Bat House Forum

[lakefly]

    We have had bat colonies (2 in seperate wall areas) for the last 20 years.  These colonies have thrived and grown to an undetermined but very large number of bats.  This year for the first time we are seeing many dying bats - mainly young pups but also mature bats.

Do you have any ideas of what may be causing the deaths?  We are assuming that it may be overpopulation but also have concerns about disease.

[Terry Lobdell]

Where are you located and where are you finding the dead bats?

[lakefly]

I live in southeastern Wisconsin.  The dead bats are directly under the soffit of the house that they live in.  I have been finding a few dead bats each day.  On the opposite side of the house we have another colony but no dead bats on that side.  Is it possible that the deaths are caused by over-population?

[kent borcherding]

A bit of a puzzling problem.

Some questions have you been doing any outdoor burning, such as a campfire or a firepit fire where the smoke may have drifted and caused the bats deaths ? Smoke will kill bats very quickly.

Also has anyone sprayed a farm field , lawn or roadside nearby possibly wind may have blown the spray onto the bats or into the bat roost ?

Has any work been done in area where the bats may have night roosted ?

Possibly paint spraying , or any costruction sites where they may have sprayed cocrete sealer on concrete walls? Bats clean and preen themselves and if any spray or sealer is on the bats the bats will ingest and cause sickness or worse death to the bats.

I live south in Hazel Green , Wi. you are welcome to send me a private message and I will give you my phone number.

[lakefly]

    The answer to all of the questions is no.  Wwe have not changed anything that would impact the bats nor have there been any fires, etc.  I still wonder if it is possible to have an over-population issue.  We have SO many bats and have not done anything to discourage them from sharing our home.  It is also strange that it is only on one side of the house that the dead bats are appearing.

[kent borcherding]

Another questions ?

If you have a gas water heater or gas dryer where do the fumes vent to ?

Has anything changed that could possibly be causing a down draft from where any gas appliances are vented ?

Next question are there any flooded fields nearby where the bats could be skimming the surface to drink ?

This standing water could possibly be contaminated with crop spray ?

The night temps have not been cool enough to keep the insects from flying .so that bats aren't starving.

Bats increase by the food supply and colonial bats feed in approx. 6 mile area. Overpopulation should not be causing the problem.

What concerns me is had a phone call earlier today where bats are being found dead and sick in another area of southern Wisc. I will be going to visit that site soon.

[lakefly]

    If you have a gas water heater or gas dryer where do the fumes vent to ? In an entirely different area from the bats.

Has anything changed that could possibly be causing a down draft from where any gas appliances are vented ? Nope

Next question are there any flooded fields nearby where the bats could be skimming the surface to drink ?  No, we live on a large lake and have not had contamination issues.  Also, the colony on the other side of the house has not been effected.

This standing water could possibly be contaminated with crop spray ?  Doubtful as this area is residential.  

I think I will get into the attic area to see if I can see anything out of the ordinary in that area.

The most curious thing is that only the one colony seems to be effected.

[IowaNate]

 Definately a difficult situation to figure out. I have had 8 dead bats this year due to what I suspect is overcrowding in my largest bat houses. Perhaps a bat house close be might be in order to relieve some of the stress if they are overcrowded. I never had a serious problem with dead bats untill one of my houses had bats almost falling out of the bottom since it was so heavily occupied. But this is the first year this has happened in over 11 years at this site. Then again the floods here in Cedar Rapids have contaminated the water supply to a certain degree...I hope that the bats dying in the Midwest are just a coincidence and not a sign of a larger problem the same as or related to White Nose Syndrome. Let's keep our eyes open and make sure we see the signs of a much larger problem if it exists. I for one am starting to get a bit worried.

[lakefly]

I am being very watchful also.  No dead bats this morning! 

[lakefly]

    This morning I found seven dead bats and two more dying.  I spoke with the  local DNR and other agencies and gathered the bats, froze them and will deliver them to their offices this morning.  They will process tests and get back to me with results - some concern about white nose syndrome.
I will keep you informed of results and it would be helpful to know if anyone else if having similar issues.

Thanks

[Joe Spencer]

Looking forward to the DNR information.  Maybe they will have some answers for you.  With the abundance of local water and summer conditions providing numerous insects this is indeed a puzzling situation.  Either way a large bat house or multiple bat houses should be considered if at all possible as mentioned.  Have you ever considered excluding them?  Nice to know you have been living in harmony with them. 

[lakefly]

    We have considered excluding them in the fall after the pups are grown but our house is large with many bat options for access. It is a rather overwhelming task to make sure that we do not just move them to another location in the house.
We have tried bat houses but not successfully. 

We have lived in harmony with the bats and it has been a great experience for our children and now grandchildren, friends, etc.  It certainly demystifies the bats and helps people appreciate their benefits.  Most people think we are nuts to not exclude them and are "freaked" by their presence until they observe them for a short time.

Incidentally, we now have deaths in both colonies on the north and south sides of the house.  I had previously not seen any dead or dying bats on the South but found three yesterday.

I am anxiously awaiting the DNR information.  Where there are no characteristic white markings on the bats but they are very dehydrated and weak when they fall from their roost and die within a short period after dropping.  For anyone that watches this phenomenon it is heartbreaking to see them dying and yet unable to help them.  They are watchful in this state but never aggressive. 

Is anyone else seeing this in their bats???

[Terry Lobdell]

Here in NW PA I have observed  a fairly good sized increase in 3 of my little brown bat colonies at different locations. The only dead bats I've found were fallen pups from overcrowded bat houses. What kind of bats are living in your walls?

[lakefly]

    Little brown bats.

[Joe Spencer]

Lakefly,  what has been the average daily high temp for the last week or two at your location or during the times when you found the most dead bats?

Does the home have a black or very dark shingled roof?

Has it been sunny or overcast during these days?

Have you noticed increased bat activity near the soffits (lowest and coolest point) during the warmest time of the day?  It may be too warm for the bats although little browns do have a higher heat tolerance than other common species.


Joe