NUMBERS of one of the UK's rarest reptiles are on the rise at Studland, the latest ecological survey suggests.

National Trust volunteers spent a year on the peninsula mapping the distribution of reptiles - including the elusive smooth snake.

Smooth snakes in the UK are limited to parts of Dorset, Hampshire and a small pocket in Surrey. The entire population is thought to number only a few hundred, of which an estimated 50 live in Studland.

The trust says numbers of smooth snakes have almost certainly increased since the first detailed ecological surveys of Studland in the 1930s.

National Trust ecologist Michelle Brown said: "Studland is on the frontline in the battle to protect smooth snakes, as it is for many other species.

"The information gathered by our dedicated volunteers means we are better able to preserve the delicate balance which makes this place so special."

Studland is a nationally important site for reptiles because all six native British species live there. The smooth snake is the rarest of them all.

The snake's population growth is thought to be due to the growing maturity of the heathland at Studland, which is managed as a national nature reserve.

Reptile surveys take place between spring and autumn when the creatures are active and take a break over the winter when they hibernate.

A National Trust spokesman said: "Early autumn is an important time for reptiles when they need to build up enough body fat to see them through the winter months, which they spend in a state of ‘torpor’ or suspended animation.

"Smooth snakes often use abandoned mammal burrows as their winter homes.

"Rangers use winter as an opportunity to improve the habitat while the reptiles are safely underground, for instance by creating open areas where they can bask in the sun or lay their eggs."

Information on reptile distribution gathered by the volunteers is important in determining the best places for these ‘scrapes’.

"However, care needs to be taken to avoid promoting one species at the expense of another," said the trust spokesman. "For instance, too much gorse is bad news for smooth snakes which need open areas to bask, but some gorse helps provide a habitat for other rare species such as the Dartford warbler."