If you're wondering what types of mammals are present in a given area of wilderness, why not check for their DNA in animals that feed on their blood – leeches? That's what researchers from the American Museum of Natural History have done, with good results.

The idea of analyzing so-called invertebrate-parasite-derived DNA, or iDNA, isn't brand new – it was previously demonstrated in a 2012 study in which 25 leeches from Vietnam were examined. This time around, scientists Mark Siddall and Michael Tessler wanted to apply the technique to a broader geographical region.

In the process of doing so, their team analyzed approximately 750 Haemadipsa leeches collected from the forests of Bangladesh, Cambodia, and China. The researchers found that the leeches contained DNA from a broad variety of mammals, including muntjac deer, macaque monkeys, wildcats, porcupines, rats, and the vulnerable Indian bison.

Perhaps a little surprisingly, the team also found DNA from a species of bat, along with that of some non-mammals – three types of ground-dwelling birds.

"Our recent work has demonstrated that we can determine what mammals are in a protected area without hunting, without trapping, without the use of scat or hair samples, and especially without camera traps – all of which are problematic methods for one reason or another," says Siddall. "Instead, by sequencing the host DNA that remains inside of terrestrial jungle leeches for months after feeding, we can out-perform all other methods of biodiversity monitoring in terms of accuracy, completeness, speed, and cost. We even get the small mammals that most other methods miss."

A paper on the research was recently published in the journal Systematics and Biodiversity.