Bat Houses

Bat House Warnings – A Reality Check

Bat Houses

5/6/21
Merlin Tuttle

Observations of heat-stressed, sometimes dead bats associated with bat houses, have led to unfortunate speculation that bat houses can become ecological traps that lure bats to their death. It is true that numerous bat houses are badly built and sold with unreasonable claims and little, if any, instruction on bat needs. Vendors of such houses defraud customers and threaten the credibility of bat conservation. Both vendors and customers can benefit from education and certification. Nevertheless, there is no evidence that poorly constructed bat houses threaten bat survival. Bats are smart enough to avoid bad bat houses except when desperate from lack of alternatives.

Loss of vast numbers of traditional roosts is a key cause of bat decline. Most species that occupy bat houses today originally relied on loose bark and cavities in snags that were often lost during storms. This likely explains why bats prefer to live where multiple roosting options are available.

Radio tracking studies show that occupants of natural roosts frequently move among several, apparently to escape predators and parasites or find optimal temperatures. During severe weather, large numbers may die even in traditional roosts. With so few remaining, bats often fail to find ideal homes.

When providing bat houses, the best way to reduce mortality is to offer a variety of roosting options. Several houses ideally should be colored, positioned, or vented to provide a range of temperature. Needs vary between cool versus hot weather extremes.

Selecting a quality bat house, as well as proper placement, are crucial to success. In our forthcoming book, Danielle Cordani and I will provide plans for houses that maximally meet bat needs over a wide range of temperature. However, a single house is unlikely to prove ideal for all species and locations.

Northern long-eared myotis (Myotis septentrionalis) emerging from beneath tree bark. Many bats roost beneath lose bark on old snags.
A nursery colony of Fringed myotis (Myotis thysanodes) reared young beneath exfoliating bark on this old snag in Arizona.

Where sufficient habitat exists, especially within easy reach of overwintering locations, available houses often become crowded, and growing numbers of young may perish for lack of available space. The same occurs at traditional roosts. We simply don’t see it. And we can’t prevent it, though careful monitoring and providing more bat house options can help.

Selecting a Quality Bat House
Finding, Protecting, Restoring America's Historic Bat Caves

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Improving Bat Houses in America:

Bat Houses

Nearly 40 Years of Progress and Still Learning

9/14/2020

By Merlin Tuttle

Bat houses are outstanding tools for education. When I introduced them to Americans in 1982, my primary objective was to help people overcome fear and accept bats as valuable neighbors. That goal has been vastly exceeded. Today, hundreds of thousands of American bats live in a wide variety of bat houses.

Individuals who have carefully tested local bat preferences, and adapted accordingly, are reporting close to 90 percent occupancy. Nevertheless, there is still much to be learned. And that is why we’re initiating new collaborations.

Late last month, local member, Debbie Zent, founder of Austin Batworks, reported an impressive event. Her three-chamber nursery house had been caulked, sealed, and painted inside and out, and was mounted high on a streamside ranch building—a nearly perfect combination. But to find it overflowing with occupants just days later was surprising.

This Texas Hill Country bat house became overcrowded within days by Brazilian free-tailed bats (Tadarida brasiliensis).
The house was ideally located approximately 18 feet up on a building beside a permanent creek where it receives only morning to mid-day sun.

Was this extraordinary success due to house or location quality, or were these bats simply desperate?

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A School Where Bats Are Welcome

Bat Houses, Conservation

7/11/19
By Merlin Tuttle

 

Ariel Miller documenting installation of her school’s new bat houses.

Skybridge Academy is doing something new! While many school administrators might panic at the sight of a bat in the yard, Ariel Miller, founder of the school in Dripping Springs, Texas, recently invited us to install two bat houses in her schoolyard. She hopes to attract hundreds of Brazilian free-tailed bats (Tadarida brasiliensis) and use them as teaching aids across Skybridge’s custom-made curriculum.

 

To put it mildly, the school is innovative! The yard includes a pair of pigs, a beehive, a vegetable garden, and now deluxe housing for bats. Students choose their own subjects and learn practical skills, completely omitting standardized testing. Skybridge alumni have an outstanding track record of achievement regardless of whether they opt to pursue higher education or another career path. (more…)

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Young Conservationist Makes a Difference

Bat Houses, Conservation

Young Conservationist Makes a Difference
12/6/18

Anyll Markevich is a young man with a mission. He writes to Merlin, “I became interested in bats thanks to your book, The Secret Lives of Bats. It is one of my favorite books, and I have recommended it to more people than I can count! I have always known bats were cool, but not to the extent I discovered in your book. I want to be a wildlife biologist or ethologist when I grow up, so your book easily fascinated me.”

 

Anyll is far more than just interested. He’s also busily helping bats. He has written letters to editors in response to our Bat Flashes but wanted to do more. Using photos from our photo gallery, he designed his own bat brochures which he handed out to people at a local pedestrian mall. However, people were preoccupied with shopping and didn’t seem too interested.

 

He then emailed Merlin for advice on how to build bat houses that would best accommodate bat needs in the mountain climate of Colorado. He built nine, keeping one for himself, and sold seven to raise funds he donated to MTBC to help bats. But, being a very inventive 14-year-old, he passed his $100 gift through his father, who’s company matched his funds dollar for dollar through American Online Giving Foundation.

 

Lacking an ideal location for his bat house, he had to mount it a bit low, late in 2016. By the next summer, he found his first occupant. This year, Anyll and his mom noticed several bats flying around their yard for the first time. He checked his bat house and counted up to five. They’ve now left for winter, but he’s optimistic that he has the beginning of a colony. He’ll soon contact his customers, each of whom received instructions and one of his brochures. He’s hoping to hear of further success.

 

In his most recent communication, Anyll reported, “There is an exciting new development! Our local library (Boulder Public Library) wants me to build a four-chamber nursery bat house.” Furthermore, he got to meet professor Rick Adams, a well-known bat researcher and fellow conservationist from the School of Biological Sciences at the University of Northern Colorado. Rick will be consulting on placement of Anyll’s bat house, making Anyll very proud! His next objective is to convince the librarians to permit him to provide his brochures to interested library users.

 

 

 

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Collaboration to Improve Housing for Bats

Bat Houses

9/20/18

Harrison (standing) and Christopher showing off their new BatBnB houses.

For the past 18 months Merlin has been assisting Harrison Broadhurst and Christopher Rannefors in creating a line of designer bat houses, attractive to both home owners and bats. Their curving architecture isn’t, just pleasing to the eye. At least theoretically, it may increase the area available for roosting, since most bats appear to prefer to line up with faces exposed to the outside air, not to another’s posterior, quite understandable!

The new houses are constructed of kiln-dried, sustainably sourced, three-quarter-inch western red cedar, with each piece dovetailed and caulked, thus minimizing leakage. Roosting chambers are extra tall (20-26 inches) and vented to ensure thermal gradients preferred by bats. All landing and roosting surfaces provide one-eighth-inch-deep cross cuts at half-inch intervals, ensuring maximum footholds for young bats. By avoiding plywood, the possibility of early deterioration and potential off-gassing are finally eliminated. Furthermore, treatment with Thompson’s WaterSeal Semi Transparent Stain & Sealer will additionally protect against warping.  BatBnBs come with complete instructions and are easy to mount.

We’re proud to be a part of Harrison and Chris’ efforts on behalf of bats and a safer environment. They’ve been featured in dozens of leading publications and have even appeared on several television shows. You can learn more about them and obtain your own BatBnB by visiting their online shop. By using the code MERLIN when ordering you will be given a 10% discount, and the company will donate to MTBC an additional 5% of all orders using this code. Feel free to share this discount and BatBnB’s website with friends and let us know about your progress. By purchasing a BatBnB, you can reduce the threat of harmful pesticides in your neighborhood and help MTBC educate the world about these invaluable neighbors.

 

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chiroptorium design

World’s First Artificial Bat Cave

Bat Houses, Conservation

World’s First Artificial Bat Cave Provides Model for Future
By Merlin Tuttle
8/14/2016

 

artificial bat cave design
The chiroptorium covers 3,000 square feet (279 square meters) and offers about 8,000 square feet (743 square meters) of likely roosting surface. A structure of welded-together rebar, coated in heavy plastic, was then sprayed with a foot of gunite to form a permanent shell.

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.

construction crew at artificial bat cave
Construction crew working in entrance passage. Vertical braces were removed once the gunite hardened.

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? (more…)

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Formosan golden bats of Taiwan

Bat Houses, Conservation, Field Work/Photography

Mr. Chang and mascot of the Formosan Golden Bat's Home

Mr. Chang and mascot of the Formosan Golden Bats’ Home

Following 30 hours of travel, we spent our first day recuperating in Taipei, got up early the next morning for a 2.5-hour drive to the Formosan Golden Bat’s Home on the campus of the Sheng-Zheng Elementary School, where we met our host, 43-year-old Heng-Chia Chang. As a teacher, he had noticed beautiful little golden bats (Myotis formosus flavus) roosting in school yard tree foliage. (more…)

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Photographing North America’s Rarest Bat

Bat Houses, Endangered Species, Field Work/Photography
An endangered Florida bonneted bat, America’s rarest bat, once thought to be extinct.

America’s rarest bat, the endangered Florida bonneted bat (Eumops floridanus), was once relatively common. It often lived in tile roofs of Coral Gables and Miami, and its loud, low-frequency echolocation calls made it easy to detect. The species declined sharply in the 1950’s and early 1960’s, and by the late 1970’s extinction was feared. Then in 1978 woodcutters found a male and seven females in a woodpecker cavity. Soon several more were found living in a backyard bat house.

(more…)

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An Organic Farmer’s Experience with Bat Houses

Bat Houses, Organic Pest Control
DSC00080 (1)
View from above prior to roof attachment.  The sealed-in ceiling between the roof and roosting crevices is for enhanced thermal stability.

Nearly 20 years ago, Frank Bibin, a Georgian pecan grower contacted Merlin for advice on attracting bats to help control insect pests in his orchards. He has since gone organic and become an important advocate for building artificial bat roosts.  To learn of his results go to Pebble Hill Grove–About Bats.

Frank’s first small bat houses were put up in 1998. This video, filmed in Frank’s pecan orchard, tells his early story. It took two years to attract the first bats. Thereafter, numbers grew rapidly. Now that local bats are accustomed to using bat houses, new houses are normally occupied within 30-40 days.

DSC00082 (1)
View from entry (bottom), showing 5 newly installed, 3/4″-wide roosting crevices. One of these houses shelters up to 400 bats.

Through years of testing, he has developed many new innovations. His bat houses and mounting accessories are achieving nearly 100 percent occupancy at many locations in the Southeast and are available for purchase at Frank’s website, Pebble Hill Grove–Bat Houses . Parks and nature centers are among his primary customers.  Though there are many suppliers of smaller bat houses, we know of none better than Frank’s when it comes to long-lasting roosts that attract larger numbers of bats. 

How Frank does it… (more…)

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Bat houses help rice farmers in Spain

Bat Flash, Bat Houses, Organic Pest Control

checking a bat houseWe would like to highlight a recent study of exceptional importance to all who care about conserving bats. As one who has long promoted the potential benefits of attracting bats to artificial roosts, Merlin is especially pleased with the publication of a recent multi-year study documenting the successful attraction of thousands of bats to small, inexpensive bat houses, leading to well documented reduction of rice pests below threshold levels that require use of chemical pesticides.

The study titled, Pest control service provided by bats in Mediterranean rice paddies, appeared in the journal Mammalian Biology and is available for free download at researchgate.net.

A bat house opened to permit checking by researchers

Soprano pipistrelle bats (Pipistrellus pygmaeus), a common bat widespread across continental Europe, east to western Asia Minor, the Caucasus and Siberia

 

The researchers report that properly located bat houses were readily occupied by soprano pipistrelle bats (Pipistrellus pygmaeus), and that as numbers increased damage from rice borer moths (Chilo supressalis) fell sufficiently to eliminate further need for chemical pesticides. They additionally note that the cost of putting up bat houses was 6-8 times less than that of relying on chemical treatments. These authors also provide an invaluable summary of current knowledge of bat values to agriculture. There are numerous opportunities to expand on this pioneering research which is urgently needed. We deeply appreciate the help of Adrià López-Baucells and Oriol Massana Valeriano in providing outstanding photographic documentation of this project.

Iberian rice field where research was conducted

 

Here’s contact info for ADRIÀ LÓPEZ BAUCELLS
PhD student on Bat Ecology and Conservation

Smithsonian Tropical Research Institute – Instituto Nacional de Pesquisas da Amazônia
Lisbon University – cE3c
Museu de Ciències Naturals de Granollers

PERSONAL PAGE
PhD Project Site
Portuguese Research Group Site
Natural Science Museum of Granollers

Tel.: 351 914 413 804

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