Bat House Forum

[IowaNate]

  The house on the right is currently being used by 9 big brown bats. Both houses are 12" wide and 24" tall with three chambers. 8 of the big browns are in the rear chamber closest to the house while the 9th is in the front chamber. As you can see, the house is mounted about 4 feet above my side door awning but doesn't seem to affect them in any way. From the ground, both houses are 14 feet up. They get about 6 to 7 hours of direct sunlight untill the tree shades them lightly in the late afternoon. And these houses actually face North, I saw no problem with this since they get good sun and there had been bats roosting in the gable vents above the window. Current air temperatures are in the mid 40's for highs with high temps forcasted being in the low 30's next week. If they are still occupying the house by next weekend, I am hoping they will hibernate.

     Even though there are many little browns bats in the area, they have never used these houses during the 5 years they have been up. But the first big brown moved in within one week of hanging. The numbers have always been 1 to 3 bats per house with the exception of this Fall.

[IowaNate]

A few close up shots of the occupied house which is starting to show signs of wear. The plywood is starting to separate in a few spots, but I believe that the bat house gets much of it's thermal stability due to being mounted on my home, despite a few small air leaks in the bat house itself.

 

[Terry Lobdell]

Nate, have you considered covering these bat houses with metal to make them last longer?

It is interesting that you only have big browns use these houses. I have houses mounted on both poles and buildings and the big browns strongly prefer those houses mounted on buildings.

[IowaNate]

 I am considering experimenting with metal. Although I must say that the exterior of these houses is just 1/4" plywood (I was going for light weight) and this is thier 5th year exposed to the elements and facing North. A lightweight metal flashing painted brown might be just the thing to keep my houses lasting 20 years or more.

[IowaNate]

 It snowed 2.5" here last night. Temperatures are in the low 30's for highs and in the upper teens for lows. I do believe my big browns are staying in the bat house for winter. There is no sign of temps getting above 45 for the next week or so.

   I will only be using my infrared camera to check on the bats about once a week to keep from disturbing them.

[Terry Lobdell]

I had 2 big browns roosting last week........I think it was Nov. 13th..........I am going to check again tonight.........last year Nov. 28th was the latest I observed them roosting.......I guy near Lake Erie has a barn with a colony of big browns told me he has seen them flying around inside on mild days in Jan. & Feb.

[Joe Spencer]

Very nice photos.  Thanks for the information Nate.  Once I had two consecutive nights below freezing this year, my last Big Brown Bat left for hibernation.  Big Browns do not migrate/travel and hibernate nearly as far as little brown bats do.  I would be surprised if your bats stayed in your houses all winter in Iowa considering its latitude and reasonably cold winters so you feedback on occupancy would be helpful.  Gosh it snowed in Texas too yesterday.  Are you reasonably close to the Cedar river or some other major water source?
 

[IowaNate]

 Joe, I am located about 3/4 mile from the Cedar River, but there is a spring fed stream about 300 to 400 yards away from these houses. The width of the stream is 15 feet on average.

[IowaNate]

 It seems as though my big browns are indeed hibernating. Temperature has been in the upper 20's and lower 30's for highs, and all 9 bats are still in the house. As I did further research, I noticed that the sunlight barely touches these houses this time of the year. I never really checked my houses and the sunlight they received in the winter, untill I heard some chattering in the house in late October. I think the lack of direct sunlight is key to the bat's hibernation, if the house were in the sun, they would get into the upper 40's and perhaps 50's causing the bats to awaken.

  Has anyone else had hibernating bats in thier bat houses on this forum?

[Terry Lobdell]

Nate, I've never had hibernating bats in any of my houses. I just went out and checked tonight and all my houses were empty. I did have 2 big browns roosting Nov. 13th. Last year Nov. 28th was the latest I observed them roosting.

Seems like I have read somewhere that they've been known to hibernate in bat houses. What species and where, I do not remember.

[kent borcherding]

Big browns have been known to hibernate in buildings that are dry in below freezing temps.

Studies have not been able to determine if the bats body temp falls below freezing.

I have had a few big browns in bat houses in northern IL. in Nov. but then they moved to a cave hibernaculm.

Usually bats that hibernate in attics or mainly walls of rock or brick buildings in the northern climates arouse in January to drink.



This is why most bats prefer mines and caves because temps are stable above freezing and high humidity.

Bats will lower their body temp to just below surrounding temps and condensate will cover their body and satisfy the bats moisture requirements.

[IowaNate]

 Thanks Kent for some insite. I know that they have hibernated in my next door nieghbor's attic in the past few years, but I never expected them to stay in one of my bat houses this late in the season and with such low temperature.

[IowaNate]

 The bats have left. I checked them on Friday, November 30th, and all 9 were still in the house. We had a major icestorm this weekend, and the temperature has dipped into the single digits at night. I checked all three bat houses mounted on my home, and all are empty. I hope all of them make it through the winter, and return to the bat houses in mid April as they have done before.

[Terry Lobdell]

Nate, I had a big brown roosting in one of my east facing houses 3/22/07.

My big browns appear to come back a little earlier than my little browns.