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Bats - your most effective insect control

 
Amedean Messan
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I am looking into designing habitat for bats in an agricultural setting while looking into research on cost savings that these interesting creatures may provide to a farmer. 



For example, lets look at the Little Brown Bat (Myotis lucifugus)





  • Life expectancy is between 1 to 30 years
  • Eats typically 1,200 insects in just one hour (grossly more effective then insect carnivores)
  • Typically consume 50 to over 100 percent of their body weight per night (weigh on average .42 ounce)
  • Consumes moths, gnats, crickets, locusts, mosquitoes, fruit flies, and other crop pests but not exclusively.
  • Compatible pest control measure with bees (bats are nocturnal)


  • SO what are the options that I have to more bats? Most people make or buy bat houses but here is my problem with them.

  • Require maintenance
  • You will need many (to say the least) for high capacity populations
  • They do not provide overwintering protection (hibernation)
  • Eventually need to be replaced
  • Wasps have a tendency to nest



  • As far as my research has led me, I believe a man made bat cave is an ideal solution.  Because their fixed durable structures, bats are much more likely inclined to populate these for long periods of time.  These provide space for hibernation, breeding, and are preferred habitats to bats.  Bats are social animals that enjoy the safety gained in large populations, which is why you often see them in communities.  Eventually as the artificial cave develops a  profile with the bat community, it will bolster local population levels of benefiting bats which will in turn benefit farmers.

    An example of a bat cave.



    The largest bat cave in the world is located in Texas at Bracken cave.  It houses an estimated 20 million bats in a roughly 5 acre complex. If I use this to scale the size requirements of an ideal man made bat cave then a cave with an area of 1/8th an acre should be able to house half a million bats.  Also ceiling height is an important consideration but I am lacking on sufficient data to make any educated calculations.  Now if I use this ideal population goal I can calculate the predatory impact on the local environment.

    500000 (population)x .42 (weight of each bat in ounces) x .75 (ratio of body weight eaten) = 157500 ounces of insects eaten

    Exactly 9843.75 pounds of insects eaten per night from a population of half a million bats residing in an 1/8th acre cave at full occupancy.

    Even with a decent margin of error  and a quarter of the capacity the local impact on insect populations is amazing.  I am honestly surprised that I do not see this type of data on bats in these forums.  In my opinion, bats provide the best high volume insect control solution uncontended.  But lets be honest, the population figure here is extraordinary.  I merely wanted to state the potential of the scheme.  Lets look at a more realistic calculation.  Lets assume I built the cave and after a few years the population grew to a modest 6000.  This number seems large, but also consider that building a bat cave is not a thing to measure instant results and that it takes time to develop a mature system.  It is incredibly difficult to mathematically calculate the growth rate of a bat population.  There are many design considerations including the location and design of the entrance to increase profile.  In many respects it can be considered a creative skill versus a function of growth.  So moving on to my calculation,  with this number we can predict the following.

    6000 (population)x .42 (weight of each bat in ounces) x .75 (ratio of body weight eaten) = 1890 ounces of insects eaten

    Exactly 118.125 pounds of insects eaten per night from a population of 6 thousand bats in a modest setting.

    A fraction of those insects can produce a lot of damage to a farmer.  In 118 pounds you are looking at millions of insects.  Not even liberal application of pesticides can produce results as good without costs or concerns on the environmental health hazards.  Other then an investment on the construction, money and some time a bat cave is a self sustaining measure to control insects in your permaculture designs.  For examples of man made habitat I found a good read on a bridge that supports a colony of 600 thousand bats at http://www.batcon.org/pdfs/BATSmag/BATSSummer05a.pdf


    Common myths:

    Bats are unfairly stereotyped as rabid.  There is a myth floating around that 1-5% of bats have rabies.  This is a misinterpretation from a statistic on bats being sent to the lab for testing.  From the suspected infected bats sent to the lab only 5% actually test positive for rabies.  Because of lack of understanding what this means, the inaccurate statistic was made and carried on to bat populations in general.  In actuality, bat attacks are incredibly rare.  Most of these attacks were completely avoidable by people who put themselves in these situations.

    So here are some good links for researching.

    http://www.bathouseforum.org/forum/   (community of enthusiasts like here)

    http://www.batcon.org/   (organization for bat research and conservation)
    http://www.life.umd.edu/faculty/wilkinson/honr278c/PDF/Miller01.pdf (data that supports concepts for insect electronic warfare)


    Texas - Selah Bamberger Ranch Preserve

    Completed in 1998, the Chiroptorium is designed to house 1 million Mexican Free-tailed Bats. For the first few years, bats came and went. Most seemed to be travelers; they would stay for a few days or sometimes for a few months. There was much early publicity, as everyone was anxious to report about this eccentric project and predict what the results might be.

    http://bambergerranch.org/the-bats-of-selah/






    Tennessee - Cave & Karst Program for the Conservancy in Tennessee

    The concrete box buried in a hillside is almost as long as a basketball court, but only half as wide. It has surveillance cameras that detect heat without getting warm or making any noise due to the possibility that any noise disturbance could be a deter the bats moving in. The goal is to offer bats a safe winter home, where every summer humans could go inside and clean out any lurking fungus, keeping white-nose syndrome in check.

    http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/tennessee/artificial-bat-cave-2012-large.pdf (detailed plans for the artificial cave)





    For more information on the project:
    http://www.batcon.org/index.php/media-and-info/bats-archives.html?task=viewArticle&magArticleID=585
    http://www.bambergerranch.org/facilities/bats.phtml    

    [Edited to fix formatting as requested by the author in this thread http://www.permies.com/t/27072/tnk/Refurbishing-thread]

     
    Leila Rich
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    I want bats!
    Our two endemic species (the only native mammals!) are practically extinct on the mainland.
    Thanks people, with your axes, DDT, cows, cats, possums, stoats etc, etc...
    Having a bat at my place would be like you having...what's really small, really rare and really elusive in your neck of the woods?
     
    Alex Slater
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    Leila, what's the distribution of our native bats these days? I'm heading back to NZ this year and will be getting some land around the BoP. It would be nice to set up some bat habitat.

    But it's been a while since I've been in NZ and even then bats were pretty much endangered!
     
    Susanna de Villareal-Quintela
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    We have a colony of brown bats in our log cabin.  They love living in the rafters of these old logs.  We have to move them out of the house because the guano can contaminate the indoor air.  I have no idea how big our colony is but we don't want them to be killed.  We're trying to work with conservations groups to better understand where to build a new shelter but, sadly, the conservation groups do not seem to be very responsive. 

    They are fun to watch, like swallows following the the horses through the grass.  Very curious creatures and efficient. 
     
    Tyler Ludens
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    This month's Bats magazine from Bat Conservation International has an article about using bats to control insects in Texas pecan orchards. 

    Everyone should join Bat Conservation International, in my opinion. 

    http://www.batcon.org/
     
    John Polk
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    Two factors often overlooked when building bat houses/habitat:


  • Water.  Like all animals, bats need water to survive.  Water also attracts insects, which they eat.

    Echo.  Bats use echo navigation (like a submarine's sonar).  Flat surfaces and square corners help create a good 'homing device'.  If you modify (or even repaint) after colonization, you may be altering the echo pattern.
  •  
    Amedean Messan
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    Thank you, yes, I completely forgot to add information in regards to water.  I did not get into the specifics of bat cave design but it is essential for the bats to have an adequate supply of water.
     
    Dave Miller
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    Bats are in big trouble due to White Nose Syndrome.  Little Brown Bats may be going from our most common bat to endangered or even extinct in just a few years.

    http://www.cbsnews.com/stories/2011/07/12/earlyshow/living/petplanet/main20078755.shtml?tag=mncol%3Blst%3B2

    I have built several bat houses which are occupied.  People have made artificial bat caves before, I'll see if I can find the link.

    The friendly folks over at www.bathouseforum.org are the real experts on bat houses.  Tons of expertise there.
     
    Jonathan Byron
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    "Robin, to the bat cave!"

     
    Milton Dixon
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    I taught at a summer camp for many years. One of the things that I enjoyed the most was watching the bats fly out of the old boiler chimney at sunset. Lots and lots of 'em.
     
    Leila Rich
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    Excuse me people, while I go off on a tangent and slip into acronyms, New Zealand's unofficial native language...
    ajsl, DOC  bat distribution maps don't show populations in the BoP at all, so it's back to
    Leila Rich wrote:
    axes, DDT, cows, cats, possums, stoats etc, etc...



     
    Dave Bennett
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    I hate 4 bat houses out back on the trees.  They are the little homemade versions.  I had 5 of them but one disappeared.  They are all occupied but the first year they sat empty.  The mosquito population went down substantially during the third summer.  I am not sure how many are living here because when you look up inside in the daytime there is just a single blob of brown fur.  But all of the houses are full.  They have been living here for about 14 years now.  I love the little critters.
     
    Dan Poole
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    Does anyone know any rules of thumb for designing a bat cave? A few design considerations come to mind:

    - Internal area, volume, ceiling surface area
    - Opening size
    - Opening aspect ratio
    - cave depth
    - light penetration
    - temperature
    - humidity
    - water nearby
    - wall material

    How do you attract them or do they even need attracting if the cave is appropriate?

     
    Dave Miller
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    Dave Miller
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    You can also build a giant bat house:

     
    Dave Miller
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    Or a not so giant one:
     
    Milton Dixon
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    Instead of making all your calculations, why don't you go to a junk yard and find something that might work but could also be re-purposed if it doesn't. Or make one of Sepp's cellars but leave the door unfinished and see if the bats like it?
     
    Dan Poole
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    Thanks for the links Adunca! The University of FL bathouse sure looks easier to build than the bamberger ranch house (rebar and shotcrete domes). This link shows various types of bathouses and has a bottom view of the UoF bathouse. It pretty much looks like the smaller houses in the last video.

    http://www.floridabats.org/BatHouses.htm


    miltonics - Knowing what bats like can at least guide your decision, but yes, if there is something that could be repurposed, why not use that?
     
    Jordan Lowery
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    adunca that first video is amazing. i want to build one of those now.
     
    Dave Miller
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    hubert cumberdale wrote:
    adunca that first video is amazing. i want to build one of those now.

    Yes just think, each one of those bats is going to eat up to 1,000 insects per hour throughout the night.  We're talking mind-boggling bug consumption.

    Contrast this with one of those electric bug-zappers.  I read a study once that clocked those at killing a whopping 50 insects per hour.  And those kill both "undesirable" and "desirable" insects.  Bats tend to prefer the insects that we find "undesirable" - moths, beetles, flies, and, if nothing else is available, mosquitoes.
     
    Dave Bennett
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    Dan Poole wrote:
    Does anyone know any rules of thumb for designing a bat cave? A few design considerations come to mind:

    - Internal area, volume, ceiling surface area
    - Opening size
    - Opening aspect ratio
    - cave depth
    - light penetration
    - temperature
    - humidity
    - water nearby
    - wall material

    How do you attract them or do they even need attracting if the cave is appropriate?



    There are lots of free plans available on the net.  Just like in Field of Dreams.......
    "If you build it....they will come."
     
    John Polk
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    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!
     
    Dave Miller
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    John Polk 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!


    Yes, it is worth $10 a pound: http://www.amazon.com/Earth-2-Pound-Guano-10-6-2-7843/dp/B004OVYIV8
     
    Jordan Lowery
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    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.
     
    Dave Bennett
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    My bat houses are small but the guano piles up pretty quickly albeit small piles but some bat poop is better than none. 
     
    Ken Peavey
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    The UF-Gainesville bathouses are about an hour and a half drive south of me.  20 miles to my west is The Spirit of the Suwannee Music Park where they claim to have the largest bathouse in the world.  I've seen that one, and while there are 10s of thousands of bats, I can't verify their claim.  Under the bathouse is a big pile of guano which the park spreads around flower beds, fields, and grassy areas.

    I spoke with a guy who worked at the park about the bats, and how to draw them in.  Mind, you, he was no expert, just a guy who worked around the park, but seemed to have some idea what he was talking about.  As long as you offer food, water, shelter, the bats will move in.  Shelter is easy-thats the bathouse.  A water source is as easy as a tub, pool, river, pond-and don't worry about standing water growing mosquito larvae.  Drawing in the feed can be done with a bug zapper.  Plug it in, the bugs will swarm.  It may take a while, but sooner or later the bats will find the food, the water, and begin occupying the shelter.

    --
    10 bucks a pound??!!  I'll need to give this a closer look!

    --
    An important feature here is that the bats harvest nutrients from the surrounding area, not only from around the farm.  I can gather compostable material from under the trees, but I'm just moving the nutrients from one spot to another.  There is no net gain of nutrients on the property.  If I could offer shelter for several thousand bats, and the critters produced a wheelbarrel load of guano in a day, every day, then I would have a perpetual source of outside nutrients without putting in perpetual effort. 

    If these critters can produce 100 pounds per day and I can get half of that $10/# retail price, thats a little better than what I earn now, and I dont have to put on a hazmat suit.  All the tools needed for this operation are described or linked somewhere on these forums:
    -bathouse plans right here
    -solar dryer
    -look in the worm thread for vermicompost sifter
    It's enough to develop a uniform product ready for market.  I'd want to package it in a reusable bucket.

     
    Amedean Messan
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    The problem with bat houses are that they do not provide the protection they need during the winter when there is little food and give little roosting support.  What I am proposing is a more permanent structure.  Permanent structures will encourage much larger populations to make permanent residence and it can even potentially become a profitable enterprise in the guano market.
     
    Ken Peavey
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    What about those Sepp Holzer style underground livestock shelters?  Make the thing longer.  Close up part of the front, it would be more cave-like.  Imitate nature. 
     
    Dave Bennett
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    Amedean wrote:
    The problem with bat houses are that they do not provide the protection they need during the winter when there is little food and give little roosting support.  What I am proposing is a more permanent structure.  Permanent structures will encourage much larger populations to make permanent residence and it can even potentially become a profitable enterprise in the guano market.  I will update my post with bat cave design considerations from my research tonight.

    I live in a mobile home park and have for almost 18 years.  My bat houses have survived with very little maintenance. One did disappear though.  I think someone took it because the mounting screws are still there.  All 4 of them are very well populated and they have been that way for 14 years.  Winter here is short compared to some places but it does get cold here.  I always put up bat houses where ever I live.  I have been helping bats have a place to call home for about 30 years.  Sometimes ya just gotta do what ya gotta do.
     
    Amedean Messan
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    I would only recommend  sepp holzer style underground livestock shelters if they do not have any biodegradable materials least the ceiling cave in.  I would hate to develop a colony of bats in the thousands only for the thing to cave in after a decade.
     
    Ken Peavey
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    I've seen log cabins which have held up for 100+ years.  The Holzer shelters are protected from weather/wind/water and I can see them holding up for decades at least.  The ceiling from the inside would be grabbed by the bats, but would not be in contact with guano which would accelerate decay.  The walls, however, could benefit with a protective surface.  Mud/stucco/adobe would do the job.  Being inside, any available construction materials should offer ample protection for the walls.  Making the walls double thick with logs offers a simple solution.

    If the shelter were to fail, there would be plenty of warning.  It takes years for logs to decay.  As they decay, they weaken.  This should be visible as the roof would sag.  Walls weakening would also present as a sagging roof, but on the sides rather than in the middle.  Even then, not all the logs would fail at the same time.  Should a log fail the shelter would still retain its function.  The housing capacity might be reduced, but I suspect this sort of bathouse would last for decades before transforming into a hugelkulture mound.
     
    Amedean Messan
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    Log cabins have lasted 100+ years, but they still degrade.  Essentially it is up to you but bats can inhabit caves beyond those years.
     
    Dave Miller
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    Before attempting to build a suitable winter roost I would do a LOT of research on winter roost requirements of your local bats. 

    If you live somewhere that does not have night-flying insects in the winter, your bats will go into torpor or hibernation in the winter.  If you do have night-flying insects in the winter, they probably do not go into torpor or hibernation (or only during cold weather).

    Bats have very, very specific requirements for hibernation sites:
    1. Stable, cool temperature above freezing.
    2. Stable, high humidity.

    This is why they prefer caves for hibernation/torpor.  If the temperature gets too cold, they freeze to death.  If it gets too warm, they rouse from hibernation, burn up their fat reserves, and starve to death.  If it gets too dry, they lose moisture through their skin and die from dehydration.  Some species wake from hibernation occasionally and drink the condensed moisture off their fur - without which they would die of dehydration.  Different species have different temperature and humidity needs.

    Note that the man-made cave in the video is not used by bats in the winter.  The bats using that cave are Mexican free-tails, which migrate to Mexico for the winter.  However most other North American bat species hibernate in caves and mines in the winter.

    So any man-made structure which would be used by bats in the winter would have to very closely mimic the temperature, air flow, and humidity of caves that the bats in that area are used to.  I would guess that it is the stable humidity that would be hardest to mimic.

     
    Ken Peavey
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    Doing a little homework...
    Looking at How bats roost over at How Stuff Works

    I'm looking for ideas on enhancing a bathouse, comparing designs.  I'm looking for information on roost design.  All I've found so far is suggestions to kerf the boards used in constructing a roof in order to offer more roosting points.

    Amedean is looking for long lasting design.

    I've got a bunch of wire fence that needs to be replaced.

    Putting all this together...
    What if I used that wire fence on the ceiling of a bathouse?  Its galvanized and still has lots of life left to it, just its all bent up.  If the bats were in less contact with the structure, it would reason that the structure would last longer due to less traffic wear.  The bats get a perch that fits their feet easily and strong enough to support their weight.  For added strength, fixing the fence to the ceiling every foot or so will hold up a (collective noun for bats) of bats.
     
                                              
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    This information is fascinating!!!
     
    Dave Bennett
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    Where I grew up in upstate NY bats don't live in caves.  There aren't any caves.  I imagine that if there were caves that they would choose them as home though.  It gets down to zero and below here in Va. most winters and even colder for much longer periods in NY.  The bats that live in the small houses I built for them here 17 years ago are filled to capacity.  In the daytime if you look up inside them you see a brown blob of fur in all 4 of their little "condos" that are attached to trees at the back of my lot.  In NY when I was younger lots of colonies of bats often over wintered in the steel superstructure beneath the bridges over the river.  They did not freeze to death and it is pretty much out in the open 40 feet or so above the river.  I have seen clusters of them during the summer months in trees along the river in areas where there are no man made structures.  I have no clue where they hibernate when they are living out in the woods but there aren't any caves in that region.
     
    John Polk
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    Years ago, I visited an abandoned fort in the "British West Indies", and while wandering through the underground 'arsenal' where the kegs of black powder used to be stored, we ran across a small colony of bats.  There were sections where the guano was piled several feet thick.  It was in an environment where the temperature/humidity did not fluctuate more than a few degrees from summer/winter, nor day/night: ideal conditions for the local bats.  There might have been a couple of hundred pounds of guano there (after 150 years since the Brits got booted out of there).  Do not expect to retire off of bat guano sales...just be thankful for some free premium fertz recycled by your friends that ate those nasty things that wanted to bite you.
     
    Dave Bennett
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    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.
     
    Dan Poole
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    I wonder if bats would live in the eaves of a house. You could fill that space with boards separated by whatever gap size they seem to like. Then you've got nice stinky guano falling all around your living space....hmm not so good.

    What about putting individual bat houses on crop trees or on poles in the middle of your plantings? Then you have passive guano collection by your plants.
     
    Dave Miller
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    Location: Zone 8b: SW Washington
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    Dave Bennett wrote:
    Where I grew up in upstate NY bats don't live in caves.  There aren't any caves.  I imagine that if there were caves that they would choose them as home though.  It gets down to zero and below here in Va. most winters and even colder for much longer periods in NY.  The bats that live in the small houses I built for them here 17 years ago are filled to capacity.  In the daytime if you look up inside them you see a brown blob of fur in all 4 of their little "condos" that are attached to trees at the back of my lot.  In NY when I was younger lots of colonies of bats often over wintered in the steel superstructure beneath the bridges over the river.  They did not freeze to death and it is pretty much out in the open 40 feet or so above the river.  I have seen clusters of them during the summer months in trees along the river in areas where there are no man made structures.  I have no clue where they hibernate when they are living out in the woods but there aren't any caves in that region.

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

    What is white-nose syndrome?

    In February 2006 some 40 miles west of Albany, N.Y., a caver photographed hibernating bats with an unusual white substance on their muzzles. He noticed several dead bats. The following winter, bats behaving erratically, bats with white noses, and a few hundred dead bats in several caves came to the attention of New York Department of Environmental Conservation biologists, who documented white-nose syndrome in January 2007. More than a million hibernating bats have died since. Biologists with state and federal agencies and organizations across the country are still trying to find the answer to this deadly mystery.

    We have found sick, dying and dead bats in unprecedented numbers in and around caves and mines from New Hampshire to Tennessee. In some hibernacula, 90 to 100 percent of the bats are dying.

    While they are in the hibernacula, affected bats often have white fungus on their muzzles and other parts of their bodies. They may have low body fat. These bats often move to cold parts of the hibernacula, fly during the day and during cold winter weather when the insects they feed upon are not available, and exhibit other uncharacteristic behavior.

    Despite the continuing search to find the source of this condition by numerous laboratories and state and federal biologists, the cause of the bat deaths remains unknown. A newly discovered cold-loving fungus, Geomyces destructans, invades the skin of bats. Scientists are exploring how the fungus acts and searching for a way to stop it.

    -- http://www.fws.gov/whitenosesyndrome/


    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
     
    Have you seen Paul's rant on CFLs?
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