It’s the Latest in Conservation Tech. And It Wants to Suck Your Blood.

“That this bloodsucking worm might suddenly advance conservation efforts is something few would have predicted,” he said.

Terrestrial leeches are found in humid regions stretching from Madagascar to southern Asia to a number of Pacific islands. Some 70 species have been described, with many more likely awaiting discovery.

They’re a diverse bunch: some are drab brown, others strikingly patterned in greens, reds and blues. Some crawl across the forest floor in search of a meal, while others occupy leafy perches and leap onto unsuspecting hosts.


Haemadipsa zeylanica, a leech, in Malaysia after a meal. Leeches can swell to 10 times their body weight after feeding.

Bernard Dupont

They all share a taste for blood. The tiny vampires may swell to 10 times their body weight after feeding, transforming from agile, threadlike worms into engorged blood sausages. Remnants of a leech’s last gluttonous meal may remain in its body for months — a boon for researchers curious to see what it previously fed on.

The idea of using leech blood meals as an identification tool may have been inspired by a criminal case in Tasmania in 2009. Investigators recovered DNA from a blood-filled leech to link a suspect to a robbery.

Several years later, researchers published the first field study showing that the method worked to identify wildlife, too. While encouraging, the initial study was based on a sample of just 25 leeches caught in Vietnam.

Eager to see if the method might be applicable on a much broader scale, Dr. Tessler and his colleagues set out to conduct an investigation in Bangladesh, China and Cambodia.

The first step — collection — was simple, said Sarah Weiskopf, a biologist at the United States Geological Survey and co-author of the new papers: “You just get to your spot in the forest and look around for things crawling toward you.”

Of the thousands of leeches Ms. Weiskopf, Dr. Tessler and their colleagues captured, 750 were selected for genetic analysis. The researchers cut out the parasites’ digestive tracts and filtered them to extract DNA.

They used primers — short, known sequences of genetic material — to separate mammal from leech DNA, and then they sequenced the results and compared them to a genetic database of known species.

Leeches, the researchers reported in the journal Systematics and Biodiversity, are far from picky eaters: the parasites had fed on 26 different mammal species, plus three birds.

Nguyen Quang Hoa Anh, a project manager for the World Wildlife Fund in Vietnam who was not involved in the research, has been using leeches for several years to survey wildlife in remote jungles near the Lao border. He confirmed their utility as a monitoring tool, especially when paired with other methods.

“We need as much information as we can possibly get if we are going to identify endangered species and head off the extinction crisis,” he said.

Researchers have traditionally made such identifications by catching animals, collecting hair or dung samples, or setting up camera traps. Capture stresses out and sometimes injures animal subjects, however, and hair and dung can be difficult to find.

Camera traps are the current gold standard in tropical rain forests, but they tend to require significant time and expense.

In the second study, published in The Journal of Applied Ecology and led by Ms. Weiskopf, then at the University of Delaware, the researchers aimed to compare camera traps to leech collection. The researchers set up 30 camera trap sites in four forest reserves in Bangladesh and captured 200 leeches in the same spots.

While the leeches produced evidence of 12 species of mammals (including a small rodent, the Tanezumi rat, that the camera traps missed), the cameras documented 26 species. But Ms. Weiskopf pointed out that the cameras were rolling for nearly nine months, while the leeches were collected in just four days.

Simply collecting a few more leeches, Ms. Weiskopf said, could potentially put the method on par with camera trapping — especially when time and money are taken into account. The leech work cost just $3,770, while the camera traps came in at $24,800.

Given these advantages, Ms. Weiskopf said, “leeches could really complement some of our already existing biodiversity-monitoring methods, and move forward some existing biodiversity conservation efforts.”

Future studies, Dr. Tessler added, could be made even more efficient by blending hundreds of leeches into a slurry and genetically sequencing all of their blood meals in one go.

“I don’t know how big this will become, but I think leeches have quite a bit of potential,” he said. “This is just a fascinating method.”

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Trilobites: How Do You Count Endangered Species? Look to the Stars

But cameras made for daylight can miss animals or poachers moving through vegetation, and the devices don’t work at night. Infrared cameras can help: Dr. Wich had been using them for decades to study orangutans.

These cameras yield large amounts of footage that can’t be analyzed fast enough. So what do animals and stars have in common? They both emit heat. And much like stars, every species has a recognizable thermal footprint.

“They look like really bright, shining objects in the infrared footage,” said Dr. Burke. So the software used to find stars and galaxies in space can be used to seek out thermal footprints and the animals that produce them.

To build up a reference library of different animals in various environments, the team is working with a safari park and zoo to film and photograph animals. With these thermal images — and they’ll need thousands — they’ll be able to better calibrate algorithms to identify target species in ecosystems around the world.


Rhinos observed as part of the tests. The researchers found that, like stars, animals have a recognizable thermal footprint.

Endangered Wildlife Trust/LJMU

The experts started with cows and humans in England. On a sunny, summer day in 2015, the team flew their drones over a farm to see if their machine-learning algorithms could locate the animals in infrared footage.

For the most part, they could.

But accuracy was compromised when drones flew too high, cows huddled together, or roads and rocks heated up in the sun. In a later test, the machines occasionally mistook hot rocks for students pretending to be poachers hiding in the bush.

Last September, the scientists honed their tools in the first field test in South Africa. There, they found five Riverine rabbits in a relatively small area. These shy rodents are among the world’s most endangered mammals. Only a thousand have ever been spotted by people.

The tests helped the scientists calculate an optimal height to fly the drones. The team also learned that animals change shape in real time (rocks don’t) as drones fly over. And the researchers found that rain, humidity and other environmental, atmospheric and weather conditions can interfere with proper imaging.

The scientists are refining their system to account for these issues. And in two years, Dr. Burke said, they plan to have a fully automatic prototype ready for testing. Within five years, she hopes to sell systems at cost — today, just around $15,000.

In the meantime, these astro-ecologists are also working with search and rescue groups to help find people lost at sea or in fog. And starting in May, they will collaborate with conservation groups and other universities to look for orangutans and spider monkeys in the dense forests of Malaysia and Mexico, as well as for river dolphins in Brazil’s murky Amazon River.

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