Bat House Forum

[garverm]

Building my first bat house out of exterior grade 3/4" plywood that was left over from a project. I can make either a 36" high x 24" wide, 3-chamber house, or a 24" high x 24" wide, 5-chamber house. This will be mounted on an utility pole at the south end of my northern Indiana home, approximately 15' off the ground using lag bolts.

Based on experience, which of the two designs would you consider better from the point of attracting and holding a large colony of little brown or big brown bats?

[cloudman75]

Hello,
What are you using for baffles? Depending on how thick they are the 36x 24 will weigh around 80 lbs or more.
It will be a handfull to mount for sure. I just took down my 5 chamber 1/2 inch 36x 24 plywood house this week and replaced it with a three chamber about the same size of cedar. I won't be using plywood again as it is too heavy.
Here is my experience:
The bats used about half of the house and I had a colony of 100 mothers and 100 pups in it maximum. Most were little browns. The house was up for five years and successful I think. I had two other houses for them to use in cooler weather.
They would not use the house until warmer weather as I think the large space was too much for their body heat to keep the pups warm. The house was faced due south for a time and due north for a time. When it faced due north, the sun covered the back of the house and heated that chamber. It made no difference to the bats as they still waited for warmer weather to use it.
I am in North Georgia near Atlanta.
Based on my experience, I will never build another five chamber, but have decided 3 chamber houses are ideal .
The 36 inch height I think is good to let the bats go up for more heat and down for less. 24 inch height may be marginal as it is closer to the entrance. 14 to 16 inch minimum width is OK I think.
Based on my experience, rather than one large 5 chamber, I would build two smaller houses and mount them both on that pole you mentioned.
I hope someone else will respond that is closer to your area. I am just passing on my experience as we have the same bats here that you do in Indiana. Good luck and let us know what you decide. Please post some photos when you get it in place.

Frank

[garverm]

Frank, I appreciate your insights. Regarding my choice of materials for the baffles, I had planned on using the 3/4" exterior grade plywood. My secondary reason for this was my hopes that the thicker plywood would resist warping. My first reason for the thicker baffles is that this is the material that I currently have on hand. One additional thought, I read that some people have thought thicker wood offers better heat retention overnight, and buffers against high heat during the day.

It is interesting that you suggest the two smaller houses. A lot of the Bat House Research suggests building as tall and as wide as possible. They also suggest that bat house temperature is very significant. Your climate is certainly warmer than mine. My Spring weather can bring daytime highs from low 40's to low 70's, with nighttime lows in the upper 20's to low 40's. My summer temperatures this year had a lot of 90 degree days, where an open air digital thermometer on the back of the utility pole that I've mentioned would hit 110 degrees. This seems to indicate the south side of my home generates a lot of heat in close proximity to the utility pole. Since my utility pole gets 16 to 18 hours of sunlight per day in the summer, there is a lot of opportunity for heat build up. The use of two bat houses seems a better solution to offering a warm spring home and also a summer home that does not overheat. I could use a south-facing black, 3-chamber, home with no vents and air-tight Great Foam spray insulation for the warmer house. A dark brown home with vents could be faced east for a cooler home. I have had big brown bats (bachelors) behind the shutters on the north end of my home. They would seem to appreciate less heat. A possible project for the future might be running an electrical cord up the pole and adding a little extra heat to the house when outdoor temperatures are low.

My hopes were to get a nursery house going with lots of bats. Once I establish a resident bat population, there are several ideas that I would like to test regarding bat housing.

Thanks,
Matt

[cloudman75]

Matt,
If you want to see my five chamber with bats this year look under photos on this forum "relocated bat houses being used." They moved into the 5 chamber about june when temps were in the mid 90s . Look under "too hot for bats today" to see bats completely out of the house on the landing board.
They had also used my three chamber and another unvented house until it got too hot. In general my bats got way too hot this year in unpainted and also houses painted a light blue. Take a look at some of my posts if you want to see some bats hanging out because they are so hot. I built a big three chamber and put it up this week
to replace the 5 chamber. It is well ventilated, not built tight for a summer house. I have a new three chamber smaller house that is tighter for spring use. I have a tight darker colored blue house for winter. I had a few bats here in winter on warm days. I posted some photos of freetail bats that stopped by during the winter this year.
I still have about 25 or more little browns plus about 20 or so freetails as of tonight. I take photos of the houses right before they exit. If you have a black colored house, it will be too hot when temps in Indiana get in the 90s.
That's why I think several colors and several houses for different temperatures during the year would better serve the bats. My houses this year were full of bats,but at different times. Sometimes a particular house would not be used until the temp. suited the bats. I, and no one else in my opinion has all the answers on bats.
I do find it enjoyable to experiment with houses to see what the bats will do. I give them a choice for spring, summer and cold temps by providing several house types. One final comment, it took years for me to get 200 bats. I started with a small colony of 17 bats. After years of the bats having one pup each and most returning, I am up to about 200 after they have pups. It seems that only about 100 come back pregnant looking for a place to raise pups. Some are born males and I suppose some don't survive the first year hibernation. Start smaller with a number of houses would be my advice based on my experience. Even if you build the 5 chamber, add another smaller three chamber.
I will be anxious to see what you do and how the bats react.

Frank

[garverm]

Wow! Four sheets of 3/4" exterior plywood for a 3-chamber, 36" high x 24" wide nursery weigh a 'ton'. Last couple days, I have had 35-45 mph wind gusts. Really starting to re-think material choices.

[Terry Lobdell]

I think either size would be good, but I would build it in sections or componants and carry each piece up at a time.........I have pictures on here of one I built that way..........it weighs about 100 lbs......it was real easy to partially build on the ground then carry the 8 pieces up and attach to the pole one at a time........I know plan on building all my large bat boxes this way..