The rare sand lizard is being reintroduced to dunes in Denbighshire after a successful breeding project.
The lizard likes to sunbathe in summer and burrow underground in winter
Shy and difficult to spot, wildlife experts hope the lizard will be repopulating its former stronghold.
About 100 of them have been bred in captivity at Chester and Jersey Zoos as well as in a back garden in Sussex.
It follows the success of similar projects in Flintshire and parts of Gwynedd, with their reintroduction starting in 1995.
Liz Howe, species expert at the Countryside Council for Wales said: "The exact location is being kept secret at the moment to make sure that the lizards have time to adapt to their new surroundings.
"The project has been a resounding success over the past decade.
"We've seen numbers increase strongly, as the lizards are now breeding naturally. We also know that they are extending their range as they move further from the reintroduction areas."
But she said it was important to continue introducing young lizards for some years to come, to establish a population with a good age range and genetic variation.
The sand lizards, although active during the day, are very shy and difficult to spot.
Even in good weather they will spend much of their time under cover but can sometimes be seen sunbathing on patches of bare sand.
It is the rarest of the three types of native lizards found in Wales, and became extinct from the dunes of north and west Wales in the 1960s.
Reintroduction started in 1995 when young sand lizards, bred from adults captured on Sefton Coast on Merseyside, were released to suitable dunes in north west Wales.
Adult lizards not only need thick vegetation where they hide and feed in daytime, but also barren areas where they can lay their eggs.
They burrow into the sand dunes to hibernate in winter, which is why some of the Welsh coasts were home to high numbers in the early decades of the last century.
Gary Davies of Denbighshire council's countryside service said: "It is a great loss when any species, large or small, is pushed into extinction for whatever the reason."
Sand lizards are considered vulnerable across north west Europe, but are unmistakeable when seen.
They have a series of dark blotches and lighter coloured stripes that run down the back, and the bright green flanks of the male are striking during the breeding season.
These males, which can grow to 20cm in length, fight vigorously for females.
They grab the neck of their opponent with their jaws and then roll over and over each other, until one, usually the smaller lizard, retreats.