New Video Finally Proves That Leeches Can Jump

Keen observers and students of leeches will no doubt have heard about the “great debate”: Can leeches jump?

Disputed for centuries, the argument has been ended thanks to a 10-second smartphone clip recorded on a whim in Madagascar.

The video shows a leech flailing around on a leaf before curling up, as if gathering energy, and then springing off and falling onto the forest floor below.

The New York Times reports that scientists have long been skeptical of leaping leeches which dates back to 1881 when the biologist Ernst Haeckel went to Sri Lanka and witnessed them crawling on the ground as well as “springing to reach their victim.”

Publishing their findings in the Biotropica journal, Mai Fahmy and Michael Tessler explain how the leech curls like a cobra to generate its jump.

The video was filmed in 2017, before Dr. Fahmy, a postdoctoral researcher at Fordham University and a visiting scientist at the American Museum of Natural History, had heard of the jumping leech debate.

But in 2023, when she visited the African island state of Madagascar again, she once again witnessed and recorded the same movements and the leeches taking flight.

In both videos, Dr. Fahmy and Dr. Tesller identified the leech species as Chtonobdella fallax, a member of a larger family also found in the Seychelles, Southeast Asia, and the South Pacific islands.

Given how straightforward it was for Dr. Fahmy to capture these videos, it suggests that leeches jumping is a common occurrence. Dr. Fahmy and Dr. Tessler hope it will encourage more people to film prancing leeches.

However, before people start running off into the rainforest in search of leeches, know that human presence is like a magnet for leeches which are desperate to feed on blood. They may start jumping toward you.

“That can be pretty frantic,” Dr. Fahmy tells The Times. “And when there are a lot of leeches, it can be kind of overwhelming in the field to notice that you are being pursued so intensely by so many little guys.”

“They book it,” Dr. Tessler added. “It can be pretty wild.”

Image credits: Mai Fahmy