Bat House Forum

[Joe Spencer]

Terry, thanks for your feedback on this.  As we know, the bats can only lower their body temperature to  the lowest of their surroundings until it is too cold at which time they then must resort to raising it.  If we have a stretch of cold early spring sunny weather in which a bat house may heat up far greater than the outside ambient temperature, the bats then have their body temperature, heart rate and metabolism raised and subsequently burn precious fat.  Unfortunately there are no insects active on these evenings during this type of weather.  It is most critical at this stage since the bats have nearly exhausted most of their fat during hibernation.  I had a couple bat houses mounted on my home a few years ago which got some good southern exposure.  One nursery house had reflective foam insulation in the front chamber and the other bat house on the other side of the window did not.  This was my second season with these houses in which the bats had arrived quite early in April but they spent most of April in the insulated house during cool sunny weather and switched to the other bat house mounted on the other side of the window as April turned to May during warmup.  By this time they were feeding somewhat regularly and guano was accumulating.  In summary, a consistently warmed bat house during consistently cool outside temperatures without insect activity may not be inviting to bats especially male bats.

[IowaNate]

 It reached into the mid 70's today and I noticed the six big browns in the Northwest house were roosting very low next to the side vents. This was mid-afternoon when the house is mostly shaded.

[IowaNate]

 A little better photo showing four big brown faces in my NW house.

[IowaNate]

  It's 8:30 pm and 5 of the 7 big browns have left the houses for the night, and the other two are very awake and near the bottom of the house. I am anxious to check my hybrid house in the morning since this is the first time I have actually seen them leaving the houses this year. The outdoor temperature is currently 68.7 degrees.

[Terry Lobdell]

Nice pictures Nate! That warmer weather is headed my way. Still a little cool here in PA, low 40's. I work 2nd shift most of the time but am off on Friday so I may be able to do an exit count.

[IowaNate]

  Since the bats left the houses last night, I had 6 return. 4 of them are in the NW house, and the other 2 are behind the attic vent louvers roosting on the screen on the North and South side of my home. These bats are moving around alot from roost to roost it seems.

[IowaNate]

 As of April 25th, all of my big browns have left the bat houses. Although there are still two big browns that are using the screen behind my attic louvers almost everyday.

  There has been no use of the new slanted baffle/standard hybrid house, but I will leave it hang through May of 2009, and if it hasn't had any occupants by then I am going to relocate it.

[Terry Lobdell]

I did an exit count of my big browns roosting on my house last night. I had 7 in one box and 8 in another......Looks like this will be the 4th year in a row that I've had around 15 big brown mothers. Since last year they seem to be splitting up more often.

My little brown maternity never does this..........the mothers always roost together in one box.

[IowaNate]

 Terry, I believe that big browns might not roost in larger nursery numbers due to the fact that they like slightly cooler temperatures than little browns...so there isn't as much need to share body heat among each other. Whereas the little brown nursery colonies usually have many bats roosting tightly together.

 I have come to agree with Kent on the usage of the houses mounted on my home in that they are mostly used as "transitional" houses during fall and spring. Granted I usually have one or two big browns stick around throughout the summer, but the major usage during late fall and early spring has me thinking that I might not ever have a nursery colony. I will give them one more spring to see if they use the larger hybrid house, and if they don't I will just stick with the two most occupied houses with the bachelors and relocate the other two.

[Terry Lobdell]

Nate, that makes sense about big browns roosting in smaller numbers due lower temp requirements........Sometimes they do all roost together though........maybe I will pay closer attention to how weather conditions correlate with their roosting patterns. 

[Terry Lobdell]

Just got in from checking my big brown maternity........all 15 mothers are roosting together in an east facing box.......Two nights ago they were split up in 2 other boxes........I did not check them last night.............but judging from guano they were probably in the same box as tonight.....

[IowaNate]

 Here it is in the heat of summer and I still have one big brown in my attic vent and one moved back into my SE bat house. The one in the bat house has been back there for at least a few days judging from the guano accumulation. But still none using the slanted baffle house.