Tracking the new releases

Four organisations are working together to try to restore the voles to areas where they once thrived.

The four are the Environment Agency, Mammals Trust UK, Oxford University's wildlife conservation research unit, and the Wildfowl and Wetlands Trust, owners of the LWC.

The 24 water voles being released over the next few days were born and bred at the Wildwood Discovery Park in Kent.

It breeds other endangered species for eventual release, including red squirrels, sand lizards, dormice, wild cats, pine martens and beavers.

The park's Kathy Holder told BBC News Online: "Voles aren't difficult to breed. We really just leave them to it.

"They have up to four litters a year, with from four to six young in each litter. We have 30 breeding pairs, so we'll soon have plenty of voles."

The first batch to come to the LWC will be put in acclimatisation cages placed near the centre's reedbeds. They are expected to leave the cages within a few days and to dig themselves proper burrows.

Heron alert

They will be fitted with radio collars, and researchers will monitor their movements for several hours each day, seeing what sort of areas they choose. Their findings will help with future releases.

There is nothing to stop the voles leaving the centre's grounds, though everyone hopes they will stay put.

Martin Senior of the LWC told BBC News Online: "We don't think they will disperse. The Thames flows nearby, but its banks are not suitable for burrowing.

"This is a mink-free environment, though there are herons and foxes, both of which also prey on voles."

Voles cling on in south-east England

Over the next few weeks many more voles will be released at the LWC, making a total for the scheme of 250 animals or more.

After that there are hopes of reintroducing the animals to other parts of south-east England where they were once abundant.

Alastair Driver, of the Environment Agency, told BBC News Online: "Because we restore a lot of habitats, we're keen to see the species that belong there reintroduced.

Implacable mink

"I'd like to see water voles come back to urban and suburban areas where they lived before, and to the wider countryside.

"But the mink are the limiting factor, and controlling them is labour-intensive.

"I don't think it's worth trying to bring the voles back except to reserves, or to specific river catchments where the mink are under control."

Photos courtesy of Martin Senior/Wildfowl and Wetlands Trust