Environmental DNA (eDNA) is a method to determine Great Crested Newt (GCN) presence or absence in ponds. In 2014, Natural England, approved the technique in which DNA is collected from water in which plants or animals live, rather than from the organism directly. In aquatic environments, great crested newt DNA is distributed though the dilution of urine, faeces, shed skin, hair, sperm and saliva. It can persist in the water for 7-21 days where it can be collected, typically at the same time that a Habitat Suitability Index (HSI) assessment of the water body is carried out.
In order to conduct the test only one site visit is required, during which six water samples are taken from each pond should be collected by licensed and trained personnel. The samples can be carried out between 15th April and 30th June. Samples will then be sent away to be tested in the laboratory where they may take up to three months to be processed, although some samples have been returned in two weeks. If the eDNA results show great crested newts to be present, Natural England will still require a population size class to be established in order to show the level of mitigation required for a European Protected Species Development Licence. Natural England specify that at least half of these surveys should be undertaken between mid-April and mid-May.
The benefits of eDNA testing
The technique offers a cheaper and faster alternative to conventional survey methods, which will also extend the period for surveys until the end of June. The eDNA test can be used to confirm or reject the presence of GCN within a water-body and can detect small populations which may not be picked up by the standard survey. Using eDNA to determine presence or absence should be quicker and help prevent delays in planning. Detection rates using eDNA (99%) are also higher than the traditional four-survey methods (95%) in establishing the presence of GCN in a waterbody.
The limitations of eDNA testing
The technique provides an additional means to determine presence but does not provide any estimate of GCN population size class. If results do take more than two weeks to return, there’s a possibility that population size class surveys would not be able to commence before the beginning of May, which does not allow sufficient time to fit in three appropriately spaced out surveys between mid-April and mid-May. Developers would risk the potential delay of planning applications until the following year if great crested newt presence was detected at such a late date.