eDNA, or environmental DNA is genetic material given off by an organism into its environment. In the case of great crested newts, the eDNA samples are collected from bodies of water. The newt DNA is released into the water via shed skin cells, mucus, sperm, eggs, faeces and decomposing animals. Studies suggest that both the larval stage and adult stages are detectible using eDNA analysis (Rees et al, 2017; Buxton et al, 2017).
This DNA given off into the water can persist for a number of weeks, allowing us to test for its presence in water samples.