A Leech Leap

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In 2017, Mai Fahmy was studying leeches in Madagascar’s rainforests for her PhD, when she saw some extremely bizarre behavior.

While observing a single leech on a leaf, Fahmy noticed that the limbless creature contorted its body in a peculiar way – and proceeded to jump from the foliage.

She returned to the island again in 2023 and confirmed what she only suspected: At least one species of leeches is able to jump, she and her colleague Michael Tessler wrote in their study for the journal Biotropica.

The team explained that Chtonobdella fallax species in Madagascar has shown this ability. Video recordings show the annelids coiling their bodies similar to a spring and launching themselves forward – just like a striking cobra.

“(The movement) is intentional, energetic and consistent in the way it coils back and jumps forward,” Tessler told Scientific American.

The researchers believe that this ability evolved in the terrestrial leeches to move quickly from elevated places to the ground or reach hosts more effectively. Unlike the passive ambush techniques typically associated with leeches, jumping suggests a more active approach to seeking out its victims.

While the videos only don’t show leeches leaping on their victims, it adds to the further body of evidence – albeit anecdotal – that there could be other species pulling these jumps.

“There have been previous accounts of leeches jumping … but those reports were often explained away as leeches just dropping from branches or attaching to passersby as they brushed against shrubs,” Fahmy said in a news release for the Natural History Museum in London.

Jumping is not unique to leeches: Other annelids, such as earthworms in the Megascolecidae family, also exhibit similar behaviors to evade predators by curling and flicking their bodies to jump.

Both leeches and these earthworms rely on their muscular systems instead of bones to maintain rigidity and perform these jumping actions.