Photo: USFWS

Is there anything so perfect on a hot summer afternoon as the cold sting of a strong margarita—the salt, the slush, the citrusy tang of tequila and blended sunshine?

Well, the next time you sip such a concoction—or anything else made with tequila—take a minute to think about bats.

Tequila comes from blue agave, and the lesser long-nosed bat, which is considered endangered in both the United States and Mexico, is the plant’s primary pollinator. Like hummingbirds, the bats hover from flower to flower lapping up the agave’s sugary goodness, all while showering it in pollen from other agaves they’ve visited that night.

Bats get an energy-rich meal to fuel their flights and feed their babies. Agaves get the pollen they need to create new agaves. And we get tequila sunrises and body shots. Sounds like a match made in heaven, right?

Yeah, no.

Although tequila is more popular than ever in the States, almost none of our agave plantations provide food for lesser-long nosed bats, says Rodrigo Medellín, a bat expert at the University of Mexico.

To understand why, you have to know a little bit about agave sex—or really, the lack of it.

Depending on the species, most agaves can live between eight to fourteen years (though some live quite a while longer). Over the course of that life span, the plants flower exactly once, and there’s no missing it. Each agave erects a towering stalk into the sky, often several times the plant’s own height, looking like something out of Dr. Seuss.

To produce this flowery bat beacon, the agave spends its entire life gathering sugar. It burns up this stored energy in a final growth spurt, a last-ditch effort to attract pollinators and pass on its genes. Once the show’s over, the agave dies.

The plant’s sweet savings is what the tequila industry is after. Producers harvest their agave just before the plants flower, ensuring sugar levels are at their peak.

Photo: jay8085 Blue agave growing in Tequila, Mexico

“So you have hundreds of thousands of hectares in western Mexico that are planted with potentially good food plants for the bats, but they never come into bloom,” explains Medellin.

When agaves are harvested in this way, they can still reproduce, but only through clones. The mother plant sprouts clones at its base, and the plant lives on. The problem, he says, is that these genetic replicas miss out on the benefits that come with sexual reproduction.

For more than 20 years, Medellin says he’s been trying to warn the Mexican Tequila Regulatory Council about how this practice was hurting agave farming in the long run. “I’ve been telling them that the process of replanting and replanting and replanting was a dead end,” he says. “They were losing all genetic diversity and with it all resistance to any disease that would come along.”

Medellin’s predictions came true in the late 1990s. A combination fungal and bacterial disease nicknamed TMA (Tristeza y Muerte de Agave, or “the wilting and death of agave”) struck the tequila industry hard. It affected around a quarter of blue agaves in the field and cost producers about $200 million in 1999. Today, Medellin says, TMA infects up to 40 percent of agave plants.

The next time you're sipping on a margarita, take a minute to think about bats.

To solve this problem, he has teamed up with a guy named David Suro-Piñera, president of the Tequila Interchange Project. His goal is to help the bats and the agaves from inside the industry—in other words, to convince producers that it’s in their best interest to let a few of their plants die in exchange for a “bat-friendly” label.

“What Rodrigo is proposing is exactly what we want,” says Suro-Piñera, who also owns a tequila-focused restaurant in Philadelphia. “To allow these plants to reproduce by cross-pollination so that we get stronger plants that are capable of defending themselves.” In addition to getting the industry to change its ways, they hope to recruit the help of American bartenders, since the Sams and Woodys of the world are the gateway to consumers.

So, where can you get this bat-friendly tequila? Well, don’t look for it from the likes of Jose Cuervo and Patrón. Instead seek out small-batch producers like Siete Leguas, Tequila Tapatio, and Tequila Cascahuín. Still, those companies’ bat-friendly stickers—which are more about awareness than certification—probably won’t hit the shelves for another year, after Medellin and company check out their operations.

In the meantime, there is one way to change your drinking habits that may help the bats and the agave. Start drinking mezcal.

If you’re like me, the thought of mezcal conjures up images of soggy worms and bloody elbows. (Don’t ask.) But unlike tequila and almost every other commercialized spirit on earth, mezcal comes from the wild.

“Think about beer, vodka, rum, wine, whiskey, you name it,” says Medellin. “They come from humongous monocultures that are really bad for the earth.” Mezcal, on the other hand, is harvested from any of the other dozen or so varieties of agave in Mexico, typically in forests rather than fields. The harvesters also leave far more plants behind than they take. Medellin calls the mezcal industry both sustainable and “naturally set up to be bat-friendly.”

In fact, tequila is just a kind of mezcal, which technically refers to any type of “oven-cooked agave.” And a lot of people think mezcal is the superior spirit. Put that in your margarita and slurp it.

Photo: Quinn Dombrowski

onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.