Four beaver families at the forefront of attempts to re-establish the species to Scotland have been flown from Norway to Heathrow to spend six months in quarantine before being released in Argyll in the spring.

The animals were hunted to extinction in Scotland in the 16th century, but there is now to be a trial reintroduction in Knapdale Forest.

There has been a mixed local response, with a survey last year finding that, while almost three out of four people in mid-Argyll supported the idea of bringing beaver back to Knapdale, most of those who live closest to the proposed trial sites were opposed to such a move.

The Scottish Wildlife Trust (SWT) and the Royal Zoological Society of Scotland (RZSS), project partners for the Scottish Beaver Trial, enlisted the help of a specialist team to assist them with the capture of the beaver families from the Telemark region of Norway in September.

For the past two months, the team has been capturing the beaver families, each consisting of one adult male, one adult female and between one and three yearlings or kits. Tracking the beavers and ensuring they were in the correct family groups was an important part of the process. The creatures do not have names yet and will be catalogued using numbers for the quarantine period.

Iain Valentine, RZSS head of animals, conservation and education, said: "The capture of the beaver families was a complicated process because we wanted to ensure that existing beaver families, which included yearlings and kits, were captured together. Luckily, beavers are territorial so families can be tracked within the areas they inhabit.

"The team in Norway spent long periods in specific sites to identify complete family groups, ensuring that none was left behind.

Another added complication was that beavers are primarily active at night, so the beaver families were tracked from boats patrolling the river and caught in the dark. The team in Norway did a fantastic job and all the beavers are in excellent health."

Once released, SWT, RZSS and Forestry Commission Scotland will manage the project, with Scottish Natural Heritage conducting scientific monitoring on the impact of the new beaver arrivals.

Simon Jones, the project manager, said: "Beavers are native to Britain but were hunted to extinction over 400 years ago. Beavers hold the potential to create new wetland habitats which in turn increases the appeal to other native species. We are excited to get the trial under way and really see what benefits beavers can bring to Scotland."

Environment minister Michael Russell is enthusiastic. "This is the latest stage in a truly exciting development for wildlife watchers, not just in Scotland, but around the world," he said.