Blood in Leeches Helps Save Species

Traipsing around a field site in Malaysia, Mads Bertelsen, a biologist with the Copenhagen Zoo, noticed leeches glued to his colleague’s body. Rather than grossing him out, it got him wondering: Could he collect DNA from blood consumed by leeches to find out which species they fed on? If so, he thought, it could provide a simple, inexpensive way to track species and help pinpoint critical habitat. Turns out, he was right. 

Bertelsen and one of his colleagues, Thomas Gilbert, showed that the genetic material stayed intact in the bloodsuckers for weeks. When they analyzed the blood in 25 leeches from a field site in Vietnam, Bertelsen and colleagues were able to identify three poorly understood species and two recently new to science: the Truong Son muntjac, a deer discovered in 1997, and the Annamite striped rabbit. They also found an animal that is difficult to monitor without physically trapping it, the small-toothed ferret-badger, the smallest badger of its kind, as well as the elusive mainland serow, a medium-sized goatlike animal.  

“Without this info we simply don’t know where animals are, thus how threatened they are and what conservation priorities need to be made,” says Gilbert, a biologist with the Center for GeoGenetics at the Natural History Museum of Denmark and a coauthor of the study, published in Current Biology.  

Employing leeches to monitor species is just one example of how conservation biologists are increasingly using genetic material from unconventional sources to determine species’ populations and ranges. Scientists have also collected DNA from snow leopard droppings to determine the animal’s diet; from permafrost and the tropics to reconstruct plant habitats; and from Chinese medicine to prevent the use of endangered plants and animals.

“With DNA, [species identification] is much faster, it’s cheaper, and it’s much more precise,” says Pierre Taberlet, a geneticist at Joseph Fourier University in Grenoble, France, who researches DNA to get a fix on cat diets and plant communities. “It’s a way to know more about the biology, and then design better conservation strategies.” As the saying goes, you can’t save what you don’t know.