Great crested newt surveys
The great crested newt (Triturus cristatus) is the largest of Britain’s three indigenous newt species. They are black in colour with an orange and black spotted belly, and they have characteristic ‘warty’ skin, hence their other English name of Warty Newt. They are a protected species (see ‘Protection’ below).
During the breeding season (April-June), male great crested newts develop an enlarged ‘crest’ along the back and a silver streak in the middle of the tail, which they wave and flick to attract females during courtship displays.
Great crested newts are found in a variety of habitats including farmland, woodland, grassland, quarries and brown field sites, wherever there is a suitable waterbody for breeding. They prefer open water for mating displays, and typically require marginal aquatic vegetation for egg-laying. The female carefully deposits the eggs within leafy vegetation and then folds and seals it using an adhesive-like secretion.
Once the eggs have hatched, the larvae will swiftly develop and metamorphose into ‘efts’ (juveniles) over a period of three to six weeks. By August, the immature newts will emerge from the pond and continue to develop in the terrestrial environment. At two to four years of age, the newts become sexually mature, having an average lifespan of approximately eight years.
Great crested newts are carnivorous and will feed upon a range of aquatic invertebrates and the larvae of other organisms.
The main threats to the survival of the great crested newt are habitat destruction and fragmentation as a result of anthropogenic development. Emerging infectious diseases such as chytridiomycosis, caused by a pathogenic fungus, also pose a significant threat to this species.
Great crested newts and their breeding sites are protected by the EU Conservation of Habitats and Species Regulations 2010 and the Wildlife and Countryside Act 1981 (as amended).
Under Regulation 41 of the Conservation of Habitats and Species Regulations, it is illegal to:
- Deliberately capture, injure or kill this species
- Deliberately disturb this species, which refers to anything that may impair its ability to breed, reproduce, hibernate or migrate
- Deliberately damage the breeding site or resting place of this species.
Great crested newts are also a ‘UK Biodiversity Action Plan (BAP) Priority Species’, and the action plan aims to maintain and enhance populations across the UK.
Great crested newts can be surveyed between March and June using standard methods, and between 15th April and 30th June using eDNA sampling (see below for more information on this).
Following Natural England guidelines, a standard ‘presence/absence’ great crested newt survey requires four survey visits to potential breeding open water habitat. These surveys are carried out during the breeding season, which is between April and June, with at least two surveys being carried out between mid-April and mid-May. For the purpose of Natural England licence applications, if great crested newts are discovered during the presence/absence surveys, then it is necessary to determine a population size – for this, an additional two survey visits are required.
Surveys are usually carried out in the evening using a variety of methods, including torchlight surveys, netting, terrestrial search, egg search (on suitable vegetation) and bottle trapping. The latter involves placing plastic bottles set at approximately two metres apart around the margins of the waterbody. Newts are inquisitive animals and tend to investigate and enter these bottle traps. They typically remain within the trap until the licenced surveyor returns the following morning. Using bottle traps allows ecologists to record certain biometric information such as gender and life-stage, before releasing the newts back into the waterbody.
In addition to this, a recent ecology survey innovation called ‘eDNA sampling’ is now being used to detect microscopic fragments of DNA biomarkers belonging to great crested newts within waterbodies, where such fragments can persist for one to three weeks, depending on environmental conditions. This method can be used to determine species occupancy in ponds (i.e. presence/absence) and has the potential advantage of increasing survey efficiency.
For the field sampling, a trained and licenced great crested newt surveyor identifies where 20 water sub-samples are to be extracted. Particular focus is given to areas with suitable egg-laying vegetation and open water, which may be utilised for mating displays. Using a sterile ladle, 20 sub-samples of pond water are emptied into a self-supporting Whirl Pak. In order to homogenise the sub-samples (i.e. mix the DNA across the whole water sample), the Whirl Pak is subsequently shaken for approximately ten seconds.
Following the sample homogenisation, and using a pipette, 15ml of water is extracted from the Whirl Pak and emptied into six sample tubes (increasing the total volume of the tubes to 50ml). Each sample tube is shaken for ten seconds to bind any present DNA to the preservatives, thus preventing degradation. The samples are then returned to the offices for refrigeration prior to being delivered to our laboratories for the qPCR (quantitative polymerase-chain-reaction) analysis. As eDNA persists in waterbodies (excluding sedimentary deposits) for a relatively short period of time, collected samples should contain the DNA fragments of great crested newts that were recently present within the waterbody.
Support for eDNA
This technique has been supported by Natural England and, where negative results are returned following analysis, the requirement of further survey using the standard bottle trapping, egg search and torchlight methods can be omitted, thus potentially saving our clients time and money.
A recent study published by DEFRA (Department for Environment, Food and Rural Affairs) and conducted by the Freshwater Habitats Trust, showed that eDNA sampling used to determine the presence of GCN had an accuracy level of 99.3%, compared to only 76% via the standard bottle trapping technique.
To support a licence application for development, Natural England will only currently accept the results of this new sampling technique if the samples are collected between 15th April and 30th June, so planning ahead is important.