Leaping Leeches! Watch These Bloodsuckers Jump.

Land-dwelling leeches can seem like placid creatures. But when they’re on the hunt for blood, look out.

An appetite for blood may have provoked acts of startling athleticism, documented in a pair of videos released Thursday by two scientists alongside a study in the journal Biotropica. In each, a brown pillar of flesh and muscle, standing atop a green leaf, waves back and forth on its quest for blood. Then, it coils itself into a comma, bunching up its lower half. Finally, the leech leaps, flying through the air with a kind of wild abandon.

Lean closer, cup your ear: You can almost imagine you hear a tiny “Yahooooooo!”

Mai Fahmy, currently a postdoctoral researcher at Fordham University and a visiting scientist at the American Museum of Natural History, took the first video in Madagascar in 2017. At the time, she had never heard of the long-running debate among scientists about whether leeches could jump.

“It takes a few years of leech study before you learn about the great debate,” reflected Michael Tessler, a specialist in leech biology at Medgar Evers College of the City University of New York and a research associate at the natural history museum. He is Dr. Fahmy’s co-author.

Her 10 second clip, taken on a whim, turned out to be the first recorded visual evidence known to science of leeches jumping.

There had been other claims of leaping leeches. In 1881, the biologist Ernst Haeckel visited Sri Lanka and described the behavior: Not only did they crawl on the ground, he wrote, but they could also “spring to reach their victim.”