Joseph Fourier University researchers have detected the presence of an invasive species by analyzing its DNA, found in water samples.

They used special DNA primers (single strands of DNA that attach to target DNA so it can be copied) to amplify a part of the DNA chain that is unique to American bullfrogs, a highly invasive species in Europe.

The technique can detect DNA even in very low concentrations and could be useful in monitoring when a species first invades a particular habitat. It could also keep tabs on threatened species with very small populations.