"They're location calls," Bennett explains of the variations. "You know, navigating: what to avoid, what to seek. One is looking for identifying the landscape, the other is identifying prey. And another is social calling -- talking to each other."
And how do we humans know how to distinguish among the calls?
"It's the pattern that we see when we're looking at the sonogram," Bennett says. "You can also hear it, to some degree. Sometimes when the calls start off in a discreet, steady pattern, that might be like a search phase. It's examining its environment, it's understanding what is where. Then when it gets into a feeding stage, the calls get much more choppy -- and frequent. You know. And then it's just, chopchopchopchopchopchopchop, and then it's quiet. And then it starts again."
It begins to rain -- at first a light drizzle, then a less-light one. The sonar detectors are not waterproof. They are, however, expensive -- $1,000 a pop. We put them away. We return to the second net. It has has something snagged in it. It's smaller than the bird was. It seems to be darker. It seems to be a bat.
"Are you excited, Rodrigo?" Menchaca asks. "No!" he replies, grinning, as he bounds down the bank toward the net.
It is, indeed, a bat -- a big brown, as Medellín predicted. Which is a slightly ironic name: With its wings collapsed, the creature fits neatly into the palm of Medellín's hand. He holds it with his thumb pressed onto its back, in the soft spot where its wings would spread if they weren't encumbered by a human appendage. None of this hurts the bat, Medellín assures us. He picks up a white pouch with a drawstring opening. Into it, carefully, he places the bat.
Medellín demonstrates the wingspan of a bat. (Megan Garber)
"This is just poplin, which is 100-percent cotton," he says, "and it's very non-abrasive for the wrists of the bats." He tends to talk about bats that way, in human terms. He discusses bats' shoulders and joints. Wings like fingers and arms. He ties a rope around his waist. He ties the strings of the pouch to the rope -- a bat belt for the Batman. We continue walking. We're walking quickly. We've caught one bat; there's a chance we'll catch more.
We do, in the end, catch more -- a silver-haired that squeals and hisses under Medellín's thumb. And then another big brown. Medellín will add them to his bat belt. We'll follow a park guide to a clearing near 110th Street, where Pearl, the dean of Macaulay and a friend of Medellín's, has assembled a group of students. They're eager to see a bat.Smartphones and winged mammals (Megan Garber)
The students, clad, like Medellín, in BioBlitz t-shirts and tags, crowd around the professor as he stands, thumb on shoulder, demonstrating his catch. Phone-cameras flash. Medellín stretches out the animal's wing -- assuring the students, again, that this won't hurt the bat. He points out the fine bones, the fine veins, the fine hairs that help the bat navigate its way through the air. He is delicate. When he captures a bat like this, Medellín notes, his policy is to try to make it not only painless for the bat, but also worth the animal's while: He feeds the animal before setting it free. "To help it with its energy reserves," he says. A hungry -- or angry -- bat (Megan Garber)
This bat, made into a sudden celebrity, has earned its reward. Medellín perches on a block of cement, carefully cupping the pouches as he sits. The students reorient themselves around him. From one of his bags, he removes a plastic container that looks like it would contain yogurt save for the fact that "MEALWORMS" is written on its top. Medellín lifts the carton's lid. He cradles the bat, on its back, using the cotton pouch as a kind of makeshift bed. The animal's mouth is open, revealing tiny teeth. Using a pair of short tweezers, Medellín extracts an inch-long worm from the container. He coaxes the worm into the bat's mouth. Both animals squirm.
But the students are transfixed.