White leeches can’t jump, but land leeches can. This is now a scientific fact: after centuries of anecdotal reports, the parasites have just been captured on video leaping from leaves in the rainforests of Madagascar.
The footage was first captured in 2017 by Mai Fahmi, now a researcher at the American Museum of Natural History, who stumbled upon the adventurous leech stretching out in search of a host (a behavior known as “questing”) in Madagascar’s Ranomafana National Park.
Fahmy took out his phone and recorded the leech inching forward, leaping from the leaf and landing on the forest floor. This footage, along with a 2023 video of the leech performing its acrobatics, can be viewed here: Published Today is Biotropica.
“I was in Madagascar collecting leeches for blood meal analysis and felt pressured to get another video to back up the claims in the paper,” Fahmy said. With the publication of the study, the team confirmed that land-dwelling parasites, at least this species, Kutnobdera Falux) hop around in search of warm, bloody food.
Jumping leeches also feature in the chronicles of the famous 14th-century explorer Ibn Battuta, who recorded the behaviour of leeches in Sri Lanka and suggested that this behaviour may have evolved independently in various terrestrial leeches. However, by the mid-20th century, the notion of jumping leeches was being met with more skepticism in scientific publications.
“A lot of this history basically comes down to this question: ‘What exactly is jumping?’ For hundreds of years, very well-trained observers have told anecdotes about leeches jumping,” Michael Tesler, an invertebrate zoologist at the American Museum of Natural History and Major University College, told Gizmodo in a phone interview. “Once people started studying leeches more seriously in the 1800s and early 1900s, almost every leech biologist who studied leeches said, ‘There’s no way leeches don’t jump.’‘“
Leeches are well known to drop onto their hosts, but questions remain about their intentionality: Do they expend energy to jump up towards a specific target (or simply into the air), or do they allow gravity to take them down? Now, video evidence records the parasite doing the former, coiling up and then jumping up into the unknown. The team argues that the leeches do indeed move outwards from the leaf launch pad, and perhaps even slightly upwards. In other words, they jump.
Tesler said leeches likely jump because they’re searching for a host: After looking for movement or heat from potential prey, the leech may jump toward the host as a kind of leap of faith.
Fahmy has been bitten by leeches before, and at least once had a parasite lodged in her eye, which she says leeches like to target. By collecting blood from captured leeches, she can learn more about the rainforest animals. Leeches are primarily mobile creatures. Environmental DNA Laboratory.
“I plan to return to Madagascar for many years to come,” Fahmi says, “and focus on leeches. Very little is known about their biology, natural history and behavior. They’re a mystery.”
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