First conclusive evidence that a terrestrial leech species can jump

A new study presents video evidence that at least one species of terrestrial leech can jump, behaviour that scientists have debated for more than a century, published the footage and corresponding analysis in the journal Biotropica.

During two separate expeditions to Madagascar in 2017 and in 2023, lead author Mai Fahmy, a postdoctoral researcher at Fordham University recorded footage of leeches from the genus Chtonobdella coiling back on a leaf and then taking off. The researchers compare this motion to a “backbending cobra,” or to a spring being pulled back. In both cases, the leech keeps its body extended as it soars through the air to the ground, in a notable departure from their usual inchworm-like movements.

Several other worm-like invertebrates can jump, including the legless larvae of gall midges which assume a loop posture before propelling themselves into the air, the larvae of Mediterranean fruit flies, “skipper flies” and several caterpillars, including Lymantria monacha and Orgyia leucostigma. While naturalists and leech biologists have long argued about the ability of terrestrial leeches in the family Haemadipsidae to jump, with some making observations of leeches leaping in their travel notes, there has been little concrete evidence until now.

The lead author collected the jumping leech and identified it as Chtonobdella fallax, a common species in Madagascar. Understanding overall leech behavior is also important to conservation efforts because leeches — and more specifically, their blood meals — are increasingly being collected to survey vertebrate biodiversity.