Agave is one of the great resources of arid North America. It was a staple food for Native Americans. It's notable for its beauty – its luminous floret and towering stalk. Agave spirits – tequila, mezcal – are prized exports.

But as close as the relationship between agave and humans has been, one mammal in our region has an even more intimate relationship with the plant.

Each summer, Big Bend National Park is home to a population of endangered Mexican long-nosed bats. As the glow fades on the Chisos' ramparts, the bats set out from a mountain cave. They're hungry, for only one thing: agave flower nectar.

The relationship benefits both bat and plant. Human activity imperils tha...