Much was made of Natural England’s 2014 decision to authorise the use of eDNA for determining the presence or likely absence of great crested newts. And rightly so, as if used appropriately this technique has the potential to save clients time and money.
However, the eDNA method is not without its limitations (and there are a few). These include ‘false negatives’, which can occur where only very small populations of GCN are present, and ‘inconclusive’ results which can be caused by high sediment content. Perhaps most significantly, if a pond returns a positive result then the regulators still require the GCN population size to be estimated if a mitigation licence is required, which at present can only be achieved using traditional survey methods. If not carefully factored into project planning from the outset, then this can lead to surveys being needlessly repeated.
The traditional survey method comprises using three recognised techniques to check for the presence of GCN on four (to determine GCN presence/likely absence) to six (to allow the GCN population size to be estimated) occasions. Recognised techniques include torchlight searching, egg searching, netting and bottle trapping, which is demonstrated in the short video below.