White men cannot jump, but ground leeches can. This is now a scientific fact; After centuries of anecdotal reports, the parasites were captured on video jumping from leaves in Madagascar’s rainforests.

The footage was first captured in 2017 by Mai Fahmy, now a researcher at the American Museum of Natural History. She had the opportunity to encounter a leech that extended its body in search of a host, a behavior known as “searching.” The adventurous leech is found in Ranomafana National Park in Madagascar.

Fahmy took out her phone and took a picture of the leech moving forward, then jumping off the leaf, and landing with one or two strikes on the forest floor. The footage was, along with a 2023 video showing the acrobatics published today in Biotropica.

“Even though I was in the field in Madagascar collecting leeches for blood meal analysis, the pressure was on to try and see if we could get another video that supported the claim we made in the paper,” Fahmy said. With the publication of the research, the team has validated the anecdotal evidence that terrestrial parasites (at least the species) Chtonobdella are deceptive) jumps in search of a warm, blood-filled morsel to feed on.

Two leeches on a leaf, one of them jumping, in a 2023 video.
GIF: May Fahmy

Jumping leeches even entered the records of the famous 14th-century explorer Ibn Battuta, who documented the behavior of leeches in Sri Lanka, suggesting that the behavior may have evolved independently in various terrestrial leeches. But by the mid-20th century, the idea of ​​leeches jumping was viewed more skeptically in scientific publications.

“A lot of the history of this basically boils down to this question: What exactly is a jump?” “For hundreds of years, there have been anecdotes from very well-trained observers about jumping on leeches,” Michael Tesler, an invertebrate zoologist at the American Museum of Natural History and Medger Evers College, said in a phone call with Gizmodo. “It wasn’t until people started studying leeches more seriously, in about the 19th and early 20th centuries, that almost all the leeching biologists who spent time studying these things said, ‘There’s no way they can’t jump.’

It was no secret that leeches sometimes fell onto their host, but the question on the table was about intent: Do leeches expend energy launching toward a particular target (or simply into the air), or do they flip over, allowing gravity to work toward the target? they? Now, video evidence documents the parasites doing the first thing, turning around and then charging forward into the unknown. The animals are certainly moving outward from their leafy launching pad, and perhaps even slightly upward, the team says. In other words, they jump.

Fahmy and a leech on her face.  Leeches often land on their hosts from above in Madagascar.

Fahmy and a leech on her face. Leeches often land on their hosts from above in Madagascar.
picture: Maria Donohue

Leeches likely jump while searching for a host, Tesler said. After seeking movement or heat from a potential meal, animals may make a leap of faith toward the host.

Fahmi has been bitten by leeches before, including at least one instance of one of the parasites falling into her eye. Leeches like to go to the eyes, she said. When captured, samples of the animals’ blood meals can be taken to identify the animals in the rainforest. The leech is basically mobile Environmental DNA laboratory.

“I will be returning to Madagascar for years to come,” Fahmy said. “I’ll keep my eye on leeches. We know so little about their biology, natural history, and behaviors. They’re full of mysteries.”

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