'Bat Man of Mexico' Follows Migration of Tequila Bats

Rodrigo Medellin coats bats in harmless UV dust to track their travels.

Ecologist Rodrigo Medellin with a lesser long-nosed bat
Ecologist Rodrigo Medellin with a lesser long-nosed bat.

Amy Cooper

Ecologist Rodrigo Medellin has been fascinated with bats since he was young, even keeping them in his bathroom when he was growing up.

These days, Medellin has been tracking the migration of the lesser long-nosed bat across Mexico. The species is critical to the production of tequila because they pollinate the plants the drink is made from.

Right now there are seven brands of tequila and three brands of mezcal that are recognized as bat-friendly, Medellin says. That means the manufacturers allow at least 5% of their agave plants to flower, so bats can visit and feed from those flowers.

To help with their conservation, Medellin learns all he can about their migration.

When Medellin follows the bats, he does it armed with a glowing ultraviolet powder. He coats the bats with the harmless dust, which they lick off and digest. By following glowing bat droppings, Medellin can trace how far the bats have flown.

Medellin’s travels with the lesser-known bats are the subject of the new “Nature: The Bat Man of Mexico” documentary. Premiering today (June 30) on PBS, the show is narrated by David Attenborough.

In an email interview, Medellin talked to Treehugger about bat conservation, UV dust, and why everyone who has been in the field with him falls in love with bats.

Treehugger: Where did your fascination with bats start?

Rodrigo Medellin: I was 12 or 13 years old when my first bat came into my hands. At the time I had been already helping at the mammal department of UNAM [National Autonomous University of Mexico] and people kept telling me how amazing bats were and I realized how unfairly treated they were. 

So of course when I got my first bat in my hand (I distinctly remember, a Waterhouse leaf-nosed bat, Macrotus waterhousii) I was trembling with emotion at how incredibly amazing its ears were, its noseleaf, its little claws, its astonishing soft, pliable wings were, and its silky, beautiful fur was.

The combination of mystery (hardly anyone knew anything about bats back then), fascination (sooo many interesting features to it), and unfair treatment they represented made me decide right there and then, in the middle of the Cañon del Zopilote in the state of Guerrero, to just continue learning and defending bats for the rest of my life.

What was your trek like, following the lesser long-nosed bat?

My journey following the lesser long-nosed bats´ migration has been fun, surprising, amusing, educational, and rewarding. Starting with getting to know them in southern Mexico in a cave, and then beginning to uncover their migration, their biology, and their conservation needs, I started by mapping the caves and other roosts known at the time. 

Then the Smithsonian and Fish and Wildlife Service´s invitation to join the team to assess their status, through Don Wilson, at the time curator of mammals at the Smithsonian, and a mentor and friend throughout and to this day, put me front and center to really dig into the bats´ conservation needs and biological mysteries.

We succeeded in listing them in the U.S. Endangered Species Act, and the Mexican equivalent, NOM-059. Right after that happened, I began working with my team to educate the tequila industry about the need to protect these bats, and we assembled a recovery plan.

We produced educational materials, developed management plans for caves, worked with the Mexican government to protect their caves in protected areas, all this while scouting and scouring the country north, south, east, west to identify and map the most important roosts. Then we devised the technology to census and monitor these roosts... another challenge.

Then after most of the priority caves had been surveyed and their future secured by educating the local people, their populations began stabilizing or growing. The moment of removal from the Mexican Federal List of Endangered Species was a most rewarding and happy moment of my life. We threw a party (lots of tequila, of course), and the media took this good news and propagated the wave of success and happiness. My team was sooooo happy! 

And then only a couple of years later we launched the Bat Friendly Tequila and Mezcal Program. This program continues to grow and the bats continue to recover! What is not to enjoy, to like, to celebrate! A dream come true! Nothing less!

Ecologist Rodrigo Medellin holding a lesser long-nosed bat
Medellin gets up-close with a lesser long-nosed bat. Amy Cooper

Why is this species so important?

This bat embodies everything good about bats: They are so incredibly personable, nice, decent, polite, and of course crucial, that every person who has been with me in the field catching them gets convinced about loving bats for the rest of their lives. They rarely attempt to bite, they often come into the nets completely covered in pollen, with big, bright eyes, trying to get away but still not trying to harm you in any way.

And this character is behind the amazing landscapes of the Sonoran deserts and more because they pollinate columnar cacti? And on top they also pollinate agaves from which tequila and mezcal come? What did we human beings ever do to deserve such an amazing species living here in Mexico?

How do you use the UV dust coating to follow a bat’s journey?

We first sprinkled the bats that were emerging from the cave with yellow-glowing ultraviolet fluorescent powder by standing on top of the mouth of the cave and shaking kitchen colanders on the emerging bats. Then I had two other teams, one 40 km north of the cave and another 50 km northeast of the cave, waiting for the bats to visit cactus flowers. 

My students had instructions to shine a fluorescent powder lamp on the bats while they were still in the nets to check for yellow glowing powder. That would demonstrate that they were coming from the cave. 

Then they would put the body of the bats in a Ziploc bag, leaving the head out to avoid interfering with their senses, and smear them with orange glowing fluorescent powder (at 40 km) and blue-glowing (at 50) powder. 

The next night I entered the cave with a UV light to look for blue-glowing and orange-glowing bat feces. And we found that too! Confirmed!

Why is it key to learn their migration patterns?

Thanks to using the UV powder, we now know that these bats can fly 100 km or more in one night along their migratory route. That simplifies our ongoing search for the stepping-stone caves that they use along their migratory route, and that also helped us understand their loyalty to the cave where they have their babies. These bats came back again and again!

What have you learned and what are the next steps?

We now know about the incredible flight power these bats have. We know a lot more about their migratory movements, and we also know a lot about how they use the landscape and their flowering plants. 

Next year we will attach tiny miniature GPS trackers that will help us solve the biggest question of all: We will be able to follow their entire migratory route in detail! The height over the ground that they fly, whether they use stream beds, canyons, mountain sides, or mountain crests to migrate, whether they fly solo or in groups, whether they migrate night after night consistently or they take breaks along the way, why and where. 

Why do males not migrate? Why do only about half of the females migrate? Can a female that was born in the migratory segment of the population switch to non-migratory and vice versa? And how is it that they are able to conduct those great, long-distance flights, powered only with sugar water?

So many questions!

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