eDNA testing is a new technique of surveying water bodies for the presence of great crested newts. The technique involves collecting a water sample from the pond in question and analysing it in a laboratory for the presence of great crested newt DNA.
The advantage of this technique is that it only requires a single survey visit to each water body to determine the presence or likely absence of great crested newts, compared with traditional great crested newt surveys that require four separate survey visits.
However, eDNA testing can only determine the presence or likely absence of great crested newts and is not able to establish population size, which is normally required if presence is found. Therefore if presence is recorded during the eDNA survey, then a further six survey visits using conventional survey methods are required and this may not be feasible within the narrow windows prescribed for great crested newt surveys. eDNA surveys need to be conducted between 15th April and 30th June and conventional surveys between mid-March and mid-June, with at least two visits undertaken between mid-April and mid-May. This means that if the eDNA test confirms the presence of great crested newt after mid-May, it will not be possible to undertake the population size class assessment survey in the same year.
eDNA surveys may be useful where a population size class assessment is unlikely to be needed; for example where all ponds are located >250m from the development site, or for projects where only a small amount of terrestrial habitat will be affected. However, in most cases traditional great crested newt survey techniques will be more appropriate.