Bat House Forum

[southTXheat]

We have a ranch in south Texas close to Mexico border. Next to our main houses is a large pump house and tool shed. There is a large colony of bats that have been roosting above the pump house for several years. The colony is easily several hundred. I do not think the bats migrate since winters are typically mild and summer temps are over 100 degrees. No telling how much guano has built up over the years but the smell is very strong.

We need to rebuild the roof of the pump house and most of the bat houses I have seen do not look like they will house that many bats. How many bats does a typical bat house hold? Plus our goal would be to move the colony further from our main houses and closer to the nearby cattle tank so pratical suggestions would be helpful.

[William Bagwell]

This thread from from back in July has a couple of formulas for estimating capacity.
estimating-bat-house-capacity-t862.html?hilit=Capacity#p4504
I think it is mainly for little browns so you may need to adjust according to what species you have.

William

[cloudman75]

Hello in South Tex.
You may need around three or more houses. I believe your bats will turn out to be identified as mexican freetails. They are about the same size as little browns, and I have had some here roosting with my little browns in Georgia.

Here is a plan that they say is good for 250 bats max so thought that you might look it over. Your bats will not want to move so you will have to exclude them if possible after you get some bat houses up on poles about 20 ft high or at least 16 ft. minimum. Take a look at the standard bat house plan from this link. I built one using 5 chambers and had about 200 bats in it that were not too crowded. The bats usually have one pup each summer so they will need room for them in addition to the adults. This is a very good plan, but heavy. You probably have a way of getting it up on a pole. Good luck and keep us posted please. Now is a great time to get the houses up. You could build one very large house if you can handle it. What ever you do don't paint it a dark color. White or light blue would be fine I think in your location. You don't need any black rolled roofing,etc. About any direction you face it would be OK as I doubt they will need a lot of sun at your place.
http://www.portal.state.pa.us/portal/se ... 397&mode=2

Frank

[southTXheat]

Thank you for the responses. I hope to get this done soon.

[cloudman75]

Using the formula I found which seems to be a little liberal, a 48 inch wide x36 inch high house with three chambers
would have a capacity:
48x36 = 1728 sq inches x .75 inch spacingx 3 chambers (2.25 in.) = 3888 cubic inches divided by 3 cubic inches per bat is
1296 bats. A more conservative number would be to give the bats 4 cubic inches each which would still be 972 bats.
You can shift the dimensions around on the link I sent to suit your likes and dislikes. The main thing to me was weight, but I'll bet you have a loader and tractor or backhoe on your ranch to handle anything you decide to build.

Good luck and be sure and keep us posted on how it all works out.

Frank

[Terry Lobdell]

I've done some experimenting with bat house capacity the last couple years and have come up with a conservative estimate of 15 mothers per square foot of roosting surface in order to not have pups falling to the ground.

I had a small box a few years ago with 77 little brown bat mothers right before they gave birth. The box only had about 3 square feet of roosting surface (assuming just one side within the baffle). I knew it would be too crowded and sure enough we had 5 pups fall and die even though we mounted a larger box close by.

That box had roughly 25 mothers per square foot of roosting surface. So based on that experience and others I feel the 15 mothers per square foot is a safe estimate.