15 European beavers were released into the wild in 2009 but the annual report of the Scottish Beaver Trial says that only 9 were believed to still be alive in the release area by June 2010.
The beavers were released with radio tags attached to their tails, some of which have fallen off. Other beavers have been hard to track because of the dense forestry, steep hillsides and complicated network of rivers and lochs. The monitoring relies on radio signals which are difficult to pick up in the terrain of the release site. The researchers have also used trapping to count and assess the beavers. Since the start of the project, two of the released beavers are known to have died in the wild and another, which was withdrawn from the project also died in captivity, all three beavers known to have died were male, and three females are currently classed as missing.