It’s not hard to find bats for sale in the marketplaces of Bolivia. They’re usually tucked away in pungent shoeboxes, some with as many as 20 bats jammed together, the live ones crawling over those that have already succumbed to disease or stress.

People buy them so they can drink fresh bat blood for its purported healing properties—particularly, they think, to help manage epilepsy. “The belief is well-rooted within our society, mainly in the Andes,” explains bat specialist Luis F. Aguirre, director of the center for biodiversity and genetics at the University of San Simon, in Cochabamba. “I receive calls requesting bats at least five times a year,” he says.

Aguirre is not in the business of selling bats to the highest bidder. For the past 20 years he’s worked to safeguard the animals as head of the Bolivian Bat Conservation Program, a network of volunteers and professionals who conduct research and educate people about bat misconceptions. But because Aguirre is a bat man, and because people want live bats—they contact him hoping he’ll be able to help procure fresh stock.

“I once received a call from France from a Bolivian asking about bats,” he says. The caller wanted to treat a child’s epilepsy by feeding him bat blood. In that instance, and every other like it, Aguirre repeats the same refrain: That there’s no proof of any medicinal benefit from drinking bat blood and he strongly opposes the practice.

Yet the belief—and killings—persist. Officially, bat hunting is illegal. Bolivian law forbids the killing or sale of any wild animal without proper permitting, and the offense is punishable with up to six years in prison. Still, research Aguirre and colleagues published in 2010 reported that more than 3,000 bats were sold every month in just four major Bolivian cities. The species were varied but included fruit bats, insect-eating bats, and vampire bats.

Aguirre says regular monitoring suggests that sales remain at similar levels today—and may even have increased—despite greater attention on wildlife crime and public pressure to address it. The only real difference is that the bats are no longer displayed as openly as in years past, he said in an email. “But it’s not difficult to find them.”

Whereas hunting bats is illegal, the right to practice traditional medicine is nevertheless backed with the force of law. When longstanding cultural practices and wildlife protection are somewhat at odds, the latter often takes second place, says University of Mississippi anthropologist Kate McGurn Centellas, who studies traditional medicine in the country.

To date, there has been no record of arrests related to bat killing or trading, according to Rodrigo Herrera, legal assessor at the General Directorate of Biodiversity and Protected Areas in the Ministry of Environment and Water. The Bolivian government says they have no official records of bat killings and that their only related report is of an incident from 2015 in the capital, La Paz, where 22 bats of various species were being sold for medicinal use and were confiscated. All the animals later died.

THE “POWER” OF BAT BLOOD

The belief that the blood of a bat will help heal someone with epilepsy is hard to prove or disprove. According to Aguirre, if a person with epilepsy drank bat blood, suffered no seizures for a time, but then had one, believers might simply say that the blood’s potency must have faded—signaling the need for a fresh bat.

The practice is steeped in ritual, and the origins of the putative powers of bat blood remain obscure. Bolivians’ have a deep cultural commitment to traditional medicine, which can include animal offerings and herbal remedies. To bring good luck to a home or scientific laboratory, for example, a dried llama fetus may be burned and its ashes buried under the building, Centellas says. She notes that blood is also seen as a strong life force that, if consumed, can transfer some of its properties.

As for bats, their value likely comes from the fact that they’re viewed as a powerful creature with unique characteristics, Centellas says. “They fly, but they’re mammals—not birds. They’re seen as not neatly fitting into any category, so that might be the source of their purported curative powers.” In particular, she adds, “by consuming bat blood, you can perhaps balance or correct what would be seen as a disturbance or imbalance in the human body—manifested as seizures, or what we know in the biomedical system as epilepsy.”

Typically, a bat would be obtained alive, its head chopped off, and the blood drunk fresh, Aguirre says. But a second option, if the bat is already dead, would be to fry the bat with its fur on and place it in a cloth bag that would then be soaked in alcohol for future quaffing—something akin to mezcal served with a worm inside the bottle.

Centellas, who has not witnessed either ritual, says the two practices seem consistent with the general logic and approach of others in Bolivia that she has seen for herself. Snakes, for example, are often placed in alcohol and drunk later, she says, in the hope that the concoction will increase virility, stamina or fertility, among other things.

THE BIGGEST BAT KILLERS

Bats sold for their blood—which Aguirre’s market surveys show may include various species of fruit bats, insect-eating bats such as the mouse-eared bat, and vampire bats—are not rare enough to be considered endangered. (Read about vampire bats here.)

View Images Up to 20 bats of various species, including vampire bats like this one, may be crammed together in shoeboxes for sale in Bolivian markets. Photograph by Joel Sartore, National Geographic Photo Ark

People who sell bats in the markets also aren’t the ones who hunt them. Intermediaries in places where the bats roost may come upon them in abandoned houses, caves, and forest areas, Aguirre says. They often snag the bats in nets like those used to catch butterflies. They’re then put in cloth bags or boxes for transport to the urban markets.

Dire as this sounds for Bolivia’s bats, killing them for their blood is far from their gravest threat, says Rodrigo A. Medellín, co-chair of the bat specialist group at the International Union for the Conservation of Nature, which tracks the status of species.

“The biggest threat continues to be roost destruction and disturbance, and habitat destruction,” Medellín, who is also a National Geographic explorer, emphasized in an email. “Three thousand bats a month is unfortunately nothing compared to the mortality caused by habitat change and roost destruction.”

Any reduction in the number of bats can be harmful to ecosystems by, for example, taking out crucial plant pollinators and bug exterminators. And opportunistic hunting for bats puts people at risk too.

“Insect-eating bats are very good at vector control—they eat mosquitoes and other arthropods that carry diseases or parasites like malaria that infect people,” says Jonathan Towner, a disease ecologist at the U.S. Centers for Disease Control and Prevention, in Atlanta, Georgia, who specializes in highly dangerous pathogens. With fewer bats, there will be more of those bugs, he notes, and that may boost the chances that people will be exposed to diseases such as yellow fever, zika, or malaria.

Spending time wrangling bats also carries direct health risks. The chief concern is rabies, according to Brian Bird, a virologist, veterinarian, and bat expert at the University of California Davis One Health Institute. And an infected bat in a stressful situation, such as being crammed in a box with other bats, may bite more than usual, spreading rabies.

Vampire bats, which are found only in Latin America, “are in many ways the perfect vector for rabies,” says Gerald Carter, a National Geographic explorer and vampire bat expert at Ohio State University, in Columbus. They drink blood, and rabies is transmitted by biting—allowing the virus to jump from an infected bat to the animal it bites.

For people drinking bat blood, the risk of getting rabies is low because the virus is most prevalent in saliva and tissue like the brain, not other bodily fluids. Still, there may be other pathogens—perhaps new ones—that could be present in raw bat blood, Towner says. And if the bat died on its own, he adds, that itself should be worrying—a dead bat or a sick bat is much more likely to have disease.

No official records have linked the practice of drinking bat blood to sick Bolivian patients. But that could just be a matter of lackluster surveillance, Bird and other public health experts say. “When you kill and drink the blood of these animals, you’re exposing yourself to a whole spectrum of known and potential pathogens,” he warns.

Bats, in particular, have a recent history of being linked to emerging viruses with serious consequences for people—like Ebola, SARS, and a cousin of Ebola’s called Marburg. In each instance, a pathogen jumped from its natural reservoir (another species), to a group of people who had little prior exposure to it and consequently very little immunological protection against it—allowing a flare-up to become a major crisis.

“It really is these rare spillover events that cause epidemics,” Bird says. “While we know spillovers are rare, it’s people engaging in high-risk activities like consumption of bush meat where an uncommon spillover event becomes more common.”