Using Leeches To Find Bigfoot

A new paper in Current Biology suggests leeches can be used as a cheap way to track rare mammals. The research found that the presence of mammals can be determined by testing the victim's blood for DNA stored in the leech. The blood may survive a year-and-a-half.

For researchers looking for evidence of Bigfoot, this new study shows that you don't need expensive trail cameras to track elusive creatures like sasquatch. Leeches may not only provide clues about where to look, they can also provide valuable blood samples that can be used to identify unknown animals.

Here's an excerpt from an article that was published about the paper:

[...]
So long as there are leeches that feed on the blood of animals, Gilbert says the method could prove invaluable. It's possible leeches could be used to see if well-known endangered species, like tigers or rhinos, still roam various little-explored forests in Asia.

Leeches could even help cryptozoologists (literally those who study "hidden animals") explore the presence of long-believed extinct animals. For example, most scientists believe the Tasmanian tiger (Thylacinus cynocephalus) has been extinct for decades, but unconfirmed sightings of this large marsupial carnivore persist in Tasmania, Australia, and even on New Guinea. Could leeches, which are found both on land and in water in Tasmania, show whether the Tasmanian tiger still roams the wild?

"Absolutely," Gilbert says, "if [leeches] like to eat Tasmanian tiger. It's something we hope to explore. The nice thing of the method is we can look at a generic DNA marker [so] we don't have to pick a species up front. We can just say 'let's see what mammals are there.' The point being, we could go to Tasmania, collect leeches, look at the total mammals in the area, and maybe hit lucky."

And that's not it. Gilbert says DNA found in the leeches could point researchers to new species as well. He explains: "If the leeches eat the animal, and we sequence it, we will find two results. Either a sequence that is known, or an unknown sequence. With mammals, if it is the latter, it will probably be similar enough to something else to give a hint (e.g. some kind of cat, some kind of rabbit). What one then has to do is look at two options. Number one: it's a discovered species that hasn't yet been sequenced - to check this we find candidate animals, sequence them, and see if the sequence matches. Or number two: it's an as yet undiscovered species. Here we can only give some rough description [...] we can say, 'hey we think there is some kind of unknown cat in the area.' We can't of course be more specific, but that's the point of other methods."

So, not only could the leech help determine whether a species is gone for good, but it might be able to tell us where to look for a new species, and what to look for (cryptozoologists interested in animals based on local sightings and folklore, such as the Sasquatch of North America or the orang pendek of Sumatra, might want to take note).

The leeches tested in the Annamite Mountains were terrestrial leeches, but Gilbert says that aquatic leeches could also be tested for other animals, including fish, reptiles, and amphibians. Of course, the method in every habitat is limited to those species that leeches feed on, but it also appears to be limited to the leech's last meal. Gilbert says that DNA from past meals are quickly overwhelmed by new blood, making DNA from old meals, or multiple ones, improbable to detect.

But leeches are not the only animals that suck blood. Researchers are already working with similar DNA-extracting methods with mosquitoes, and ticks may be next. But Gilbert says the advantage of leeches is that they retain blood for so long. Still each bloodsucker may target its own set of victims.

"We don't now if the leeches have dinner biases, it may be that such biases need to be considered," Gilbert says. In the future, such work may be able to tell researchers even more than whether or not an animal is in the area, it may also be used to answer the important question of how many of these animals are left. Gilbert explains that scientists are currently exploring what blood DNA from leeches may say about abundance.

As for the saola, Robichaud says his group is moving forward on trying to track the elusive animal byway of leeches, calling the work "very exciting." However he adds that the documenting the species, which is listed as Critically Endangered by the IUCN Red List, will still depend on multiple strategies, from camera traps to possibly dogs.

"Until the efficacy of the leech method is demonstrated, and its strengths and weaknesses understood, we'll keep pursuing all tools we have available," Robichaud says.

Such strengths and weaknesses will become clearer as more research is conducted.

"We are kicking off other studies in various parts of Southeast Asia and Madagascar," says Gilbert. "We hope others will too once they realize its really quite easy and cheap!"

It may not be long before the leech becomes key in saving its victims from extinction.

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