The traditional method of surveying for newts is a combination of torch surveys, bottle trap surveys and egg searching. Although these methods are widely accepted they are not without their limitations. With torch surveys, it is not easy to distinguish between newt species from a distance. Torching works relatively poorly in turbid ponds. The bottle trapping survey, while being an effective means of determining presence and species, does run the risk of being detrimental to the population as there is a proportionally high mortality rate associated with the method.
Recently, a new survey method has been posited. The new technique is called eDNA (environmental DNA), and if successfully rolled out across the country as the standard surveying technique, it could greatly speed up the process of determining great crested newt presence within a water body.
eDNA is DNA that is released by plants and animals in a host of ways: from their skin, faeces, mucous, hair, eggs and sperm, or when they die. In aquatic environments, eDNA is diluted and distributed in the water where it persists for 7-21 days, depending on the conditions. Recent research has shown that the DNA of a range of aquatic organisms can be detected in water samples at very low concentrations using qPCR (quantitative Polymerase Chain Reaction) methods.
The polymerase chain reaction is a technology in molecular biology used to amplify a single copy or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. Quantitative PCR is used to measure the quantity of a target sequence is present in a sample and the number of its copies in the sample.
A primer was developed, which is a length of artificial DNA which specifically binds to and amplifies the DNA of the target organism. This process was able to detect Great Crested Newt eDNA successfully in water samples.
Although it is quite clear that the method can detect very small amounts of DNA, it is much harder to say what the minimum number of newts is that can be detected. This is because it is difficult even using conventional methods to say how many newts are present in a pond without very intensive mark and recapture studies. In practice, during the breeding season, the technique was able to detect newts with DNA in ponds which had torch or bottle trap counts of just 1 or 2 animals, and sometimes when no animals were recorded.
Overall, collecting eDNA appears to be a highly effective method for determining whether great crested newts are present or absent during the breeding season. It is not known how effective the method is outside this period and, at the moment, eDNA provides only limited information on newt abundance. However, eDNA seems to offer more certainty about zero values. Traditionally it has been difficult to say that there are no great crested newts at a pond because surveys might just have missed them.
The eDNA technique is substantially quicker than traditional methods.
A detailed sampling and analysis protocol has been devised and, providing this is followed, both Natural Resources Wales and Natural England will accept eDNA test results as evidence of presence or absence. Water samples need to be gathered between 15 April and 30 June and sent to a recognised laboratory for analysis. The possibilities for similar techniques to detect other protected species mean that this is currently a very exciting field to be involved in.
ADAS has produced a video demonstrating the correct technique for undertaking environmental DNA testing for Great Crested Newts.
If you would like to learn more about the eDNA technique or get involved in testing the technique visit the Freshwater Habitats Trust website. Acer Ecology has extensive experience in great crested newt survey and mitigation, as well as applying for European Protected Species Licences.
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