Great Crested Newt Surveys

The methodology for great crested newt surveys varies depending on the specific objectives. Common survey methods typically involve the investigation of waterbodies within a 250-500m radius of the development site.

The selection of waterbodies for survey considers factors such as habitat connectivity between the site and surrounding waterbodies, the scale of the proposed development, the potential for impacts on great crested newts, and the feasibility of accessing waterbodies, which may be located on third-party land.

Habitat Suitability Index

Habitat Suitability Index (HSI) assessments often serve as the initial stage of field surveys for great crested newts.

HSI is a standardized method used to evaluate the suitability of a waterbody for breeding great crested newts. It involves assessing ten key characteristics (indices), such as size, shading, depth, and vegetation profile, during a daytime survey. Each index is assigned a value between 0 and 1, and these values are combined to generate an overall HSI score. This score categorizes the waterbody's suitability on a scale ranging from poor to excellent.

It's crucial to note that HSI does not directly determine the presence or absence of great crested newts. A low HSI score does not definitively rule out the possibility of their occurrence, as these amphibians can occasionally inhabit even poor-quality ponds.

Environmental DNA Testing

Environmental DNA (eDNA) sampling involves collecting water samples from a waterbody and submitting them to a laboratory for analysis to detect the presence of great crested newt DNA.

Sampling Protocol:

  • Water Sample Collection: Twenty water samples are collected from around the entire perimeter of the waterbody. Sampling is conducted from the bank, utilising extension poles where necessary to reach open water. Sample locations are strategically chosen to maximize the likelihood of detecting great crested newt DNA.

  • Sampling Procedure: Prior to sample collection at each location, the water column is gently stirred to ensure thorough mixing. Care is taken to avoid disturbing the pond sediment.

  • Sample Transfer: 15ml of each water sample are transferred into six sterile sample tubes. The water sample bag is thoroughly mixed before each sample is taken, and only one tube is opened at a time.

  • Contamination Control: Stringent measures are implemented to minimise the risk of sample contamination. These include avoiding contact between sampling equipment and the ground or other potentially contaminated surfaces, and changing gloves between the initial sampling and aliquot transfer stages.

Population Estimate Survey

Where great crested newt presence is confirmed, further surveys may be required to estimate population size. Population estimate surveys typically involve six visits, each employing at least three different survey techniques. These may include:

  • Egg Searches: Careful examination of suitable aquatic and emergent vegetation for great crested newt eggs, which are typically laid on leaves and then folded over.

  • Torch Surveys: Visual surveys of the water surface at night using a torch to count observed individuals.

  • Netting Surveys: Systematic sweeps of the waterbody with nets to capture and count individuals.

  • Bottle Trapping: Deployment of bottle traps at 2-meter intervals around the water's edge at dusk, followed by collection at dawn to count captured individuals. The number of traps used will vary depending on the size of the waterbody.

Sightings of other amphibian species will also be recorded during these surveys.

The peak number of great crested newts observed or captured during any single survey visit is used to estimate population size.