Editor's note: This story was jointly produced by PRI's The World and NOVA.

Bats often get a bad rap, but they are important to natural ecosystems — and to humans.

A biologist in Mexico is trying to convince his countrymen to protect bats, and he is training a new generation of researchers to look after the animals.

It's not uncommon for Rodrigo Medellin to start his day at night.

At the moment, he has a headlamp switched on and is walking into the Cueva del Diablo — the Devil’s Cave — near Tepoztlán, Mexico.

Suddenly, Medellin stops. The ceiling of the cave, just eight feet above his head, is furry and moving.

“There’s a lot of Mexican long-nosed bats over here,” he said.

About 2,000 Mexican long-nosed bats are making soft, high-pitched noises. But looking up at a colony like this is just asking for trouble.

Medellin grimaces.

"I’m getting pee on my eyes,” he proclaimed.

He turns away to clear his eyes. But, before long, he looks up again and points.

“They’re mating,” he said. “Just look at pairs forming. A male is grabbing a female from behind.”

Medellin is a biologist at the National Autonomous University of Mexico, and he has been coming to this cave for three decades. It was just a few years ago that he and his students first saw Mexican long-nosed bats mating here, or anywhere.

“From then on, we’ve been trying to find other caves where this endangered species mates,” he said. “And we haven’t found any.”

That makes this cave incredibly important. He figures there are about 4,000 of these bats here in all. That is down from maybe 8,000 a decade ago. He fears that people are disturbing the bats.

Medellin shakes his head as he notices fresh footprints in the cave, probably from locals.

“They’re not supposed to come in for anything at this point in the year, which is when the bats are mating,” he said.

A Lifelong Love of Animals

While many types of bats are doing just fine in Mexico, Medellin says humans threaten the survival of certain species. People often unintentionally destroy bat roosts and habitat, and in some places villagers intentionally kill bats.

Medellin has made it his mission to help these animals, by studying them and fighting for their protection.

Back in his lab in Mexico City, Medellin says his passion for bats, indeed, for all animals, started early in life.

“My first word was not mama or dada — it was flamingo,” he said.

He read about flamingos and other animals nonstop as a kid. When he was 11, he appeared on a popular national TV quiz show. He was able to choose which subject he would be quizzed on, and he selected mammals.

“I did not win,” Medellin said, “but in the process of spending six or seven weekends on TV, a lot of people saw me — including the people at the University of Mexico that, at the time, were the experts on bats.”

Those scientists invited him to help in the lab and the field.

Medellin was amazed that bats came in such a wide variety of shapes and sizes — “long snouts, short snouts, small eyes, big eyes, huge ears, rounded ears, pointed ears, colorful as can be,” he said.

Medellin was hooked. He says everyone should appreciate bats and be grateful to them.

Bats play an important ecological role. They eat massive amounts of insects, disperse seeds and pollinate plants.

But convincing the public that bats are worth protecting is not always easy. Medellin says he has to persuade people that doing so is in their own best interest.

Engaging Locals to Save Bats

In Mexico, Medellin has hit on something he thinks could be a winning argument.

“Our own Mexican identity’s very closely linked to tequila,” he said.

Tequila is made from the agave plant.

“We would not have tequila if it wasn’t because of the bats pollinating agaves for millions and millions of years,” he said.

He argues that if Mexicans want tequila in the future, the country has to protect its bats.

Medellin has started a program to offer a special consumer label to tequila producers who farm their agave plants in a bat-friendly way.

Medellin is also working to save bats in more than a dozen other countries. He says in each place he has to modify his pitch so that it resonates with the local residents.

“If you want to do effective conservation, the leaders have to be the locals because they know the context, the culture, everything,” he said.

Fledging New Researchers

Medellin, 55, says to save bats in the long run, there has to be a younger generation of conservationists ready to take on this fight. So he has been training a small army of researchers. He rarely enters a cave alone.

Back at the Cueva del Diablo, Medellin is accompanied by Rubén Galicia, who is working on his master’s degree. He says he loves being around bats.

“I enter a cave and shut off my light,” he said. “Then it’s silent, except for the sound of the bats.”

Today, Medellin’s students have set up a net in front of the entrance to the cave. It's not long before they catch a bat. Medellin untangles it from the net.

He hands the bat, a female, to a student who weighs and measures it.

Medellin and his team want to know when the bats are reproductively active so they can determine the best time periods to restrict visitor access to the cave.

Medellin takes the animal back. He holds it in his hands and prepares to release it.

“We’re going to recharge its batteries, giving it a little bit of guava juice there,” he said.

The bat laps it up.

Medellin holds out his hands.

“Okay,” he said. “One, two…”

The bat waits for a moment.

“And three.”

The bat flies off, back into the night.