Smooth Snake Monitoring


	Smooth Snake Monitoring Programme

	The smooth snake is the UK’s rarest native reptile, being restricted to lowland heathland areas of southern England. Its natural range shrank to Dorset, Surrey and Hampshire due to massive historical loss of its heathland habitat. However, a reintroduction programme led by the HCT has brought smooth snakes back to Sussex and several parts of Surrey and Hampshire where it had become extinct. The largest area of heathland occupied by the smooth snake is the New Forest, though it is by no means ubiquitous across the area.

	Smooth snakes are very difficult to detect without the help of survey aids such as ‘tins’ made from sheets of corrugated iron. Because they are both camouflaged and secretive, and spend much of their time under ground or concealed in vegetation, it is generally very difficult to spot smooth snakes, even when they are basking. However, when sheets of metal are pressed close to the ground, smooth snakes readily take refuge under them in order to absorb the warmth of the metal as it heats up during the day.

	There are approximately 160 smooth snake populations in southern England, but it is very difficult to discern where one end and another one begins, nor how big each population is. The HCT coordinates a monitoring programme, largely carried out by licensed volunteers, and has been gathering data for about twenty years. The volunteers make monitoring visits, sometimes many times per year in suitable weather conditions, to check tins that we have distributed discreetly throughout smooth snake habitat on many sites.

	We also hold a digital map inventory of all known smooth snake sites, with the extent of all heathland sites where smooth snakes are present. This also pinpoints the tin locations, and our Rare Species Database holds all the monitoring data. The site inventory was based on Natural England’s Lowland Heathland GIS Inventory (version 1.2), which requires significant improvement in its boundary digitisations. The inventory includes large areas of forest mapped as heathland, whilst omitting significant areas of heathland. Naturally the heathland inventory does not include areas of acid grassland, bog or valley mire that often exist next to heathland blocks. However, as these habitats could be occupied by smooth snakes, we digitised such areas and appended them to our smooth snake site inventory.

	The movement and home range of smooth snakes is difficult to predict, as some animals are apparently virtually sedentary, whilst others move large distances. We also have gaps in our knowledge of their distribution, because some sites have not been surveyed for many years. We currently have volunteers monitoring about ten sites in the Weald and Thames Basin to ascertain the full extent of the smooth snake’s range in Surrey and Berkshire. Areas of heathland within the presumed historic range of the smooth snake are targeted with survey effort. Even if smooth snakes are not found, these sites might be considered for future translocations.

	Population status is difficult to assess using the available data, even for single sites, and changes in status are virtually impossible for most sites. Hence we are trying to establish a programme of PhD research and strategic structured monitoring to learn more about detectability, population densities and habitat preferences. We know that smooth snakes tend to be concentrated in ‘hotspots’, but we can’t say whether this is due to habitat variation or differences in management, e.g. grazing and controlled burning. Monitoring in the New Forest carried out by the HCT and volunteers in collaboration with the Forestry Commission has identified distinct hotspots and extensive areas of heathland occupied by smooth snakes. Yet there are other large areas with no smooth snakes, despite numerous tins being laid in apparently good habitat and monitored over five years.