A Myth is Born – Do Bats Eat Mosquitoes

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Robert Pavlis

I am sure you have heard the stories; a small bat can eat 1,000 mosquitoes a night. This idea is so well known that many people have put up bat houses to attract this animal even though most people hate bats. I guess they hate mosquitoes even worse.

It all makes so much sense. Bats fly at night eating insects. Mosquitoes come out at night to hunt us. Why would bats not eat this plentiful food? And then there is the science; scientists studied bats and determined they could eat 1,000 mosquitoes a night.

In this post I will look at this myth and explain how the myth originated. It is quite rare for me to be able to know how a myth starts, but in this case it’s fairly clear.

A Myth is Born - Do Bats Eat Mosquitoes
A Myth is Born – Do Bats Eat Mosquitoes, little brown bat, photo by SMBishop

Science, Bats and Mosquitoes

In 1960 a paper was published called, The Echolocation of Flying Insects by Bats. This study found that a bat could eat 10 mosquitoes per minute or 600 an hour, which eventually got reported as 1,000 per bat, every night.

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This science seemed to prove that bats eat a lot of mosquitoes each night, but the conclusion was flawed.

First of all, the bats were released in a closed room, and given only mosquitoes to eat. Well, any half intelligent bat will eat whatever it’s given.

No part of this study looked at what bats do outside of the lab.

The individual bats were selected because they were proven hunters. Remember that the scientists were interest in figuring out how bats find their food. It had noting to do with their diet.

Only one bat captured 10 per minute. Others were as low as 2 per minute. This is a common mistake made by reporters of scientific news – the best case value was reported, not the most realistic value.

These mistakes led the general public to start reporting that bats eat a lot of mosquitoes, as many as 1,000 a night, and that they are good at controlling populations. Nothing in this statement is supported by the above mentioned study, nor did the study reach this conclusion. It was the writers reporting on the study that made these claims – not the scientists.

More Science

There has not been a great deal of research on this topic, but there have been some good studies.

One study looked at the “taxonomic richness of mosquitoes in the diets of little brown and big brown bats“, which are common in the US and Canada. They looked at the DNA of bat fecal material to determine which species of mosquito were eaten. Mosquitoes were detected in 72% of samples from little brown bats and 33% of samples from big brown bats. The number of mosquito species eaten by little brown bats was also higher than for big brown bats.

In summary, brown bats do eat mosquitoes, but not all colonies eat mosquitoes. Small bats are more likely to eat mosquitoes and tend to feast on a larger number of species.

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An Australian study looked at fecal mater from five local bat species. A total of 40 insect species were detected and moths were the most prominent. Mosquitoes were only detected for two of the five species. They concluded that smaller bat species are more likely to eat mosquitoes, and that not all species of bats eat mosquitoes. “There is a species-specific relationship between bats and their preferred meal.”

Little brown bats observed in a barn in Alaska showed that bats do use echolocation to find mosquitoes and that the mosquitoes “did not show any defensive behavior in response to approaching bats.” That is why devices that mimic bat sounds don’t work for keeping mosquitoes out of the backyard.

Another study looking at little brown bats in Alaska found that only 2% of their diet was mosquitoes.

A study of the little brown bat in New Hampshire found that when mosquitoes were very plentiful, bats consumed significant numbers.

Bat house
Bat house

A study in Sweden looked at the northern bat and found that, “In summer, northern bats rely heavily on mosquitoes and other dipteran insects, particularly in the north where summer nights remain light, and most feeding takes place in forested areas. In the south, the same species of bat feeds over lakes and farmland, and their diet varies accordingly, including dung -beetles, moths, and caddis flies as well.”

Do Bats Eat Mosquitoes?

There are 1,000 species of bats in the world and very few have been tested to see what they eat. Some don’t eat insects at all, but even the ones that do, have species-related diets. You can’t reach any conclusion about all bats. The right answer is, some do and some don’t, and this changes based on the environment.

Smaller bats are more likely to eat mosquitoes than larger ones.

Bats are opportunistic. When they are hungry, they eat what is available. Mosquitoes don’t take evasive action like other insects, so mosquitoes are easy to catch. Unfortunately, they are very small and so a bat might chase a larger more difficult prey in order to get a decent meal.

When mosquitoes are plentiful, as is the case in Northern Sweden, bats eat more mosquitoes. When mosquitoes are less plentiful they eat fewer and rely mostly on beetles, wasps, and moths.

We can say some bats eat mosquitoes and in some cases mosquitoes make up a good part of their diet. The often quoted “bats eat 1,000 mosquitoes a night”, is not based on real world science and is a myth – in most cases.

Do Bats Control Mosquito Populations

Bat tower in Florida, built to control mosquitoes, photo by Ebyabe
Bat tower in Florida, built to control mosquitoes, photo by Ebyabe

Gardeners don’t really care if bats eat mosquitoes. What they want to know is, can bats control the mosquito population? Are bat houses a good way to keep them out of the garden?

The American Mosquito Control Association reports the following story, “During the 1920’s several bat towers were constructed near San Antonio, Texas, in order to help control malarial mosquitoes. Mosquito populations were not affected and the project was discontinued.”

Shelly Redovan, head of the Florida Mosquito Control Association, says, “the state of Florida has tried using bats to control mosquitoes. They tried bat towers, bat houses, and they were a dismal failure.”

The bat tower pictured here was built in Florida to control the mosquito problem. However, when the bats were put in, they supposedly flew away, never to return.

Mr. Tuttle, an expert and proponent of bat conservation, admits that, “simple provision of additional roosts should not be promoted as more than one step in the right direction toward solving mosquito problems. In some cases bat houses may help and in others, they may not.” There is no scientific evidence that bat houses reduce the local mosquito population by any significant amount. Any mosquitoes that are eaten are likely replaced from neighboring gardens.

Before setting up a bat house to control mosquitoes you should confirm that you have some of the smaller bats in the area and that they eat mosquitoes. It is much more difficult to get bats to inhabit a purchased bat house than is suggested by manufacturers of these homes. Putting up a bat house is a good idea; bats need all the help they can get. Just don’t expect relief from the skeeters.

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

18 thoughts on “A Myth is Born – Do Bats Eat Mosquitoes”

  1. Responding to “Em” above. The author is correct in that the article argues much more than merely effectiveness of bat towers. It’s a decent article overall.

    However the article also makes a logical fallacy. The “fallacy fallacy” argues that something is not necessarily false simply because it has been poorly/incorrectly argued.

    To imply that bat roosts are not useful because bat towers failed is a “fallacy fallacy”.

    Why?

    Because bat towers are the “poor argument” the fallacy describes. Bats flew away because the towers were constructed with inadequate understandings of bat behaviour.

    So the only thing this example correctly illustrates is that a bat tower is a poor choice for a bat roost. Since the article is not about bat towers per se, this entire section should be removed from the article because it only misleads the reader with an inappropriate and fallacious example.

    https://yourlogicalfallacyis.com/the-fallacy-fallacy

    Reply
    • “To imply that bat roosts are not useful because bat towers failed” – my post does not say that.

      What I said was “Mr. Tuttle, an expert and proponent of bat conservation, admits that, “simple provision of additional roosts should not be promoted as more than one step in the right direction toward solving mosquito problems. In some cases bat houses may help and in others, they may not.” There is no scientific evidence that bat houses reduce the local mosquito population by any significant amount. “

      Reply
  2. If it has not already been mentioned, I don’t see bats being able to eat mosquitos at all as mosquitos have no use in flying as high as bats are seen to do as the mosquito’s food source is ground based. Also you don’t see bats flying single OR in large groups close to the ground. But then what are bats doing flying so high, where do they feed? Is the high flying possibly a gathering for procreation element and not feeding at all as I don’t imagine many of any type of insects fly that high???

    Reply
  3. All I can say is my story.
    When we moved into our home near the Withlacoochee River South Georgia, the mosquitoes were terrible. Our neighbors had bug zappers, we were troubled going from the car to the home and I would get attacked in broad daylight while mowing the lawn.
    We saw bats and I built a bat house.
    Now I can enjoy the river and outdoors.
    I just counted over 20 bats fly out at dusk. The highest I’ve conservatively estimated was 175. I’m a believer!

    Reply
  4. Just because science hasn’t done a peer reviewed study on something doesn’t make it untrue. It makes it an unproved hypothesis not a myth. Putting it in the realm of myth rather than unproved hypothesis makes me think you are a shill of something.

    Reply
    • “Just because science hasn’t done a peer reviewed study on something doesn’t make it untrue.” – correct and nobody is making this claim.

      However, claiming that something is true when it has not been proven does create a myth.

      Reply
  5. Thank you. This is the best (most balanced, sensible, and researched) article I have seen on whether bats eat mosquitoes to any significant extent. One is always being told to put up bat houses (and purple Martin houses, for that matter) to control mosquito populations. I have always been skeptical on both counts. I’m certainly not against putting up bat houses or purple Martin houses but mosquito control should not be the reason. I’ve always had the gut feeling that except perhaps in the case of very small bats, a mosquito is hardly worth it for a bat (or a purple Martin). It would be like humans trying to fill up on grains of rice eaten one by one. So as you say, perhaps some smaller bats may eat some mosquitoes, but for most bats it makes sense that mosquitoes are a very small part of their diet. Also, no-one mentions this – but mosquitoes tend to fly fairly close to the ground and close to vegetation. These are not good foraging places for bats, since bats catch their prey on the wing. The bats I see foraging at night are fairly high in the air and more out in the open. Ditto for purple Martins (and Martins are diurnal while mosquitoes are nocturnal, making their use as agents of mosquito control even more dubious!). In any case, I greatly appreciated this article and will refer others to it. Thank you!
    Nancy Greig in Houston, TX

    Reply
  6. I was just wondering how to get rid of the so called “Blind Mosquitoes”. I like to walk my dog early to late evening around the lake but these little bugs are so bad we can’t breathe, they fly up our nose,lol
    Any suggestions?

    Reply
  7. This issue with this article is that it states bats are ineffective at controlling mosquito populations because bat towers failed. This statement is immediately disproven when the article then states that bats did not stay in the towers, but instead vacated the area. Therefore the efforts were ineffective, not due to bats inability to impact mosquito populations, but due to the bat towers inability to maintain bat populations long enough for them to have any sort of impact.

    Reply
  8. The problem with bats controlling mosquito population is controlling the bat. We haven’t been able to domesticate or manipulate bats via habitats in any predictable way as Florida discovered.

    Ironically, Austin, Texas accidentally create a thriving bat habitat with a bridge they built over a river. It’s a popular local attraction to see the bats come out at night. I think it’s around 2 million of them. I also understand Austin has a very small mosquito problem. I cannot say the bat population is causal to this or not.

    Reply
  9. Tell that to the folks in Austin, Texas, who swear by their bat colony as mozzie deterrents. They claim the city is swept clean every night by the millions of bats that live under their bridge during summer (they migrate from Mexico). Maybe a bit of an exaggeration, but I know first-hand you can sleep screen-free 🙂

    Reply
  10. I think window screen (and screen clothing) are great inventions. No chemicals, stay on your screen porch (or in your suit) when they are active, respect their part in the ecology and protect yourself from any disease risk. Thanks for this wonderful article on so many levels. The bat tower was an icon of my childhood…I believe it was on Big Pine Key in Munroe county, FL, and we would go look at it and the tiny key deer when down there for weekends. It is a sad thing that my house in NS (named the Belfry for the LBBs that lived in the attic in abundance) now sits silent at dusk, when it used to be a favorite ritual to watch them leave and count them (65 at highest count, three years later none). None of the locals here seem to be concerned about their loss, any more than Floridians see mass extinction of mosquitoes for their convenience as a problem (all the native insectivore birds disappeared during my childhood, replaced by exotic species).
    The power of myth is something that cements humans in belief systems and cultural values, and I would love to see you explore that more. Also the “translation” of science by non-scientists is a fascinating line of inquiry. From money, to religion, to political party, we are all about myth. This is why science is so important…the search for facts and objectivity (an ideal). The problem with science is we have the myth that we actually know something about the world when the myth of the three blind men around the elephant more likely applies. There is so much more that is not studied than is, and we are currently dying in the face of no scientists that have been studying one new virus. I found the book Sapiens quite a read. Understanding the importance of myth and the hold we take upon it makes understanding this current era (and seemingly insane human responses to it) easier. Thanks again, love your work.

    Reply
  11. In Florida we have too many mosquitoes. They will bite any part of the day, especially when a gardener stirs the
    dense plants and bushes. Surprisingly, they don’t bite
    as much at night. Maybe they already got their quota. 🙂
    Our best defense comes from the trucks that spray the
    streets and planes that spray large open areas like swamps.
    For us gardeners I recommend wearing the long sleeve,
    cool-dri hoodies that are sold for sun protection.

    Reply

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