Mosquito Eating in Bats

8/9/18
By Merlin Tuttle

For decades, bat biologists have debated the extent to which bats prey on, and potentially reduce mosquito populations. However, recent research suggests bats may be eating far more mosquitoes than yet suspected. Amy Wray and associates (2018) relied on newly refined techniques that provide greater sensitivity. In their paper, titled “Incidence and taxonomic richness of mosquitoes in the diets of little brown and big brown bats,” they reported that these common species eat a greater variety of mosquitoes, and catch them more frequently than previously suspected.

A little brown myotis (Myotis lucifugus) in Wisconsin. Just one of these bats can catch 1,000 mosquito-sized insects in a single hour.

They tested guano samples from 22 locations in a range of habitats, across the State of Wisconsin, from May 17 through July 29. Seventy-two percent of little brown myotis (Myotis lucifugus) samples contained mosquitoes representing 15 species, more than twice as many as big brown bats (Eptesicus fuscus). But even the larger big brown bats, previously thought to feed mostly on beetles and moths evidenced mosquito-eating in 33 percent of samples. Frequency of mosquito-eating remained constant throughout the active season in big brown bats but declined slightly in little browns.

Little brown myotis (Myotis lucifugus) from Tennessee.
A third of big brown bats (Eptesicus fuscus) in Wisconsin fed on mosquitoes.

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Bat Flash! Smithsonian Promotes Misleading Virus Hunter Claims

By Merlin Tuttle
8/3/18

 

The July 11, 2018 edition of Smithsonian.com contains another highly misleading story on virus hunters protecting us from pandemics. The story by Katherine J. Wu is titled, “A Never-Before-Seen-Virus Has Been Detected in Myanmar’s Bats.” Wu claims that to prevent the next Pandemic, we need to pinpoint it at the source. She then reports that “researchers in Myanmar have hit pay dirt with a never-before-seen virus that infects wrinkle-lipped bats—a virus in the same family as the ones that cause SARS and MERS.”

Merlin with a young Black flying fox (Pteropus alecto).

After further extolling the virtues of virus hunting, she quotes Chelsea Wood, reportedly a conservation ecologist, as saying that, “Tropical rainforests [in particular] are just cesspools of viral diversity—the highest viral diversity on the planet.” The headline and rhetoric in this article sound more like grocery store tabloid writing than something one would expect from America’s leading institution of science.

This story is a complete contradiction of a paper by epidemiologists, Edward Holmes, Andrew Rambaut, and Kristian Andersen, titled “Pandemics: spend on surveillance, not prediction” which appeared in the Journal Nature on June 7, 2018. [1] Referring to virus hunting, they conclude that “given the rarity of outbreaks and the complexity of host-pathogen interactions, it is arrogant to imagine that we could use such surveys to predict and mitigate the emergence of disease.” They emphasize that broad surveys of animal viruses have little practical value when it comes to disease prevention. They conclude that such approaches are an extremely costly waste of limited public health funds and warn that “Trust is undermined when scientists make overblown promises.”

New viruses can be found wherever we look. Many are innocuous or even beneficial, [2]  including some that are closely related to deadly ones. [4] The number of viruses found in bats is not necessarily indicative of risk. [5] Nevertheless, promoters of virus hunting make low risks seem imminent and extreme. And since few people understand bats or viruses, the combination is ideal for manipulation used to justify outrageously large misappropriation of funds. [1]

Historically, bats have an outstanding track record. They rarely transmit disease to humans, even where millions closely associate with people in cities. [3] Yet virus hunters are creating a self-perpetuating cycle of fear that threatens their future. That people seldom protect, and often kill animals they fear, especially in the case of bats, is historically well documented.

The Smithsonian.com story follows a familiar virus hunter pattern of promotion. It begins with a scary, headline-grabbing title, followed by speculation of potentially great danger to be prevented, and appears to be confirmed by reported-to-be-independent colleagues. At the end, they add an apparent disclaimer. This one is typical, stating that viral discovery studies can lead to demonizing animals, noting that, “Just because they carry nasty diseases doesn’t mean we should kill these species.”

It’s time to end costly virus hunts that squander public health resources and needlessly create fear of already declining, but ecologically essential bats. As our nation’s highest institution of science, when the Smithsonian publishes misinformation it is particularly damaging.

TAKE ACTION!

Our combined voices can make a difference. Choose any or all means of contact to reach out to the staff at Smithsonian.com and politely share your opinion in your own words. Editors do take notice. Remember, your response can be very simple such as, “I don’t appreciate speculation that creates needless fear of bats.” Editors just need to know you like or dislike an article in order for you to have impact. It’s numbers that count. Bats need all of you!

 

This series of photos show me radio-tracking a bat to its roost in a giant, hollow tree in the Smithsonian’s Barro Colorado Island rainforest, than squeezing inside to photograph the colony. If rainforests, and the bats that live there were truly “cesspools of dangerous viruses,” I should have died a horrible death long ago!

Little big-eared bat (Micronycteris megalotis) and Seba’s short-tailed fruit bat (Carollia perspicillata) roosting in the hollow tree.

 

 

References

[1] E. Holmes, A. Rambout and K. Andersen, “Pandemics: spend on surveillance, not prediction,” Nature, no. 558, pp. 180-182, 2018.
[2] J. Enriquez and S. Gullans , ““Viruses, the Roadrunners of Evolution”,” in Evolving Ourselves, New York, NY: Penguin Group, 2015, pp. 99-103.
[3] M. Tuttle, “Fear of Bats and its Consequences,” Journal of Bat Research and Conservation, vol. 10, no. 1, 2017.
[4] M. Miranda and N. Miranda, “Reston ebolavirus in humans and animals in the Philippines: A review.,” Journal of Infectous Diseases, vol. 204, no. 3, pp. S757-S760, 2011.
[5] K. Kupferschmidt, “Bats may be carrying the next SARS pandemic,” Science, 2013.

 

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Epidemiologists Acknowledge Virus Hunting as a Costly Waste

By Merlin Tuttle
6/15/18

Leading epidemiologists are finally acknowledging that the recently huge expenditures for virus hunting (mostly focused on bats) have little practical value in disease prevention. The June 7 issue of Nature contains a key paper titled, “Pandemics: spend on surveillance, not prediction.” In it Edward Holmes, Andrew Rambaut, and Kristian Anderson combine their expertise to advocate a much-needed change of course in prevention of viral transmission from animals to humans, one that may also considerably brighten the future of bats.

They emphasize that broad surveys of animal viruses have little practical value when it comes to disease prevention and warn that “Trust is undermined when scientists make overblown promises about disease prevention.” They “urge those working on infectious disease to focus funds and efforts on a much simpler and cost-effective way to mitigate outbreaks—proactive, real-time surveillance of human populations.”

Bats have an exceptional record of living safely with humans. But, they have been disproportionately searched, and victimized by virus hunter speculation, apparently because they are unpopular and easy to sample. This is an Angolan free-tailed bat (Mops condylurus), a species targeted for eradication following premature speculation linking it to the 2014 Ebola outbreak.

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Bats and Chocolate Production

By Merlin Tuttle
6/6/18

While conducting her Ph.D. thesis research, Bea Maas and her team (Maas et al. 2013) collected data that would surprise even her. When insect-eating bats and birds were excluded from cacao trees in Sulawesi, Indonesia, the crop yield fell by 31 percent. And when she compared losses due to night versus daytime exclusion, bats versus birds, she discovered that bats accounted for 22 percent of the prevented losses.

A control site in the same study (poles without netting).

To obtain such data, Bea selected 15 plantations where she enclosed 120 cacao trees in 60 exclosures (like huge, mesh cages) constructed of nylon mesh. There were four exclosure treatments per plantation, one daytime, one nighttime, one day and night, and one always left open as a control.

A bat/bird exclosure in Sarawak, Indonesia, built with bamboo poles and commercial nylon monofilament netting with a mesh size of 2 x 2 cm. These were opened and closed like curtains daily.

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Thanks to Mongabay for Balanced Nipah Reporting

By Merlin Tuttle
5/31/18

We greatly appreciate Mongabay for its handling of the Nipah virus outbreak in Kerala, India. Its story, “Nipah infection in Kerala: Don’t blame the bats alone; improve public health,” appeared on May 30, authored by Haritha John and Gopikrishna Warrier. Needless alarm was avoided by balanced reporting. As so often is the case, the rarest threats make the biggest news. Fortunately, in this instance, the news was accurate, so did not cause needless panic.

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Bat Flash! Respond to Reuters News Release Blaming Bats for New Ebola Outbreak

By Merlin Tuttle
5/15/18

 

I share Benoit Nyemba and Fiston Mahamba’s concern regarding a potential resurgence of Ebola in the Democratic Republic of Congo, as Reuters News reported on May 8. Nevertheless, continuing to blame bats as the source is likely to reverse conservation progress essential to  ecosystem health (Lopez-Baucells et al. 2018) and delay successful Ebola prevention. Understanding the true source is essential.

A male straw-colored fruit bat (Eidolon helvum). This is the species that was first erroneously blamed for infecting the two-year-old toddler identified as the index case that triggered the 2013-2014 Ebola outbreak. In the end no one could explain how a bat that never enters buildings and has a three-foot wingspan could have contacted a toddler without anyone knowing about it!

Bats can indeed transmit deadly diseases like rabies and Nipah to humans, though transmission is exceedingly rare and easily avoided. In the case of Ebola, bats have been too easily assumed guilty. A wide variety have been tested at outbreak locations. But, “Ebolavirus has yet to be isolated from bats, and no direct evidence links bats to Ebolavirus infection in humans.” (Spengler et al. 2016) Virologists still know “nothing about where it comes from and how it causes outbreaks.” (Kupferschmidt 2017).

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Success in Panama!

During both weeks of our workshops, we encountered periodic rain showers, keeping the normally hot, dry-season temperatures far more comfortable than anticipated. The downside was that we had poor netting results on three nights during the second week. We shared the forest with some interesting characters, such as a black jaguar, which fortunately left us alone, though it likely observed our activities. This one was photographed on a trail camera near one of our netting sites.

 

We set up a triple-high mist net almost every night, both weeks.

Departing to net bats over the nearby river. Daniel Hargreaves is carrying the triple-high net rig in the red bag. His team of skilled instructors from the U.K., Steve and Fiona Parker and Daniel Whitby, were superb.

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Bat Flash! Encouragement for Positivity in Cambodia

This powerful article in Southeast Asia Globe, by Claire Baker-Munton, on the value of artificial bat roosts in Southeast Asia deserves much praise. With the help of Merlin’s photos, this article clearly promotes a better understanding of bats and their values. At a time when so many media headlines are attempting to grab readership by speculating potential linkage of bats to scary diseases, positive stories like this are crucial. In reality, as Claire points out, Cambodians have found bats to be highly valued neighbors.

TAKE ACTION!

Choose any or all means of contact to reach out with your praise and encouragement on behalf of bats.

 

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Wildlife and Wind Farms: Conflicts and Solutions Book Review

Wildlife and Wind Farms: Conflicts and Solutions
Book Review by Merlin Tuttle
1/8/18

 

Wildlife and Wind Farms, Conflicts and Solutions, Volume 2, provides a summary of current conflicts and solutions involving the rapid growth of wind farms and their impacts on wildlife. Chapters by leading experts cover topics from turbine siting and mortality monitoring to, statistical evaluations and mitigation.

This is the second of two volumes, both edited by M.R. Perrow. They are thorough and authoritative, an important resource for professionals concerned with wind energy impacts on wildlife. Unfortunately, this is a complex subject, and industry has been slow to adopt many of the remedies reported. Issues for birds and bats differ significantly and typically require different solutions. This review emphasizes those involving bats.

Ridgetop turbines in West Virginia.

Early investigations often failed to account for searcher detectability or scavenger removal rates when calculating wildlife fatalities at wind farms. Such problems were exacerbated by long intervals between searches, during which most corpses were removed by scavengers or arthropods. Small corpses can virtually disappear to human view in even a few inches of vegetation, and most of a night’s kill can be removed by scavengers within hours, depending on local circumstances. Trained dogs have performed far better than humans in searching for kills, but few are used. Fatality detection is complicated and often debated.

 

The impact of scavenger removal is difficult to accurately document. Depending on local scavenger faunas, removal rates can vary greatly. Scavengers may also take time to discover a new food source, causing removal rates to change from week to week or year to year.

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Bat Flash! Respond to Misleading Attempt to Encourage Fear of Bats 12/1/17

By Merlin Tuttle
12/1/17

The November 23, 2017 issue of THE CONVERSATION lures readers with an important sounding, bat-friendly title, “Can bats help humans survive the next pandemic?” However, two-thirds of the article is devoted to promoting fear instead of progress and is based on questionable sources. This is particularly disturbing given the publication’s stated objective—“Fight for Truth in Journalism.”

This story is a simple repeat of close to a decade of often exaggerated speculation attempting to link viruses found in bats to transmission of scary but relatively rare ones like SARS and MERS to humans. Documented transmission of any disease from bats to humans remains exceedingly rare. And no one has successfully shown transmission of SARS or MERS from bats to other mammals. Dromedary camels are now well known to have been the source of MERS in humans for decades, likely longer.

Villagers harvesting bat guano from Rakang Cave in Thailand. For as long as anyone can remember no unusual illness has occured, one of many similar contradictions that virologists forecasting world pandemics from bats cannot explain.

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