UNIVERSITY OF COPENHAGEN, DENMARK AND ANNAMITE MOUNTAINS, VIETNAM. Using leeches in an effort to survey the population of an endangered antelope species–saola(Pseudoryx nghetinhensis)

Scientists have found a unique opportunity to find one of the world’s rarest mammal by using the DNA of leeches.

Thomas Gilbert, a geneticist from the University of Copenhagen, changed the course of surveying biodiversity from using camera traps to DNA. He and his colleagues fed goat blood to medicinal leeches (Hirudo spp.) by filling condoms with blood and warming them under heat lamps. After several months, they identified goat DNA in every one of them .

In another part of the world, Nicholas Wilkinson, a wildlife ecologist based in Vietnam worked for WWF. He had been surveying the Annamite Mountains, which border Vietnam and Laos, for the elusive saola antelope. He had already given up the conventional surveying with camera traps and trained dogs to hunt because it failed to find the saola and cost a whopping $400,000.

Bringing together these two great men of science, Wilkinson sent samples of the tropical leech (Haemadipsa spp.) to see whether Gilbert’s experiment is effective in surveying wild mammals. The genetics team did not find any saola DNA but found other mammal species: the Truong Son muntjac deer and the Annamite striped rabbit. Both these species were considered “data deficient” by the International Union for the Conservation of Nature (IUCN).

“It is a very easy way to get a snapshot of what animals are in the area” says Gilbert. Leeches are never the elusive kind. Scientists in the tropical field just peel them off from their clothes. It is a cheaper alternative because DNA from hundreds of animals can be generated from a single run.