, as far as animals go, but they're the 2nd biggest bat species in Canada and the only one that'll hibernate in your house

Big Brown Bat...note the bare nose.
during the winter.  The picture below shows the characteristic bald patch around the eyes and nose.  They have a puffy, hairless nose, unlike some of the other bats that might nose about your place in the spring and summer. 
I'll focus on Big Browns for this blog, as they're the ones you'll most likely encounter.
By hibernation time, BB's have reached adult size (thumb-sized body & wingspan of about 30 cm).  In order to survive the rigours of hibernation, a bat needs to be FAT and relatively undisturbed. Low body mass and disturbances mean they must awaken & move about and in the process burn precious fuel.  It's tough to know whether a bat is at a healthy weight without checking...some of the bats I receive are perfectly healthy & are released, while others are underweight and unlikely to make it 'til spring.
So, you have a bat in your house...
Baby Little Brown Bat
If it's early spring or summer, it could mean that a bat (or bats) are using your house to set up a maternity colony.  Females use the warmth of the attic (often) to speed up gestation.  These colonies can be big, with several hundred females, or small.  A quick scan for bat droppings or activity in the attic may reveal such a colony.  They're often noisy...especially once the young are born....and can be smelly, depending on the population size.  I've been knee-deep in bat guano in some attics...and even have some bat-urine stalactites from one house.  Anyway...I'll add an article that I wrote called, 'The Bats Are Back,'  in case you need more info on how (or if!) you want to deal with a maternity colony.
Once the bat pups have been weaned and they're flying and feeding on their own, the next big job is to fatten up for winter.  To do this the females (and young-of-the-year = YOY) abandon the attics (too warm!) and seek daytime lodging somewhere cool.  This enables them enter torpor (slows metabolism) and conserve energy and thus increase their body mass in prep for hibernation.  People with obvious maternity colonies often notice that things get quiet OR that bats start to move down in to the walls, and sometimes show up in basements later in the summer.   Young bats make lots of 'mistakes' when they first learn to fly and will show up in all kinds of awkward places at this time. 
BB's hibernating in a cave
Now it's time to hibernate.  All bats in Canada are insectivorous (Lots of bats arrive in a box with banana slices and peeled grapes.  I blame Stellaluna!) so when the insects are done bats either migrate south (some species never hibernate) or find a spot to hibernate.  The perfect spot is cool (just above freezing), humid, dark and quiet.  Caves and mines can provide this, but BB's will sometimes find what they need inside your house. 
Most houses are porous to bats at some level, but not all houses are suitable for a bat to make it through 'til spring - hence the mid-winter visits.  Imagine that a bat has moved into your house.  Insulation keeps heat in so outside of the insulation - but still inside the shell of your house - may provide lots of suitable places to hibernate.  Attics are typically too cold - unless the winter is mild or you have poor insulation - and too dry But, somewhere between the roof line and the basement there could be suitable conditions.  Homeowners can sometimes hear bats (mice? rats?) moving up and down inside the walls during the winter. Once a suitable location has been found the bat drops its temperature and begins to hibernate.  There are, however, several things that can wake them from their sleep:
DISTURBANCE:  I get a lot of calls around Christmas and other holidays when people are home, hiding presents in weird places, snooping around in attics, turning up the heat for gramma, etc...
BODY CONDITION:  Mortality in the YOY is generally high.  They may have had only a few months to fatten up, so they get hungry and must come out of hibernation to find food...of which there is none.  I get lots of emaciated bats in Jan. to March, before insects are abundant again.  Old bats will also expire at some time.  It's hard to tell the age of a bat except for in the 2 or 3 months after they are born.  Disease (e.g. White-nose Syndrome) can also deplete their reserves as they sleep, essentially starving them).
WEATHER:  Most of my calls pour in after a dramatic change in the weather.  A cold snap means bats may have to move closer to the warmth in your house.  A warm spell means they have to move away from the heat.  Listen for noises in your house after such changes.  The fall and early winter of 2014 has been reasonably mild and I've had many calls from people finding bats on their house, under their decks, etc.  Ambient temperatures were just about perfect for hibernating outside.  It's important to realize that bats don't necessarily sleep  peacefully from autumn until spring...they must move when needed to maintain the right environment.  I've seen one flying down Frontenac St. in Kingston in the midst of a snowstorm.
So, What do I do if I find a bat in the house?
If it's summer time, see the article on bat relocation in 'The Bats are Back' (next blog).
In the winter...
First, don't be surprised if it can't fly.  If a bat gets into your living space and has time to just hang out it will eventually lower it's body temperature to that of the room - say 20 C or so.  At this temp. it physically cannot fly.  It'll still be responsive and may hiss and bare its teeth (impressive!)& it may even stretch its wings, but it cannot fly.  In order to do so it will have to warm itself up to about 37 C which it does by shivering.  If you disturb it and then watch, it'll start to shiver slowly at first and then violently until it gets warm enough.  This might take 15 minutes or more, and then it'll get what I call the "launch Look" during which it blasts out sonar calls and THEN it will fly.  Before it warms up you can CAREFULLY wrap it in a dish towel or grip it gently with heavy gloves and place it outside...even if it's cold.  Place its belly against a tree or a brick building.  Be sure that it can cling to the surface and make sure it's inconspicuous to protect it from cats, birds, etc.   If it's daylight, the bat might stay until dusk, but when it warms itself up it will likely go back to where it came from...likely back into your house.  I'll be unlikely to make the same mistake twice.  If, however, the bat stays where you placed it for over a day, it may need more attention.
Hanging High on the Christmas!
If it doesn't fly after a day or so...or if it shows signs if injury (blood, tears in the wing / tail, bones at odd angles or asymmetry in the way it hangs), it will need help.  A 'normal' looking bat could be underweight for a variety of reasons (see above) and will need help.  Contact your local wildlife rehabilitation centre to see if they work with bats.  Bats are considered a 'rabies vector species,'  so not all centres will be able to receive them.  In most cases, you'll have to deliver the bat to the centre, unless some other arrangements can be made.  Some have 'flying angels', people who volunteer to bring injured animals to a care facility.  KEEP THE BAT IN A COOL, DARK, QUIET place if you've decided to take it somewhere.  I transport bats in small, cotton pouches that are tied at the top (similar to a small pillow case) but a cardboard box with a tight fitting lid and some fabric onto which it can cling or under which it can hide will serve.  Do not attempt to feed the bat (see the red bits below!).  You can put in a small water dish, but it is unlikely that it will drink on its own.
If it's flying normally you can wait for it to settle...they often land high, on curtain rods, etc. when given a chance and then follow the directions above OR open several windows, a door, etc. and hold up a towel (a soft, sonic and visible barrier) as it flies by to direct it towards the opening.  This can be fun.  Most common 'mistake' is to see a bat flying and to leave the room.  You might spend weeks not knowing where it is, or if it has left.  People often claim that a bat is diving or swooping at them in the room, but if you sit near the wall and stay low, you'll see that it will fly up near the walls, touch-n-go with its belly and claws (and perhaps hang) and then, to get flight speed it must 'swoop' at the centre of the room before another wall looms.  BB's are nimble, fast flyers and will have trouble making turns in a small room.  You could use this to your advantage.  Keep pets out of the room!
In every case, make sure that you don't get bitten!
That's a whole different in which the local health unit must be notified, the bat must be killed (even if it's can only tell by removing its brain...bats don't survive a rabies test) and you'll have to have post-exposure shots until the word gets back on the bat  DONT put yourself in a position where you could be BITTEN!  Got it?


  1. Thanks for the info. I look forward to seeing and learning more. Can you add a "Follow" or Subscribe link so I don't miss any posts? Thank you!

  2. Thank you for posting this! It is by far the most detailed (and practical) info I've found online about what to do when you find a bat. I will definitely be following your blog & can't wait to read more! Thanks!

  3. This is a great post! Thank you.
    I grew up in Kingston area and have been around these awesome little creatures for decades. In Ottawa, our house has had a bat or two flying through it every summer for 25 years. Never found a colony but only once when renovating found a few climbing the walls in an addition. I have helped neighbors over the years remove bats from their homes deploying the methods you described (I learned them myself over the years from trial and error). One I plucked off a wall carpet by pinning his wings and carrying him outside. I have only ever lost one bat and that was through the panic of someone else trying to catch it.
    Today I removed one from a neighbors house and released it outside. It seemed quite healthy and looked like a mature bat. He immediately made a beeline for the wall next to the porch, but I don't have a lot of hope this one will survive.

  4. Thank you for putting this information up! Found a bat on the snowy ground and carefully captured in a fabric bag - my knitting bag! - but what can you do? - and kept small visitor overnight in quiet dark box with holes in lid and a towel. At next dusk released at a tree with best wishes. It didn't seem injured, hope it survives. Your winter rescue info very helpful, thank you.