Environmental DNA (eDNA) is DNA which is collected from water in which plants or animals live rather than from the organism directly. A method has been developed in ponds in the UK to use eDNA to determine presence or absence of Great Crested Newts within a waterbody.
Currently, Natural England guidance that a series of four surveys (or 8 visits) to a pond is required to determine presence or absence, when the newts are breeding, usually between mid-March and mid-June. At least half of these surveys must be undertaken between mid-April and mid-May and make use of three different detection methods (preferably torch survey, bottle trapping and egg searching).
As a cryptic species, great crested newts are notoriously difficult to detect and results published in the 2014 paper ‘Analytical and methodological development for improved surveillance of the Great Crested Newt, and other pond vertebrates’ found that detection rates using eDNA (99%) were higher than the traditional survey methods (95%), lending credibility to the technique.
The development of the eDNA test for great crested newts can greatly reduce the time and cost of establishing presence or absence of great crested newts within a pond. The technique only requires a single visit to a water body with no restrictions on time of day as seen with previous methods. eDNA also persists in the environment for up to 21 days and as such the test can be undertaken during a longer period between mid-April and late June.
However, should presence be detected within the pond using the eDNA analysis, Natural England still require a full population size class for a European Protected Species (EPS) mitigation licence. In these cases a full suite of six visits using three detection methods must be undertaken. Natural England also specify that at least half of these surveys should be undertaken between mid-April and mid-May.
Because of these factors, eDNA testing is most suited to projects with a large number of ponds and waterbodies, with a long lead time. This will help scope out the potential for great crested newt populations to be present and give full consideration to ecological requirements within the scheme.
Ponds with low potential to support great crested newts, but which require further investigation to confidently assess likely absence will also benefit from the reduced effort and cost involved in an eDNA analysis.