Ground-dwelling leeches may seem like peaceful creatures. But when they’re out for blood, watch out.
An appetite for blood may have provoked startling athletic feats, documented in a pair of videos released Thursday by two scientists along with a study in the journal Biotropica. In each, a fleshy brown pole, standing on a green leaf, sways back and forth in its quest for blood. It is then rolled into a comma, gathering its lower half. Finally, the leech jumps, flying through the air with a kind of wild abandon.
Lean closer, fill your ear: You can almost imagine hearing a “Yahoooooo!”
Mai Fahmy, currently a postdoctoral researcher at Fordham University and a visiting scientist at the American Museum of Natural History, made 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 several years of studying leeches before you learn about the big debate,” reflected Michael Tessler, a specialist in leech biology at the Medgar Evers College of the City University of New York and a research associate at the natural history museum. He is the co-author of Dr. Fahmy.
Her 10-second clip, taken on a whim, turned out to be the first recorded visual evidence known to science of leech dancing.
There were other claims about leech dancing. 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 “spawn to reach their victim.”
Scientists have long been skeptical of such anecdotal evidence. In the rainforest, it is common to suddenly discover leeches high up on one’s body, arms, neck, shoulders or even in one’s eyes. Were the observers finding the leeches that had fallen from the vegetation and simply assuming that the creatures could jump?
After Dr. Fahmy shared her first leech video with other people, most of whom recognized the dance immediately. When she and Dr. The gesture seems to be a gathering of energy, a preparation for what will come next – flight and an uncoordinated, almost rapid landing.
In fact, they found that this particular sequence of movements—bend, jump, end with a belly kick—is not uncommon among other jumping worm-like organisms, including caterpillars and fly larvae.
The way the leech falls to the forest floor in the 2017 video, with very little apparent control of its descent, seems to be common among these creatures. It is possible, said Dr. Tessler, that because larvae, caterpillars and leeches are very light, they do not need a precise landing to avoid injury.
In 2023, Dr. Fahmy was back in Madagascar and she took out her phone to film a pair of leeches on a leaf. Within seconds, she was seeing the same movement again—one of the leeches gathered and rose into the air. She and Dr. Tessler identified the leech species in both videos as Chtonobdella fallax, a member of a larger family also found in the Seychelles, Southeast Asia and the South Pacific islands..
Fahmy was able to capture these videos without much planning, suggesting that jumping may be regular behavior for some leeches. Researchers hope other people can come forward and film more acrobatic bloodsuckers. Perhaps one of the problems that prevented the identification of the leech dance all these years was the lack of people with cameras.
However, Dr. Fahmy and Dr. They will start the leech version of running, a frantic inchworming together, in an attempt to get closer to you.
“It can be very frantic,” said Dr. Fahmy. “And when there’s a lot of leeches, it can be kind of overwhelming on the field to find yourself being chased so intensely by so many little guys.”
“They book it,” added Dr. Tessler. “It can be pretty wild.”