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World’s First Artificial Bat Cave Provides Model for Future By Merlin Tuttle\n\nModern bats face a serious housing shortage. Millions of homeless bats have died when their caves were destroyed or converted to exclusive human use, not to mention when old-growth forests were logged.

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World’s First Artificial Bat Cave | Merlin Tuttle


By Paula:

August 14, 2016

World’s First Artificial Bat Cave Provides Model for Future

By Merlin Tuttle



Modern bats face a serious housing shortage. Millions of homeless bats have died when their caves were

destroyed or converted to exclusive human use, not to mention when old-growth forests were logged. Often,

the single most important action we can take to restore bats today is to provide alternative homes.

We know from long experience that desperate bats often

readily occupy human-made structures, from abandoned

mines and railroad tunnels to old buildings. Though building

backyard bat houses is an excellent way to help, sometimes it

is very much in our mutual interest to provide long-lasting

structures that can accommodate large numbers, not only for

pest control, but also for the pure entertainment large

colonies can provide.

When J. David Bamberger was first introduced to an evening

emergence of the millions of Brazilian free-tailed bats

(Tadarida brasiliensis) at Bracken Cave in the Texas Hill

Country, he was awestruck. He fell in love with this wonder of

nature and soon began asking if it would be possible to attract

a miniature Bracken colony to his ranch. Undaunted by an

absence of caves, he asked me about the feasibility of

“building” a cave. Would bats come?

Knowing that such a project could prove costly, I was

reluctant to promise success but noted that numerous

abandoned mines and tunnels had attracted large bat populations. It seemed nearly certain that a cave made-

to-order to meet free-tailed bat needs should be a big success.

As the founder of Church’s Fried Chicken, Mr. Bamberger had

the needed resources and a 5,500-acre ranch. Feeling

reasonably confident of my understanding of bat needs, I

offered to help. He recruited an industrial design engineer, Jim

Smith, who quickly became fascinated, and began to convert

my knowledge of bat needs into structural reality, a bit more

than any of us anticipated! Twenty tons of rebar and 300 cubic

yards of gunite (12 inches thick), a type of concrete used in

making swimming pools. And it all had to be located in a

ravine where it could be covered over with earth and

vegetation, while allowing for natural drainage.

I advised that these fast-flying bats would want a large

entrance and spacious interior with domed ceilings and lots of

roughened, but not sharp-edged surfaces to provide safe

footing for their pups. We provided a curving entry passage

approximately 15 feet tall by 12 wide and 30 long, leading to a

main roosting chamber 43 feet in diameter and 20 feet tall

with a domed ceiling. Then a slightly smaller passage led to a

smaller second room intended for cave myotis (Myotis velifer)

who do not require such large dimensions. Initial

experimentation proved costly, but Bamberger’s estimated

cost to replicate the final design was $50,000 (in 2003 dollars).

The entry passage needed to curve just enough to block direct

sunlight, which could increase risk from hawks and other bat

predators. In case of overheating, we even included adjustable

vents. We also hung several about two-foot-wide, wooden bat

houses with 3/4-1-inch wide roosting crevices in the main

room, in case the first arrivals might be extra choosy about

their security. My reasoning was that once a core colony

accepted the site, that others would be attracted to join them,

gradually spreading out across all or most of the roughened gunite surfaces.

The new “chiroptorium,” as Bamberger called it, took

approximately seven months to design and build, due to lots of

early experimentation. It was completed and covered in earth,

with vegetation planted by August 1998. Prior to being covered

the inside temperature sometimes rose as high as 121 degrees

F, but once protected by soil, it dropped to 88 degrees, ideal

for mother free-tailed bats. By mid-October 15 cave myotis

and a single free-tailed bat had arrived. Several hundred

arrived the following year, several thousand the next.

Suddenly, one summer evening in 2003, Bamberger looked up to see a great column of free-tailed bats, later

estimated at 200,000, and was amazed to discover they were emerging from his chiroptorium. From then on

the colony quickly grew, and based on area covered and average clustering density, likely approached 500,000

when I personally entered to photograph the colony on July 29, 2016. We originally designed the structure to

shelter up to a million, and several lines of evidence suggest that occupancy sometimes reaches that number,

including a few weeks earlier in 2016 prior to the young learning to fly. Several thousand cave myotis have also

been spotted using the smaller inner room.

Whenever I see construction materials for sale, I can’t help but

wonder which new discoveries might now be available for

enhancing construction at reduced cost. Lots of bats still need

homes, so I’m hopeful that the Bamberger chiroptorium is just

the first in a long line of improved designs. Countless large bat

caves have been lost permanently to limestone quarrying,

highway and housing construction and to commercialization.

However, we’ve repeatedly seen how large populations can

rebuild, and recent discoveries demonstrate likely cost-

effective returns in crop protection, guano harvesting (for

fertilizer) and ecotourism. Mr. Bamberger’s bats migrate south for the winter, making guano harvest practical

without harm to his bats. And he intends to replace use of commercial fertilizer in his pastures with “home-

grown” natural fertilizer in the year ahead.

J. David Bamberger’s chiroptorium is a perfect fit for his long-

term goals. He purchased the worst piece of over-grazed ranch

land he could find in 1969 and named it the Selah, Bamberger

Ranch Preserve. Located in Blanco County, deep in the Texas

Hill Country, the land was overgrown in Ashe juniper and

lacked running water. Bamberger’s goal of using his wealth to

demonstrate how even the most damaged land could be

restored, has been a monumental and award-winning success.

Today, having replaced countless acres of water guzzling

juniper with native grasses, he has year-round flowing springs

and a dramatic return of wildlife, including two species of endangered songbirds.

His workshops and nature tours for children, fellow ranchers and the scientific community are based on well-

established fact, not on computer models. He’s truly passionate about inspiring visitors for a better future, and

the chiroptorium is now his centerpiece and favorite attraction.

I’m hopeful that Bamberger’s bold first step will make a wonderful difference for bats and the humans who

benefit from their services worldwide. We’ve still much to learn and even more to demonstrate. For more

information about the Selah, Bamberger Ranch Preserve and Chiroptorium. If you’re serious about building

expansive homes for bats, keep in mind that their needs vary according to species and geographic region. J.

David and I share a passion for expanding his early success, and we’re both happy to provide guidance.

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