some leeches jump. They coil their bodies like cobras

Not a lot of people like leeches. We literally use the word as a metaphor for someone who sponges off of other people. But despite their repellent nature, at least their very slow, snail-like movement makes them a lot less menacing. However, a startling revelation from biologists trekking through the jungles of Madagascar suggests these blood-sucking parasites are a lot more athletic than meets the eye.

Caught on camera

Mai Fahmy, a postdoctoral researcher at Fordham University and visiting scientist at the American Museum of Natural History, captured a video in 2017 showing a terrestrial leech, atop a nearby leaf. The 10-second clip then shows how the leech coils itself into a comma shape — exactly like a freaking cobra — before leaping through the air in a quest for blood, only to make an ungraceful headfirst landing.

In 2023, Fahmy was back on another field trip in Madagascar’s Ranomafana National Park when she noticed a pair of leeches idling on a leaf. She pulled out her phone on a whim to film the pair when she noticed the jumping behavior again.

Believe it or not, Fahmy’s footage is the first direct evidence of a leech performing a leap. You probably couldn’t tell by how easy it was for the researcher to film it. Such behavior had been suggested previously, the earliest known mention being by biologist Ernst Haeckel in 1881.

However, this anecdotal evidence was never taken too seriously. There’s even a ‘great debate’ among biologists in the know, although you need a couple of years studying invertebrates to hear about it. The debate hinged on what exactly constitutes a “jump”: intentional leaping versus simply falling onto a host from somewhere higher up like a canopy.

Well, now the great debate has been put to rest — at least some leeches can jump, and the world is a lot more interesting (and scary) because of it.

A leap of faith

In a new study, Fahmy and her co-author, Michael Tessler, a leech biology specialist at Medgar Evers College, analyzed the leech’s movement. They identified the leech species in both videos as Chtonobdella fallax, which is also found in Seychelles, Southeast Asia, and the South Pacific islands.

Upon analyzing the leech’s movement, the two researchers observed that the leech curls in a manner reminiscent of a cobra coiling before a strike. This curling motion appears to be a way of gathering energy in preparation for the jump, which both times concludes with an uncoordinated, almost comedic landing.

Their research revealed that this sequence of movements — curling up, jumping, and finishing with a belly flop — is common among other worm-like organisms that jump, such as caterpillars and fly larvae. The biologists believe that because larvae, caterpillars, and leeches are very light, they can land without precision and still avoid injury.

The ease with which Dr. Fahmy captured these videos suggests that jumping might be common behavior for some leeches. The researchers hope others will film more acrobatic leeches, as the lack of such recordings may have delayed the recognition of leech leaping behavior for years.

The findings appeared in the journal Biotropica.