Summer 2020

Living Science

Woman in lab wearing orange T-shirt that says "1411 Species of Bats (October 2019)." An inflatable black novelty bat hangs from the ceiling nearby.
Bat expert Amy Wray, a doctoral candidate in wildlife ecology, is pictured in a research lab in Russell Laboratories at UW–Madison. Photo: Jeff Miller


It would be hard to find someone more enthusiastic about bats than Amy Wray. She’s so fascinated by these winged mammals that she’s devoted her academic career to studying and understanding them.

A doctoral student of wildlife ecology, Wray’s expertise lies at the intersection of wildlife diseases and the food web. Her master’s thesis research focused on the feeding habits and pathogens of common vampire bats in Guatemala, and now she’s using next-generation DNA sequencing and other methods to study the diets of insect-eating bats in Wisconsin.

One thing Wray has come to understand through her research is that bats play a vital role in our ecosystem. It wouldn’t function well without them. Despite such a crucial benefit, bats still spook some people out.

Some of that fear stems from bats’ reputation as disease carriers. This concerns Wray, especially in a post–COVID-19 world, because it could lead to needless harm to bats when many species are already struggling with habitat loss and diminished food supply, among other challenges. Here she offers answers to frequently asked questions about bats, their role (and that of humans) in viral outbreaks, and how conservation can be a solution.

Did SARS-CoV-2, the virus that causes the disease called COVID-19, come from bats?

At this point, the origin of SARS-CoV-2 is not totally clear, but several studies have shown that the virus is similar — though not identical — to a virus found in a particular species of horseshoe bat. It is possible that an intermediate host (another animal species, potentially an animal that comes into contact with humans more frequently) also could have been involved.

SARS-like coronaviruses have been most commonly detected among a few species in the horseshoe bat family (Rhinolophidae), so called because of their uniquely shaped noses, which help them use a special type of echolocation. An interesting note on bat evolution: All eight of the bat species found in Wisconsin are in the family Vespertilionidae, which last shared a common ancestor with horseshoe bats around 60 million years ago.

Disease spillover from wildlife is not the fault of the animals. Rather, it is often a result of various human activities. For example, the animal trade brings together wildlife and livestock species that may previously have never been in contact with each other, which can create a situation where a new disease is likely to emerge. Additionally, the destruction or degradation of habitat can cause wild animals to become stressed, to change their movement patterns, or to come into contact with humans more frequently, which leads to an increased risk for the emergence of zoonotic diseases (those that can spread from animals to humans).

Why do so many diseases come from bats?

There has been a long-standing debate in biology over whether bats are special in their ability to host viruses and other pathogen-causing microbes. When bats fly, their body temperature increases, so some studies have suggested that flight may limit infections in a way that is similar to the fever response in other mammals. Other studies have suggested that bats might have a unique immune system.

Bats are a super diverse group (there are an estimated 1,411 species as of October 2019), so perhaps it seems like a lot of emerging diseases come from bats simply because there are many different types of bats. A recent study has shown that bats don’t actually host more human-infecting viruses than other mammals after accounting for the number of bat species. Also, a lot of research that involves pathogen discovery — including studies searching for novel coronaviruses — tends to focus on bats, so there could be an element of research bias in terms of which animals are more studied.

Can I get COVID-19 from a bat?

Bats do not spread COVID-19, and people are essentially always infected by other people rather than through contact with animals. There is a key difference between the animal origins of a zoonotic virus and the mechanism underlying how that virus spreads in human populations. So, no matter where COVID-19 came from originally, evidence shows that at this point it is being spread by people, not by bats or any other animals.

Nonetheless, it is generally a good idea to leave wildlife alone and avoid direct contact with wild animals for the benefit of their health as well as ours. When you see scientists practicing good use of personal protective equipment by wearing masks and gloves while handling wild animals, we do this partly because it keeps samples from being contaminated and keeps us safe from the animals. But just as important, this practice keeps the animals safe from us.

What should I do if I find a bat in my house?

In North America, summer is upon us, and it’s a common time of year for people to see bats flying around in the evening or to find bats in their houses. If you do find a bat in your house, do not touch or handle it. Instead, try turning off the lights and opening a window, and it will probably leave on its own. There are many ways to safely remove or exclude unwanted bats.

In Wisconsin, hibernating bats are listed as threatened species at the state level, and northern long-eared bats are listed as a threatened species by the federal government, so harming or harassing bats is not only inhumane and unnecessary but also illegal in certain areas.

Should I be afraid of bats or try to get rid of them?

There is no reason to fear bats! It’s important to understand that misinformation regarding bats as disease reservoirs can pose direct threats to bat conservation. There is strong evidence that harming bats does not reduce the likelihood of disease risk and can actually be counterproductive.

Like most mammals, bats can carry diseases like rabies — although it is uncommon — so they should be handled only when absolutely necessary and only with proper precautions. When bats are left alone and undisturbed, they are not dangerous. In fact, hibernating bats in North America have experienced drastic population declines due to a fungal disease called white-nose syndrome, which was probably introduced to their habitat by humans.

Why should we be concerned about declining bat populations? If so, what can be done to help them?

Many bat species provide ecosystem services, such as pollinating plants, reducing crop pests, and dispersing seeds, so protecting them has many benefits for humans and for the environment. Conservation of bats and other wildlife offers an effective and scientifically supported solution for reducing the risk of zoonotic disease emergence.

A great way to help our bat friends right now is to share the message with others that bats should not be blamed for COVID-19. You can do this armed with knowledge. Learn the science behind preventing disease spillover from bats. This free downloadable textbook contains detailed information about how human activities affect bats and includes a chapter on zoonotic viruses and bat conservation.

For bat enthusiasts of all ages, excellent interactive lessons and activities are available via TED-Ed, Project EduBat, and The Bat Squad, and you can spy on captive bat colonies through livestream videos of flying foxes and other bats. You can also help your local bats directly by planting a bat garden or installing your own bat house.

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