This baby dragon doesn’t breathe fire Daniel Heuclin/FLPA

It was like identifying a criminal from a bit of DNA left at a crime scene. No murder mystery was solved, but researchers have found rare blind cave salamanders in five caves they were not previously thought to live in, thanks to the DNA the animals shed in water.

This extends the known range of the vulnerable salamanders and raises hopes for their long-term monitoring and conservation.

The olms (Proteus anguinus), or baby dragons as locals call them, spend their entire life in the underground waters of the Dinaric Alps running from Slovenia through Croatia and several other Balkan countries.


DNA from bits of skin that they have shed or their feces gets dissolved into their watery habitat and can be washed out of the cave. This is good news for biologists studying cave life, because most of the 7000 or so caves in Croatia are inaccessible to humans.

“Before you would only see these elusive animals if they were washed out of their home after heavy raining, or if you would actually go cave-diving,” says Judit Vörös of the Hungarian Natural History Museum who led the study. “But now we can tell just from some cave water if they are there or not.”

Olm my goodness!

Her team used a technique known as environmental DNA, or eDNA, to survey the salamanders. “This technique has been known for some time among conservation biologist, but until now it was never used for cave vertebrates,” says Vörös.

The team collected water samples from 15 caves across Croatia during the summer of 2014. They filtered 2 liters of water from each site through special paper, and then extracted the eDNA from the paper. They confirmed the presence of the salamander in 10 caves it was already known to inhabit, and detected the species for the first time in five others.

Croatian conservationists have now adopted this technique to map the olms’ habitat more precisely, and to learn more about their population genetics.

Although both caves and olms are protected in Croatia, Vörös hopes discoveries with eDNA will accelerate the protection of the ground above the caves, since olms are very sensitive to pollution and contaminants can seep into their habitat from above.

Salamander in your hands

“This is an excellent use of eDNA, but it’s just a complementary tool,” says Matthew A. Barnes of Texas Tech University. “It’s never going to replace the hard evidence of having a fish, or a blind salamander in your hands.”

In dark, cold caves, eDNA can stick around for a long time and could even get carried far from its source, leading researchers to make false assumptions about where the olms are, he says.

And little is known about the degradation rate of the olm eDNA, or eDNA in caves at all because that has never been studied in detail.

Vörös agrees the method is not perfect. She says it can detect the presence of the animals within a cave system, but not necessarily narrow it down to a particular cave.

But she says it is a good way to identify cave systems with the animals, so the team can then examine those areas in more depth with traditional methods – sending divers, for example.

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0170945

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