Bat House Warnings – A Reality Check

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.

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Inspiring Bat Conservation Through Photos

4/9/2021

By Teresa Nichta

The Bat Scan Project provides photo documentation, enabling a growing number of conservation projects and exhibits worldwide to share the values of bats. These photos are also heavily used in children’s books, school reports, and in both scientific and popular publications. For example, the Smithsonian’s book, BATS: An Illustrated Guide to All Species, exclusively relied on nearly 400 of Merlin’s photos.

We’re delighted to share a few highlights from recent use.

A Mexican long-tongued bat (Choeronycteris mexicana) pollinating agave flowers (Agave palmeri).
A California leaf-nosed bat (Macrotus californicus) catching a cricket.
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Comments on World Health Organization’s COVID-19 Report

The World Health Organization’s recent report on COVID-19 speculates a bat origin. However, its findings are seriously flawed and questioned by the Biden administration according to the Wall Street Journal. Former CDC Director, Robert Redfield, in his CNN interview, still believes it escaped from a lab in China. The origin clearly remains unresolved.

A review of scientific literature reveals that SARS-CoV-2, the coronavirus that causes COVID-19, has not been found in bats, and there are no reports of transmission from a bat to a human.

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Severe Weather Takes Heavy Toll in Texas

By Merlin Tuttle
3/2/21

Given overall warming trends, we weren’t surprised to see some 70 to 80° F days in January and February of 2021. But that hardly tells the full story!

Beginning on February 10th, historically low temperatures were recorded across Texas. For eight consecutive days (February 10–18), the temperature hovered between 37° and 9° F with six inches of snow on the ground in Austin, Texas. The first reasonable feeding opportunity for bats likely didn’t occur before the 21st.

The last similar event occurred 32 years ago in 1989. In a 9-day period (December 16–24) the daily temperature ranged from 51 to 4° F but remained below freezing for only two days versus seven in 2021. Fewer people were concerned in those days, but at least hundreds of killed bats were reported.

Brazilian free-tailed bats about to emerge from their day roost in a bridge crevice in Austin, Texas.

The recent event, Winter Storm Uri, created a disaster for overwintering Brazilian free-tailed bats (Tadarida brasiliensis). Encouraged by warming trends, more and more bats have remained in their summer roosts year-round instead of migrating south for winter. In recent years, hundreds of thousands have overwintered in bridge crevices of Central Texas, especially in the Austin area. Additionally, over the last four decades, an estimated 1,000 more annually have remained in Bracken Cave.

Unlike many other temperate-zone bats, Austin’s free-tails are not true hibernators. They do store fat in the fall and can survive for more than six weeks without feeding when roosting at 41° F. In Central Texas, they emerge and successfully feed when evening temperatures are 50° F or above, and in traditional winters they seldom would need to wait more than 10 days between feedings.

To survive for eight days with average temperatures well below freezing would be an extreme challenge. Bats have the largest surface area per volume of any warm-blooded animal, and active free-tails maintain body temperatures of roughly 102° F. Following the recent weather crisis, just warming up to go hunting was undoubtedly prohibitive for many, and it’s difficult to imagine that the insects the bats depend on for food would have been immediately abundant. Even though daytime temperatures averaged 78° F over four consecutive days beginning on February 21st.

Many concerned Austinites wondered why accumulations of dead and dying bats steadily grew through at least the 25th, despite the return to warm weather. The answer is two-fold. Many bats likely were still alive but too weakened to go hunting. Some of those may take a week or more to die. Also, those that literally froze to death could take weeks to fall from their roosting crevices. Tendons in their toes are designed to automatically lock the bats’ claws firmly to the roosting crevice until consciously released. Thus, a bat may hang in place long after its death

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Bat Flash! Help John Oliver Put Bats in Perspective

The Last Week Tonight with John Oliver February 15th episode shared misguided speculations about bats. Here is Merlin’s public letter to John Oliver. We don’t have his email address, so we’re counting on you to help get his attention. No shade, John, we understand the topic is muddy. We simply want the opportunity to set the record straight!

Contact information and action steps are listed below.

Dear John,

Given your reputation for integrity and fearless candor, several of your loyal followers have asked me to help you better understand disease risks from bats. Why me? Because, as one of the world’s most experienced bat researchers, I’ve handled hundreds of species worldwide for 60 years, often surrounded by millions in caves. I’ve also led successful conservation efforts internationally for more than 40 years. My experience and photographs are used worldwide, including in National Geographic articles, to share the truth about bats through my organization, Merlin Tuttle’s Bat Conservation. Here’s a clip from my appearance on David Letterman decades ago; I have been leading efforts to educate humans about bats my entire career.

I, and hundreds of others who study bats, have spent whole careers working with them unprotected against any of the so-called emerging diseases about which we’re now warned. And we’re still healthy. We’re also aware that millions of people visit and work in caves annually without causing disease outbreaks.

Thus, we question the sanity of warnings of extreme risks to visitors of tour caves where a bat could purportedly cause a deadly pandemic by defecating on them. There is no proof that such an event has ever occurred. And warning of the possibility is like warning of death from a falling spacecraft, possible but extremely unlikely.

I appreciate your mention of the far greater risks from industrial meat production and your comments on the essential contributions of bats to a healthy planet, but this is not enough to cultivate understanding and put risks in perspective. For the record, unlike rodents who are overpopulating due to the loss of predators, bats are extraordinarily vulnerable to extinction and already in alarming decline.

Exaggerated fear is the greatest cause of human intolerance and killing of bats. Unfortunately, sensational speculation, linking them to scary diseases, sells headline media stories and large grants. Virus hunting, typically linked to bats, has been shown to be an ineffective means of pandemic prevention. However, because bats are the easiest mammals to sample, and have few defenders, they have become tempting victims. Your guest failed to mention that, for anyone who simply doesn’t handle bats, the risk of contracting any disease from one is minuscule. In fact, millions of bats share cities with people from America to Africa and Australia without causing disease outbreaks. As our human population continues to expand, we inescapably must learn to live in harmony with nature.

Although well-intended, the following documented points are too often distorted or ignored in sensational media coverage. I’d be more than happy to assist you and your staff in balancing the story.

  • Bats harbor no more viruses than other animals 1.
  • Claims of disease from bats are often based on poorly supported speculation 2.
  • Claims of 96% genomic similarity between viruses are meaningless and misleading 3,4.
  • Promises that can’t be kept are misdirecting billions of dollars to virus hunting that is counterproductively biased toward bats and better spent on other health priorities 5,6, 7.
  • Bats have an undeniable history of living with humans without causing disease outbreaks 8.
  • There is a long history of lucrative, but exceptionally harmful, exploitation of disease exaggerations against bats 9.
  • Fear of bats leads to intolerance and killing 9,10.
  • Asking people to conserve bats because they are beneficial, while failing to counter exaggerated fear, is unlikely to improve conservation success 10.
  • Ebola was first speculated to come from fruit bats, then insectivorous bats, but more recently it was admitted that no source has been found despite extensive efforts 11, 12.
  • It cannot be stated strongly enough that Ebola, SARS, MERS, and SARS-CoV-2 have not been isolated from a bat despite frequent attempts.

Also, here’s a recent video sponsored by the U.S. National Park Service about putting bat fears in perspective. Thank you for your time, I hope to hear from you.

Kindly, 

Merlin

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Bat Flash! Where Did COVID-19 Really Come From?

01/28/21

By Merlin Tuttle

USA Today’s January 17 story, Where did Covid-19 come from? leads with the following statement “The coronavirus that conquered the world came from a thumb-sized bat tucked inside a remote Chinese cave. Of this much, scientists are convinced.”

Deep in the story, they quote virologist John Connor at Boston University, saying ‘It looks like it’s a bat-derived virus, and there’s a big question mark after that.’ Fellow virologist, Charles Chiu, an expert in viral genomics at the University of California—San Francisco, is additionally quoted as saying ‘It may also have emerged from any setting in which people come into contact with animals, including farms, pets or zoos.’

Clearly, all scientists are not convinced that this virus came from bats, not even those interviewed for this story. The disproportionate focus on bats as the source of the COVID-19 pandemic is based on poorly supported speculation that harms conservation efforts worldwide.

Intermediate Horseshoe Bat (Rhinolophus affinis)

One of the most cited studies accuses bats of hosting more viruses than other mammals. Yet, the authors of this study surveyed twice as many bats as all other mammals combined. More inclusive research suggests that bats do not harbor more viruses than other animals.

New viruses can be found wherever we look, so it is not surprising to find more in the animals that are predominately searched. The claim that the SARS-CoV-2 virus, the source of the COVID-19 pandemic, shares 96% of its genetic material with a coronavirus found in a horseshoe bat is meaningless. We ourselves are 96% genetically similar to chimpanzees which we easily recognize as non-human.

Current biases threaten the survival of bats that have undisputed value and are already in alarming decline. They also harm science credibility and misdirect the search for zoonotic reservoirs by focusing disproportionately on bats. Despite relentless searching and endless speculation, there is no documentation that SARS-CoV-2, SARS, MERS, or Ebola viruses have been found in, or transmitted from a bat to a human.

As noted by Yong-Zhen Zhang and Edward Holmes, it is critical that coronavirus surveillance should include animals other than bats. Blaming bats based on one-sided searches is premature and misleading.

 TAKE ACTION!

Our combined voices can make a difference. We invite you to politely share your opinion in your own words with the editors. You may find our resources, Give Bats a Break and Good Intentions Can Still Leave a Bad Taste, additionally helpful in composing your personal reply and discussing these topics with others. Editors do take notice. Remember, your response can be very simple such as, “I don’t appreciate misleading speculation that perpetuates needless fear of bats.” Editors just need to know you like or dislike an article for you to have an impact.

It’s numbers that count and bats need all of you! Tell a friend about bat values and how they can help.

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Bat Flash! NatGeo’s “Virus Hunters” Spreads Groundless Claims About Bats

11/2/2020

By Merlin Tuttle

I viewed the National Geographic documentary series titled, “Virus Hunters,” with substantial disappointment. Warnings of growing reliance on bush meat and industrial farming were justified. However, coverage of wildlife too often exaggerated risks from bats. 

Bats are exceptionally easy to trap in large numbers, have few defenders, and are easily misunderstood. This makes them prime targets for scary speculation that is exceptionally lucrative in gaining media readership and unprecedentedly large grants. And unfortunately, the opinions of leading virologists who doubt that virus hunters can predict or prevent pandemics were left unmentioned.

The 2017 study that reported more viruses in bats than in other mammals sampled nearly twice as many bats as all other mammalian orders combined. Since most viruses have yet to be discovered, new ones can be found wherever we look. And because bats are an ancient group of mammals, it is not surprising that they sometimes host ancestors of modern species. 2020 study, concluding that bats harbor no more viruses than other animals, has been largely ignored.

Hundreds of thousands of Straw-colored fruit bats (Eidolon helvum) beginning their evening departure from a city park in Ivory Coast, Africa. Cities often provide the only homes safe from commercial hunters who sell them for people to eat. Despite such large numbers having lived in close association with humans throughout recorded history, they have not caused disease outbreaks. Their remarkable safety record casts grave doubt on recent speculation of their being dangerous carriers of disease.

Documented transmission of any disease from a bat to a human is exceedingly rare, and the risk is near zero for anyone who simply does not handle them. Hundreds of thousands of bats live in city parks across Africa. Yet there are no verified cases of Ebola transmission, despite huge efforts to find such an association. In fact, despite repeated assertions, there are no documented cases of Ebola, MERS, or SARS-CoV-2 viruses ever having been found in a bat, much less transmitted from a bat to a human. In truth, bats have one of the world’s finest records of living safely with humans. For example, in Austin, Texas countless thousands of visitors have safely viewed the spectacular emergences of 1.5 million free-tailed bats for decades without a single incident of disease transmission.

I have safely studied bats for more than 60 years, including publishing five articles in their defense in National Geographic. It is sad indeed to see bat survival threatened due to the same, traditionally respected, organization spreading groundless claims that bats can defecate deadly viruses by simply flying overhead. People seldom tolerate and often kill animals they fear, and none are more vulnerable than bats. Please, in your future coverage of Virus Hunters, put bat risks and benefits in perspective. The irresponsible spreading of falsehoods needs to stop.

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Timely New Children’s Book

9/3/2020

By Merlin Tuttle

Life Upside Down

Australia’s Grey-headed flying-foxes

Leading wildlife photographer and conservationist, Doug Gimesy, has teamed up with award-winning media graphic artist, Heather Kiley, to produce an outstanding introduction to the upside-down world of grey-headed flying foxes. Through stunning photography, simple text, and eye-catching design, this book provides a timely introduction to some of the world’s most frequently misunderstood and intensely persecuted animals.

Victims of misunderstanding and mass eradication attempts, Australia’s flying foxes now survive only as tiny fractions of former numbers. Forest clearing has left them homeless and starving. Countless thousands have been killed in mass shooting campaigns, electrocution grids, and flame thrower attacks on their roosts, known as camps. Remnant survivors are now forced to live in cities where they are needlessly demonized as carriers of dreaded diseases, despite a long history of living safely with people or subjected to attempts of forced eviction with nowhere else to go. Welcomed honeybees, dogs, and especially humans are far more dangerous! Moreover, large numbers of flying foxes are essential to reforestation and the survival of much-loved animals such as koalas.

Readers of Life Upside Down will be introduced to the real world of flying foxes as safe and invaluable neighbors and learn how they can be helped. This full-color, large-format, 48-page book is available in hardcover for $19.95 at Australian Geographic or at Book Depository.  

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Costa Rica’s Bat-Friendly Hotel

3/11/20

By Paula Tuttle

Merlin and I recently spent an especially productive week promoting bat conservation at the Harmony Hotel in northwestern Costa Rica. Merlin’s lecture, introducing the many values of Costa Rican bats, attracted a large and enthusiastic audience that included both hotel guests and community members.

Thanks to the owner’s passionate commitment to a healthy, sustainable environment, the hotel is a wildlife oasis in the midst of the small town of Nosara. Wherever possible, a lush profusion of native vegetation has been restored or introduced, serving as a magnet for animals, from howler monkeys, coatis and margay cats to large iguanas and an impressive variety of bats.

We quickly recorded more than a dozen bat species, belonging to five families, and introduced them to appreciative staff and guests. In fact, the proximity of multiple species posed the biggest challenge to use of a bat detector. The hotel may soon attract even more bats, as it intends to put up bat houses.

We were especially encouraged to learn of all the hotel’s progress toward environmental sustainability while maintaining top quality. The staff were outstanding. The food was healthy and delicious, and we thoroughly enjoyed the two evenings spent introducing the owners’ family and friends to the diverse array of bats found in their own yard.

Merlin has prepared a program on Costa Rican bats for the hotel to share with guests and in local schools, and we look forward to further collaboration.   

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Thai Adventures Part 4: Khao Chong Pran

2/19/20

By Merlin Tuttle

For me, our trip highlight was the visit to the Khao Chong Pran Cave in Ratchaburi Province. Nearly 40 years ago Buddhist monks who owned the cave had asked my advice. Their monastery relied on bat guano fertilizer sales for support. But in 1981 production was plummeting. Of course, and the monks wanted to know why.

Merlin and Surapon reminiscing about their first visit to Khao Chong Pran Cave nearly 40 years earlier.

Before dawn the next morning, my then young field assistant and interpreter, Surapon Duangkhae, and I discovered poachers using large fish nets to capture bats at the cave entrance. They were selling them to local restaurants. We hired two of the poachers to help us document the extent of the problem, then advised the monks to hire a game warden to protect their bats.

Merlin answering game warden’s questions in 1989.
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