A housing development was halted for seven months by hibernating slow worms.

The colony forced Downland Housing Association to delay building 19 houses and 27 flats at a site off Forest Road in Midhurst, after they were discovered by ecologists carrying out a survey in spring last year.

Slow worms, which can grow up to 35cm in length, look like snakes but are actually legless lizards. They are protected under the Wildlife and Countryside Act 1981.

Operation Go Slow began in April and so far about 300 slow worms have been found and taken to a two-hectare habitat at nearby Cowdray Park.

Leslie Hoult, development project manager for Downland Housing Association, said slow worms had already been found at another development site in Chichester.

She said: "You can't move the reptiles during their hibernation period, which is from September to March, depending on the seasonal weather changes.

"It was a surprise but not completely unexpected as we have encountered the colonies before.

"When we purchase land for development we always carry out an ecological survey, among other surveys, and this was when the slow worms were confirmed.

"They like to bask in open fields and grass and hide under rocks and logs so the site has attracted them.

"Removing them has held up the development slightly but we are more than happy to protect the wildlife."

Ecologist Chris Johnston, of Thurlow Countryside Management, is overseeing the removal of the slow worms.

He said: "Slow worms are protected because they are in decline and it is illegal to kill or injure them.

"Usually we would be able to move them along the site and then build but in this case there was no habitat left here for them.

"We have built a fence round the site and we are half way through moving them. There are probably up to 500 slow worms on the site and we hope to be finished by July or August."

The slow worms are removed by placing, tin, bits or carpet tile and roofing slates on the ground which they shelter under for warmth. This attracts them to a "hotspot where they can be easily found and removed.

Mr Johnston said: "Once or twice a day we come along to check them and we move about 15 to 30 a day.

"They are starting to come out of hiding and we have a team of two down there helping to move them."

Work on the housing development will start after all the slow worms have been removed and is set to be finished by October next year.