Why bats don’t get sick from the viruses they carry, but humans can

Bats are key pollinators and seed-spreaders, and keep pests away.

Livia O. Loureiro, University of Toronto

One of the first questions scientists ask when a new disease appears is, “Where did this come from?”

Many viruses jump from animals to humans, a phenomenon known as “zoonotic spillover.” Although it remains unclear which animal was the source of the current coronavirus pandemic, all the attention is on bats.

The transmission of viruses from bats to humans is not just a matter of a bat biting someone or licking their blood. (Bats do not suck blood as they do in vampire stories.) It is often a much more complex scenario that may involve an intermediary host.

Many other animals are also known to be repositories for human diseases. Rodents carry the plague, pigs transmit influenza and birds transport the West Nile virus. So, why are bats so often blamed for transmitting disease?

As a scientist who has spent years studying the evolution of bats in several countries in South America, North America and the Caribbean, I think that these night creatures are often the victims of misinformation. Most people are afraid of bats, and there is a tendency to connect them to bad things.

Heating up

One reason bats are blamed for disease has nothing to do with science. Bats are associated with vampires and horror stories, which causes fear and misunderstanding towards these flying creatures.

The other reasons are grounded in evidence. Bats are the second-most species-rich order of mammals. There are more than 1,400 species distributed worldwide, except in Antarctica. They live in urban and natural areas, and they all have the potential to carry viruses. Bats are also mammals, and this relatedness to humans makes them more likely to be hosts of zoonoses than birds and reptiles, for example.

Read more:
Viruses can cause global pandemics, but where did the first virus come from?

Some bat species prefer to live in colonies, close to one another, creating a perfect setting for pathogens to spread between each other — and to other species who might also share the space. Bats are also the only mammals capable of true flight, making it easier for them to spread diseases through their guano (bat feces).

But what is particularly interesting is their tolerance to viruses, which exceeds that of other mammals. When bats fly, they release a great amount of energy, which increases their body temperature to 38–41 C. The pathogens that have evolved in bats are able to withstand these high temperatures. This poses a problem for humans because our immune system has evolved to use high temperatures — in the form of fevers — as a way to disable pathogens.

Seed dispersers

Despite all the negative press bats receive, they make positive contributions to the environment and to our lives.

The majority of species feed on insects, helping protect crops from infestations. They are involved in seed dispersal, such as those from fig trees and silver palms, and the pollination of many plants, including several commercial ones, such as the eucalyptus and agave, which provide natural fibres and beverages, such as tequila and mescal.

Read more:
No, Aussie bats won’t give you COVID-19. We rely on them more than you think

Bats have also been used in scientific research to understand adaptive evolution (how beneficial mutations become common in a population) and how ecosystems function. They have also be used in studies on aging, cancer, immunity and biomimetic engineering.

And most importantly, bats might actually help to provide the solution for COVID-19 and other viruses. Bats do not get sick from many viruses that might kill humans, and research on how bats achieve this could hold the key to help us fight this and future outbreaks.

‘Bad reputation?’

It is clear that researchers around the world are doing whatever they can to report the origin of SARS-CoV-2. So far, the most accepted hypothesis is that the novel coronavirus originated in bats. The genome of the virus found in humans is 96 per cent identical to one found in bats. But are these findings being reported the way they should?

Not always, from the bat’s perspective, at least.

Complex scientific studies are being published very fast, which is understandable considering the urgency of this new disease. However, this hastiness is leading to mistrust, confusion and sometimes even fear and hatred towards these flying mammals.

In some places, this growing “bad reputation” has led to the intentional and needless killing of bats in the name of protecting public health. But this could have negative consequences: disturbing hibernating bats causes abnormal arousal and stress, which could lead to the spread of new diseases.

But even if bats are proven to be the source of this virus, they are not to blame for the transfer of SARS-CoV-2 — humans are. We destroy natural habitats at a frenetic speed; we kill threatened species, changing entire food chains; we pollute the air, the water and the soil.

It is expected that new pathogens that were previously locked away in nature will come in contact with people and spread fast as people move around the world. The people who blame bats for COVID-19 should look in the mirror to see if the real vampire resides within.The Conversation

Livia O. Loureiro, Research Fellow, The Cente for Applied Genomics — Sickkids Hospital, University of Toronto

This article is republished from The Conversation under a Creative Commons license. Read the original article.


Why do chipmunks live on the ground but squirrels live in trees?

Chipmunks have a superpower: hibernation.

Andrea Wishart, University of Saskatchewan

Curious Kids is a series for children of all ages. Have a question you’d like an expert to answer? Send it to CuriousKidsCanada@theconversation.com.

Why do chipmunks live on the ground but squirrels live in trees? — Audrey, 7, Kingston, Ont.

Animals show us that there are many places to make a home. What drives one to nestle in an underground burrow and another to nest in the branches of a tree has a lot to do with two things: family history and how its body works.

Scientists called “evolutionary ecologists” study how living things relate to each other and their environments (ecology) and how these relationships might have influenced what living things look like and how they behave over time (evolution).

The first question to ask is whether or not these chipmunks and squirrels are closely related.

All in the family

Chipmunks and squirrels, which are actually “tree squirrels,” are members of the same family called Sciuridae (sigh-YUR-i-dee), which includes:

Chipmunks and squirrels are like distant cousins whose most recent common ancestor lived a very long time ago — over 20 million years ago. Distant cousins indeed!

Adaptations help animals be successful

Members of the squirrel family live around the world on every continent except Australia and Antarctica. Different behaviours, shapes and body functions can help increase the chance that they will survive and reproduce in their different habitats. These are called adaptations.

A grey squirrel and its nest in a tree in winter.

One adaptation that helps animals avoid extreme cold temperatures or low food is hibernation. Underground burrows may have helped the ancestors of chipmunks survive better in their environment.

When chipmunks hibernate, they find a safe place underground to curl up. Then they slow down their heart rate and lower their body temperature by so much that they don’t need to eat.

The ancestors of tree squirrels probably hibernated too, but at some point they lost this superpower. Tree squirrels avoid harsh winters by hanging out in their nests, and digging up the seeds and nuts they buried in the fall to eat.

This fossil squirrel Protosciurus jeffersoni was discovered in Wyoming in 1975. Scientists believe it lived about 37 million to 32 million years ago.
(Ryan Somma/flickr), CC BY-SA

The oldest known member of Sciuridae (Douglassciurus jeffersoni) looked very similar to what we know today as tree squirrels, with long fingers and toes to help grip branches, and a long bushy tail to help with balance.

Become a squirrel scientist!

With school closed due to the coronavirus, you may be spending a lot more time at home than usual. This is a great opportunity to get to know your local squirrels!

Chipmunks and tree squirrels like to eat seeds (like sunflower seeds), nuts (like walnuts and acorns), and peanuts. Put small dishes of two or more of these snacks in a place where you can watch through a window.

  • How many seeds does the animal take in 10 minutes?
  • Do they eat the food or do they take food away to store?
  • After they visit do they go into burrows or up into a tree?
Keep track of your observations in a notebook using words, pictures, charts or graphs.

Bring the food inside at night so you don’t attract other wildlife like skunks or raccoons. Never feed wildlife from your hands, for your safety and the safety of the animal.

You can help scientists see where different animals live! Take photos of your backyard visitors and ask a grown-up to upload them to iNaturalist. If you aren’t sure what species you have, that’s OK! Other experts can help identify your animal from the picture.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsCanada@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit — adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.The Conversation

Andrea Wishart, PhD Student in Animal Behaviour, Ecology, and Evolution, University of Saskatchewan

This article is republished from The Conversation under a Creative Commons license. Read the original article.