Bats - your most effective insect control

Dave Bennett wrote:
I wish I could get a reasonable count of just one slot of one of my bat houses.  Then I could make a good estimate as to the size of my "neighbors."  My bat houses are a bit larger than the standard plans available all over the "net" because I wanted more bats in the neighborhood.  There is a huge drainage "pond" at the end of the street so the mosquito population was huge when I moved here 17 years ago.  Now it is much better.

If the house is packed to the gills, you can do an exit count.  Otherwise you can take a flash photo looking up into the house and count the bats in the photo.  But you have to orient the camera in a certain way in order for that to work.  Let me know and I'll post the procedure.

An interesting design aspect I have found is what I call for my lack of better terms the "igloo effect".  Essentially, because air heated by the ground and the bats rises, there should be a steep step or slope from the ceiling of the entrance to trap the warm air.  Also the slop prevents water traveling in the cave as long as it is above the flood plane.  I did a brief drawing to show how this works.  I presume that the bats can hibernate at least in a  comfortable 70 degrees since the ground here is typically at mid 60s degrees Fahrenheit.  The earth/concrete is not a good insulator but it is a good conductor of heat from the ground.  Please do not look at this drawing for dimensions, its a show for concept.  I would prefer 12ft ceilings to 3ft ones.

adunca wrote:
Actually the first bats in the US with White-nose Syndrome were in a cave in New York:

Here is a paper on bat hibernation in New York: http://www.oneonta.edu/academics/biofld/PUBS/OP/Hibernating%20Bat%20Populations%20in%20Eastern%20New%20York%20State%20OP%2014.pdf

Well actually there are caves in NY just not anywhere around where I grew up.  I did not say that there weren't any caves I said there aren't any around where I grew up.  Big difference.  I just read some of that study Schoharie, Albany, Montgomery counties is where the study was conducted.  One hundred + miles away and more towards the north from where I lived but I did notice that the map of the suspected transmission path passes through where I grew up.

No need to get feisty, you both are right.  A cave is not essential, more ideal for hibernating bats.  I imagine bats have found homes in many areas but also consider that it does not ensure their survival.  A residence such as a cave is ideal, but not the only solution.  There is a reason that bats gravitate towards caves.  You have to consider that it is at cool temperatures during the hot summers and more importantly warm in the winter months.  The geothermal energy is much to thank for this. 

I've used roofing tar paper (black stuff) loosely wrapped around a tree trunk (about 6' up) that's exposed to the sun - especially in winter.  They are loaded with bats... they can control their temperature by rotating around in there.

I was playing around with an idea for a mini "bat cave" concept today.  Nothing on paper just an imaginary vision while I consider the possibilities of providing thermal safety yet light enough in weight to allow them to be placed in areas with sources of food and water.  Multiple bat caves.  Much like purple martin "hotels" but built for bats.

I want to make sure that people understand a couple of things.

1. Bats are very selective about their roosts, especially with regard to temperature.
2. Males have different temperature requirements than females.  Females need roosts that are usually 80-90 degrees, for giving birth and raising pups.  Males prefer roosts that are a bit cooler.
3. For bats that go into torpor/hibernation in the winter, humidity is also a very important factor in selecting a hibernation site.
4. Different bat species form different sized colonies.  e.g. where I live it is better to provide a lot of smaller roosts vs. one big roost, because our bats do not form really large colonies.
5. Bats change roosts (and move around within a roost) frequently.

Here are maps showing the ranges of non-hibernating (left) and hibernating (right) bats:

(from http://www.fort.usgs.gov/wns/)

In the summer, bats that use caves/mines for summer roosts usually use the warmer parts of the cave.

In the winter, bats who hibernate use the parts of caves and mines that have cool, stable temperatures and high, stable humidity.  They will travel long distances (hundreds of miles) to reach these very special places.

So if you were to build a "bat cave" that you wanted bats to use year round (assuming your bats hibernate), you would need to design both a "summer zone" and a "winter zone".  And there is no guarantee that bats would use either.

In the wild, most bats use large caves or large hollow trees in the winter, and in the summer they use large dead trees/branches with exfoliating bark (they crawl up under the bark), or rock crevices, or warmer parts of caves.  So in the summer bats are looking for anything that is like exfoliating bark, a large tree cavity, a rock crevice, or a cave opening - which means they end up under loose siding, in louvered attic vents, under loose roofing shingles, inside chimneys, inside folded pool umbrellas, in attics, in belfries (of course!), in crevices at the bottom of bridges, under black tarpaper that people have wrapped around trees (), etc.  Oh and of course in bat houses, which simulate exfoliating bark.

So, here is what I would do:

1. Walk around your property/neighborhood just after sunset, on a night with a lot of flying insects, to see if there are any bats in the area.  If there are not, then your chances of attracting a colony are slim.  However it is still worth trying to provide at least a little bat roosting space.
2. If you have any of the roosting spots I mentioned above on your property, observe them carefully to see if they are already being used by bats.  Look for droppings below the roosting site/entrance.  They look like mouse droppings but they are very light and crumbly (they are made from insect skeletons).  There may also be some staining from body oils or urine.
Here are the droppings of Big Brown and Little Brown bats, our most common species:

(from http://bathouseforum.org/forum/small-grey-looking-bats-t764.html)
3. Most bats will not roost more than 1/2 mile from open water.  They must drink while flying, so they need open water that is at least as big as a bathtub.  If you have no open water nearby, your chances of attracting a colony are slim.  Or you could put in a pond (or stock tank filled to the brim).  They do also drink from swimming pools, although the chemicals are not too good for them.  In fact if you live in the desert, you absolutely should put in a pond or tank for bats to use.
4. So if you have seen bats and there is water nearby, your chances of attracting a colony are good.  Study up on your local bats, read everything on BCI's website about bat houses (start here: http://www.batcon.org/index.php/get-involved/install-a-bat-house.html), and put up a bat house on a building or a pole.  Make sure to follow the coloring and placement guidelines from BCI.
5. Wait a couple of years to see if bats use your bat house.  A decent sized bat house can hold several hundred bats, which if you are in town is enough to provide bug control for your whole neighborhood.
6. Now, you can start thinking about your bat cave or giant bat house or whole series of bat houses (depending on the species in your area).  I would focus on providing summer roosting space.   I would guess that even if you could provide the exact conditions your bats need for hibernation, the chances they would choose to use your cave for hibernation (vs. all the other caves, mines and hollow trees within 200 miles) are slim.   If on the other hand your bats do not go into full hibernation but just go into torpor for periods of time, then there is a very good chance they will stay in your cave all winter.  e.g. I know of a few colonies around here that stay in attics through the winter.  But generally speaking you'll need to live somewhere with mild winters in order for that to happen.

I'll grant that this is an older book (1925), but worthy of a read if you are interested in bats:

http://www.soilandhealth.org/03sov/0302hsted/030212campbell/campbelltoc.htm

When building a batcave or a large bathouse, I think connecting a couple of baffles to the ceiling would help to reduce a cooling draft.

Historic bat house in my locale:  http://www.batcon.org/index.php/media-and-info/bats-archives.html?task=viewArticle&magArticleID=398



There's also the Old Tunnel "bat cave"

http://www.tpwd.state.tx.us/huntwild/hunt/wma/find_a_wma/list/?id=17

I'm in "bat central" here in Central Texas, but so far have not managed to put up any bat houses. 

I remember seeing that tower when I was "traveling" around Texas back in the early 70's "touristing." 

The house fell down? the original one because too many bats came into it. ? I wonder if you use cob you can make something like that with less cost? well place steel structure some cob and burring it? or hempcrete with a sealing on it?

Jordan Lowery wrote:

While many of you were watching the swarm of bats, and thinking of the millions of insects they would eat, I was trying to imagine how much bat guano must get deposited on the floor each season.  A true permaculture solution...convert too many insects into an extremely valuable natural fertilizer!

not only that, but most of these bats are eating insects outside of your property, so you get the benefits of large amounts of organic biomass coming from somewhere else. essentially bringing fertilizer to your land.

birds do the same thing but i bet bats can do it a million times better.

I get this same effect (import of nutrients) from the many hundreds of grackles and cowbirds that overnight in my bamboo groves. Their droppings fertilize the bamboo and spread out onto the adjacent land.

Just stumbling upon this old thread -- fascinating.

The original premise is that by attracting bats, you are eliminating insects that are otherwise harmful to your garden and crops. The primary insects that bring badness to my garden are: A) sow bugs/wood louse, B) slugs, and C) those little white butterflies that lay eggs on my cabbages which turn into worms that eat them. A bat wouldn't do anything to any of the three. The sow bugs are out there in the soil, and crawl up the plant to eat their lunch. Same with the slugs. The little white butterflies don't fly at night.

We don't have mosquitos here, so even that pest isn't a pest for us. In fact, there don't seem to be too many nocturnal insects here. You'll get some moths and june bugs in the summer, but that's about it.

So while I'd love to have the free bat poop to use in the garden, their insect eating wouldn't be that big of an asset for me where I live.

Marco Banks wrote:Just stumbling upon this old thread -- fascinating.

The original premise is that by attracting bats, you are eliminating insects that are otherwise harmful to your garden and crops. The primary insects that bring badness to my garden are: A) sow bugs/wood louse, B) slugs, and C) those little white butterflies that lay eggs on my cabbages which turn into worms that eat them. A bat wouldn't do anything to any of the three. The sow bugs are out there in the soil, and crawl up the plant to eat their lunch. Same with the slugs. The little white butterflies don't fly at night.

We don't have mosquitos here, so even that pest isn't a pest for us. In fact, there don't seem to be too many nocturnal insects here. You'll get some moths and june bugs in the summer, but that's about it.

So while I'd love to have the free bat poop to use in the garden, their insect eating wouldn't be that big of an asset for me where I live.

The easiest way to control the pests you've listed is to run free range chickens (and ducks if the slug component is significant) through your garden. There is some potential that they could do some damage to your crops but there a number of techniques you can use to minimize this. I have been running chickens and ducks in my vegetable garden for several years and the sow bug, slug, cricket, potato beetle, and other insect population are close to zero. Before that I used to have a lot of problems with small gray slugs in the cabbage and broccoli and crickets/grasshoppers were plentiful. They also seem to be fairly effective against cabbage white caterpillars since these mostly disappear from my plants once their damage to the leaves becomes visible. To control the cabbage white butterflies, I keep a butterfly net handy in the garden to use in snagging and killing any I see flying though the garden.

I've always wondered how effective bats are at controlling mosquitoes since bats do most of their hunting 10 to 50 feet above the ground in open areas, whereas mosquitoes are mostly found in and around vegetation near the ground where their warm blooded mammalian and roosting bird food sources are likely to be.

I have a redwood stump 15 foot thick at breast height (I did not cut it!) in my back yard with a hollow in the center about 4-7ft wide, and its probably 12ft tall. I have two other taller, more slender snags (8-10ft thick) as well but I think the hollow would be my best bat habitat. Would simply attaching a sheltered box in there suffice to attract roosting bats? Do you do anything to get them there in the first place, like tie a moth to a string attached to the box:)?  I have some around, and they do roost in the old growth tree hollows, but more would seem better. Also, would my great pyrenees-akbash that likes to hang out in there more than his house scare them away?

I don't know how many bats there are around here. But you will see them if you stand out a while on a calm night.

I was walking across the yard in daylight one day and a little brown bat flew out of the trees, hovered about three feet from me sizing me up for about ten seconds and flew off. I thought it was a neat experience.

No one has determined whether the little brown bats here in interior Alaska hibernate or migrate. I'd like to attract some; I know they've been sighted very close to our land. A friend of mine had some roosting beneath the siding of his house and I saw those, but they're pretty elusive and most people I know here have never seen one.

Not an expert here, but we have a huge bat population in my area. As far as I can tell they like to be near bodies of water. Don't know if you have any water features on your property, but if not that might be an opportunity to make your land more attractive to them.

I do have springs, but no open water, however I'm planning to try a hog-sealed pond at some point. I do know they're around, though, because a lady I know had one get in her house within a mile or two away.

I was thinking about this after my last post. Besides a couple WW2 anti ship installations, there are no real caves around here. I don't think there needs to be big crevasses for them. Maybe a few mini adobe caves would work?

The bat is probably one of the most misunderstood and maligned creatures ever. The bat may never be your pet but the advantages of bats is undeniable.

One of the myths about bats is that they serve no useful purpose and are just disgusting flying rats. Think about this; in Central Texas alone, bats consume about 2 million (2,000,000) pounds of insects an hour during the summer months. The farmers are loving that and some of these farmers are putting up bat houses because of the loss of habitats for bats. These bats save the farmers millions of dollars in damage because of the voracious appetites of these bats.

Recently, I was experiencing severe insect infestations in my area, so I decided to build a bat house for the solution to my problem. As bats are the perfect nocturnal insect killer, they can devour up to a hundred insects like mosquitoes, moths, leafhoppers and other insects which are harmful to crops.

Personally, I've been using a very helpful resource for my bat house building plans. You may check it out here: http://www.merlintuttle.com/bat-house-builders-handbook

I'm new to the site and this is exactly why I joined. I would have never EVER stumbled across something like this. Bats? An artificial bat cave? Amazing!

I LOVE bats! They're amazing animals, and so useful for their insect control. You definitely don't need caves to have bats--any kind of natural or man-made crevice will do. We have bats living under the eaves of our house. They are most welcome, and I love watching them fly out at dusk!

Of course, bats usually carry rabies in North America and should never be handled without proper protection. But enjoy them! They're great.

For the last couple of years we've had what I think is a Townsend bat in a high window behind green shade cloth.  Surprised me!!  It's a window that faces west.   The sun was so annoying we hammered up different colors of shade cloth trying to decide whether to put an awning over it, or take the window out.  Then one day I saw what looked like frog walking across the window under the green shade cloth.  Turned out to be a bat!  It was amazing to watch.  It extended a bat wing and stretched during the day.  It cleaned itself.  It turned its head on occasion.  It waited until it was very dark before it left the window.

Then in early fall a smaller bat showed up, and the bigger bat with big ears was gone.   The smaller bat was in the window regularly all winter, except when it rained.  Then in March the big bat came back!  And started hanging out with the little bat!  The little bat moves away from the big bat, but doesn't leave.  Maybe the big bat migrated south, and when it returned in March it found its special place was occupied.  When the sun hits the west-facing window they both retreat to places where the green shade cloth is doubled over and gives them more shade.   In the past the big-eared bat has struggled on hot days to stay in the window, and sometimes leaves on a hot afternoon.  There are hawks around that are probably a threat to a bat, but they seem to be surviving.

So we installed another small window in the highest part of a shed at about 15 feet, and hammered a double piece green shade cloth over it, and a bat hangs out there during the day.

These are all solo bats, and they drop mice-sized droppings that could possibly have histoplasmosis in them.  So we stay away from the droppings.  I've cleaned off the window sills and hammered on some 45 degree roof flashing above the lower window sill that will cause the droppings to fall out or be washed out by rain.

So amazing to watch these guys!

Austin bats

I watched that TX bat colony grow for 30+ years. I see bats in TN every night during warm weather. They are amazing animals. Put up a few bat houses this summer. Unoccupied so far but they say the bats usually move in during spring. Anything that eats mosquitoes is good. Trying to encourage that behavior.

Being in the frozen wasteland that is north of the 54 parallel in B.C. Canada, I find this a surprising
statement about bat houses:

"They do not provide overwintering protection (hibernation)"

Bat houses. no matter how they are decorated. are still only 3-sided boxes with just enough space at
the bottom opening for them climb in and cling close together for warmth

Somehow the local bat population somehow survives the close to 40 degrees below 0 winters up
here....as do bears. frogs. toads.salamanders...bees...

By the way.just to clarify. 40 below Canadian (celcius) is the same temperature as 40 below in
American (fahrenheit) degrees.....

I am surprised that no one has already mentioned this! A mature shag bark hickory is a favorite spot for some of the bats around here to hang out during the day. I don't think they hibernate there, but they crawl up under the big slabs of bark for much of the year. I do like the bat cave idea, but how would I keep my bat mobile clean with all the guano dropping on it?

Michael Holtman wrote:....... I do like the bat cave idea, but how would I keep my bat mobile clean with all the guano dropping on it?

Michael.....not to worry.  The description of the Batmobile in the Wikipedia entry pasted below indicates that the vehicle came with "shield platings".  I'm pretty sure the the materials in such platings were designed from the beginning to effortlessly shed bat....and other....guano, leaving the roadster eternally exhibiting that "new car shine".

:-)

Anyone dug an artificial bat cave finally, and want to share a picture?

The Monkton bat cave seems interesting and feasible with concrete pipes, a picture of a drawing can be found at the bottom of this link
https://explorekent.org/activities/monkton-nature-reserve/

Thanks for including this thread in the daily-ish mail!
Like so many other wildlife, bats are endangered here in Germany, some species more than others.

Luckily I still see some around our garden at night (but don't know the exact species). In most years, the males join together behind our (fake) window shutters to hang around during the day. I find their droppings on the windowsill below, but it is not really enough to start bothering collecting it.
I know that in some churches in Germany they have bat asylums where they collect their guano and sell it. Churches can claim federal (?) funds for making the necessary structural changes to the belltowers and roofs to allow bats to overwinter and breed. There are special roofing shingles with which you can replace the normal shingles and that serve as entry/exit for the bats.
For those of you with bigger acreage and barns, try to keep some openings for bats and leave old trees with hollows.

Last year we received a bat box from a friend who did not have room to install it. I hope to hang it under the eave of our roof in the next weeks.

And the enviromental group where I am member redesigned an old transformation tower to a bat tower:
Bat tower

Apart from that, I try to encourage plants that bloom in the night to attract lots of night-active moths etc. Without insects there will be no bats.

I loved sitting in my carport at dusk waiting for my bats to drop out of their little space between the trailer and the carport. They were well protected year round. They would fly in a circle around my head inside the carport and then head out into the woods. I didn't have a garden back then but never saw a mosquito. There was never a fear that they would crash into me since their radar was so good. I hope I can create a similar environment here.

I fix roofs. Come across them often. This one did not leave for ages. Just sat there.
I’ve noticed an uptick of them since i converted ghe garden from lawn to biodiversity garden. Very few mosquito bites since. We used to need a net when we moved in.

We have always had bats, but when they took out the orchard on the north and west side of us they seemed to disappear. Along with a lot of other critters. We also seemed to get every squirrel, rat and mouse in the area.  Thank goodness they planted a new orchard two, maybe three years ago.  Things are starting to balance out this year.  We seem to have bats living in our front pomegranate tree.  I'm all for getting as much help with keeping the insect population under control as I can get.  I would like to help the bat population as well.  I'm going to have to build a bat house.

I saw this thread mentioned in the daily-ish. I thought of how lucky I am to live in a neighborhood with bats! When I walk the dog in the evening (it's starting to get dark) I see them flying around between the linden trees (also called lime trees). I don't know if they live in the trees (sleep there during the day), or maybe in the fairly old buildings at the other side (small industrial buildings from the 1950s or '60s).
Probably they are Pipistrellus pipistrellus. That's the most common bat species where I live.

My guess, the Linden trees have fruit (limes?) that attract bugs the bats like to eat. But they roost in the buildings siding or attic space.

Lorinne Anderson wrote:My guess, the Linden trees have fruit (limes?) that attract bugs the bats like to eat. But they roost in the buildings siding or attic space.

Hi Lorinne. Although some call them Lime trees, they are not the trees producing limes. Limes are a tropical citrus fruit. Linden trees are cold / temperate climate trees. They flower (the flowers are known to have a lot of nectar, attracting many bees), but the 'fruits' are only tiny hard balls ... The bats here eat insects, but I don't think they eat the bees. I think they eat the small mosquitos (gnats, or whatever you call them).

We have lots of bats on our property. We love them. There is a natural bat cave down by the creek that I live by. It's really cool. I'll try to get a picture.