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Environmental DNA (eDNA) survey

An Environmental DNA (eDNA) survey uses detectable DNA that is released by an organism and persists in the environment; in this case Great Crested Newt (GCN) eDNA remains in ponds for a short period of time in the breeding season, such that a water sample can be taken from the pond and screened for GCN eDNA via laboratory analysis to confirm GCN presence/likely absence at a pond.

Presence/Absence and Population Size Class Assessment

Surveys to establish the presence/ likely absence of great crested newts at a pond rely on four survey techniques; deploying ‘bottle’ traps overnight and subsequently counting any GCN caught prior to release, torchlight searches, searching through pond vegetation for eggs, and using a net in the pond margins.

The difference between a Presence/Absence survey and a Population Size Class Assessment is the number of surveys required. If no GCN are observed after four surveys, the total survey effort is termed a Presence/Absence survey and likely absence of GCN can typically be assumed. If GCN are observed in the first four surveys a total of six survey visits are required, forming a Population Size Class Assessment. For either survey type, all surveys must usually be completed in mid-March to mid-June, with at least half of the survey visits occurring in mid-April to mid-May.

Habitat Suitability Index (HSI)

This survey type records various environmental attributes of a pond and expresses the suitability of a pond for GCN as a single numerical index from 0 to 1, whereby ponds with a higher HSI score generally have an increased likelihood of GCN presence.

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