Nature Nearby: Bats: friend or foe? The jury is still out
By Fred Seitz
Bats are amazing animals. They are the only flying mammals (flying squirrels are only gliders). While flying squirrels are usually depicted as cute and familiar, courtesy of cartoons like the famous Rocky and Bullwinkle, bats get the short end of the stick. They are mostly seen in late-night horror flicks with Bela Lugosi-like vampires walking around. But out of more than 1,200 species of bats, only three feed on blood, and then typically that of sleeping cows, not people. And these vampire bats all live in Central and South America, not your attic.
Bats also live in caves and empty broken-down houses, which are prominent in some of those late-night horror flicks, as well. Interestingly, caves were historically mined for bat guano, which was used to make gunpowder and fertilizer. Illegal mining and marketing of bat guano for fertilizer production still occurs.
I should note that I am a former caver and bat enthusiast. Once during an adventure in a bat field, I saw an extraordinary sight: The walls were lined with hundreds of female bats, nursing their young. Mom Bat hunts for insects at night, but she returns to nurse her young ‘un at daybreak because of the little one’s shriek, which she recognizes among the chorus of hundreds of hungry baby bats. So bats are great moms, along with being neat fliers and pest controllers.
Caving is more restricted now because a group of cavers in New York were found to have inadvertently transferred the fungus that causes white-nose syndrome (WNS) to bats as they caved. WNS causes the bats to wake too early from their hibernation. Their activity during winter’s chill causes them to burn off the fat they stored during the spring and summer, depriving them of the energy reserves they need to survive the rest of the winter. This is particularly devastating to females, who are typically pregnant with their young during the winter, and frequently results in the death of both the mother and her baby. WNS has spread across the continental U.S. and most Canadian provinces, pushing many of our bats to near extinction.
Despite my pro-bat bias, I acknowledge that bats carry some diseases, including Marburg, rabies and types of coronavirus, that are highly unfriendly to humans.
Part of the reason that bats carry such delightful viruses without getting sick from them is that they have a high metabolic rate, which is necessary to support wing flapping. Research suggests that bats’ high metabolism may enhance their ability to produce interferon, which likely helps them survive and resist the sickness and mortality from those viruses they carry. And while we still have a lot to learn about disease resistance and transmission, we do know that some animals with relatively low metabolic rates, including humans, do not fare as well against these viruses.
The Centers for Disease Prevention and Control (CDC) has determined that the coronavirus causing the pandemic is related to the SARS virus and very likely came from bats that were sold in wet markets in China. These markets often carry live bats and other animals, so their saliva and other deposits may be also in the marketplace, and that presence promotes human exposure.
The Fish and Wildlife Service has recommended that scientists studying North American bats suspend their research, as a researcher carrying the coronavirus could inadvertently transfer it to these bats, potentially compromising their health and risking further spread among humans.
Our local bats (and the majority of bats worldwide) are insectivores, and they provide a great, no-cost service to home gardeners and the agricultural industry, alike. A single bat can eat from 6 to 8 thousand insects during a single night, saving us tremendous financial expenditures for pesticides, as well as risks from those toxic chemicals in our food. And all those mosquitoes that bats eat? Thousands that won’t be eating you.
I have had the “privilege” of being bitten by some of our local bats during some field training in years past, but pre- and post-exposure rabies shots have spared me from foaming at the mouth (though my wife, my friends and some of my former coworkers from the CDC have always maintained that I’m a bit batty).
If you should encounter a bat in your house or shed this spring, just open up your doors and windows and let it find its way out. And consider asking them to munch on some mosquitoes or caterpillars as they go.