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.

 

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.

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.

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.

We installed this bat house, donated by BatsBirdsYard.com, for testing in a central Texas pecan orchard. Nut growers increasingly are using bat houses in pest management.

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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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