Reptile survey

Six reptile species are native to the UK and are all protected under Schedule 5 of the Wildlife and Countryside Act 1981. It is an offence to intentionally or recklessly kill or injure any of them. The four common species are slow worm, common lizard, grass snake, and adder. They are widespread across England and Wales and are the species most likely to be encountered on development sites.

The two rarer species, sand lizard and smooth snake, have additional protection and cannot be handled, taken, or disturbed without a licence from Natural England. Both are primarily found on heathland habitats in southern England. Where a PEA identifies habitat that could support either species, the survey scope and the licensing requirements are more demanding than for a common species survey.

The mitigation hierarchy applies to all six species: avoidance of impact is always preferred, followed by reduction through design or working method, and compensation only where losses cannot be avoided.

Reptiles favour habitats that offer basking opportunities combined with dense vegetation cover nearby for shelter, foraging, and hibernation. The most productive habitats on development sites are rough grassland and rank vegetation with structural diversity, south-facing embankments and spoil heaps, scrub and bramble patches, linear features such as hedgerows, ditches, and old walls, and mosaic habitats on brownfield land such as railway cuttings, disused industrial ground, and allotments.

Reptiles are generally absent from dense, shaded woodland interior, intensively managed amenity grassland, and urban hardstanding. The PEA walkover identifies habitats with potential and defines the area to be surveyed. The reptile survey then targets that habitat specifically, with refugia concentrated in the areas of highest suitability.

The survey uses two complementary methods: artificial refugia checks and visual transect searches, carried out together on each visit.

Artificial refugia, typically squares of bitumen roofing felt or corrugated metal sheeting roughly half a metre square, are placed across the survey area in a grid or in clusters around the habitats most likely to support reptiles, at a density of approximately five to ten per hectare of suitable habitat. Reptiles are ectothermic: they cannot regulate their own body temperature and rely on external heat sources to warm up. Refugia absorb heat from the sun and provide a warm, sheltered microhabitat that reptiles use for basking, shelter, and refuge.

Refugia are placed at least one week before the first survey visit to allow them to settle into the environment. Reptiles that are unfamiliar with new objects in their habitat are initially wary of them; the settling-in period improves detection rates significantly.

At each survey visit, the ecologist checks under each refugia in turn, recording any reptile found and noting the species, sex where determinable, age class, and behaviour. A visual search of the surrounding habitat is carried out at the same time, recording any reptiles basking directly on vegetation or bare ground. Shed skins found during the search are also recorded as evidence of presence.

A minimum of seven survey visits are required to produce a reliable presence or absence result and estimate population size. Visits are spaced at approximately two-week intervals across the active season, and surveys should not be carried out on consecutive days as disturbance from the preceding visit reduces detection on the next.

The optimal survey windows are spring, from April to May, and early autumn, in September. These periods offer the right combination of air and ground temperatures to encourage basking activity: warm enough for reptiles to be active, but not so hot that they retreat to cool shelter underground. Mid-summer surveys in July and August are possible but are less reliable due to high temperatures reducing surface activity, and are generally used to supplement rather than replace spring or autumn visits.

For sites where the programme permits, distributing visits across both spring and autumn windows provides the most robust dataset. Where the programme is constrained to a single season, spring is preferred.

Reptile surveys are weather-dependent to a greater degree than most other ecological survey types. Visits must be carried out on days when conditions are suitable for basking activity: overcast but warm days following sunshine are often productive, as reptiles emerge to warm up quickly in the diffuse warmth. Bright, hot days in full sun are less reliable as reptiles retreat to shade early. Cold, wet, or windy days produce low detection rates and do not generate useful survey data.

The optimal time of day is mid-morning, when ground temperatures have warmed sufficiently from overnight lows but before peak midday heat. Building a weather contingency into the survey programme from the start is important: a week of unsuitable conditions can displace a planned visit by ten days or more, which affects the spacing between visits and can push the programme into a less optimal part of the season.

Where reptiles are confirmed present and development will affect their habitat, a mitigation strategy is required as part of the planning consent. The approach depends on the species found, the estimated population size, and the scale and nature of the impact.

For common species on sites with small to moderate populations, the standard approach is phased vegetation management designed to encourage reptiles to move out of the development footprint progressively before clearance begins, combined with translocation of any animals remaining in the clearance zone to a prepared receptor site. The receptor site is typically a habitat-managed area within or adjacent to the development, created or enhanced to support a viable population long term.

Reptile exclusion fencing may be required to prevent animals re-entering the clearance zone after translocation. Where the population is large or the habitat of high quality, compensation habitat of a comparable or greater extent may be required. For sand lizard or smooth snake, a Natural England licence is required before any translocation can be carried out, and the method statement must be agreed in advance.

Reptile survey pricing depends on the area of suitable habitat to be surveyed, the number of refugia required, and the location of the site. Surveys covering larger or more varied sites require more visits and more time on the ground.

To avoid losing a survey season, refugia need to be placed before the first check visit. The earlier in the season the programme starts, the more flexibility there is to accommodate weather delays without losing visits. To get a quote, provide us with your site address and the PEA report if available, or a description of the habitats present. We will confirm the survey scope, the number of refugia and visits required, and provide a fixed price.