Scientists have uncovered video evidence that at least one species of terrestrial leech can jump.
This behavior has been debated for over 100 years, and can now be put to rest following research by scientists from the American Museum of Natural History, Fordham University, and City University of New York (CUNY)'s Medgar Evers College, published in the journal Biotropica.
The discovery offers new insights into the behavior and ecology of these often-overlooked, blood-sucking creatures.
"We believe this is the first convincing evidence that leeches can jump and do so with visible energy expenditure," lead author Mai Fahmy, a visiting scientist at the Museum and a postdoctoral researcher at Fordham University, said in a statement. "There have been previous accounts of leeches jumping, including onto people, but those reports were often explained away as leeches just attaching to passersby as they brushed against shrubs or dropping from a branch above. This study dispels that argument."
"If we can identify how leeches find and attach to hosts, we can better understand the results of their gut content analyses," Fahmy said. "Leeches are also often overlooked and understudied, and, as a natural part of the ecosystem, leeches themselves may be in need of conservation protection."
The finding was made during two expeditions to Madagascar across 2017 and 2023. Fahmy videoed footage of Chtonobdella leeches—which are terrestrial rather than marine or freshwater leeches—coiling back on a leaf and then launching themselves into the air.
The researchers compared this motion to a "backbending cobra," or a spring being pulled back. The leech keeps its body extended as it jumps, differing from their typical inchworm-like movements.
"Essentially, it executes a graceful jump but with a seemingly hard landing," coauthor Michael Tessler, an assistant professor at CUNY's Medgar Evers College and a research associate at the Museum, said.
While other creatures such as the legless larvae of gall midges, Mediterranean fruit flies, "skipper flies," and some caterpillars can jump, concrete evidence of terrestrial leeches' ability have been very scarce.
"We do not know how often this may happen, or whether these leeches use this ability to seek out hosts, but, given that we caught multiple jumps in two short recordings, this behavior may be common for this species," said Tessler, who has extensively studied leeches as a graduate student in the comparative biology Ph.D. program at the Museum's Richard Gilder Graduate School.
Fahmy collected the jumping leech during the 2023 expedition and identified it as Chtonobdella fallax, a species common in Madagascar. The Chtonobdella genus is widespread across Madagascar, the Seychelles, the Malay Archipelago, and the South Pacific Islands.
The discovery of jumping leeches adds a new dimension to our understanding of these creatures and their ecological significance. As researchers continue to explore the behaviors and interactions of leeches within their ecosystems, such findings will undoubtedly contribute to a deeper appreciation of the complexity and diversity of life on Earth.
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