Water vole numbers dropped by 96% in the last century

Last year Bristol Zoo Gardens released 70 water voles into the city's Royal Portbury docks.

The animals, which have been bred from stock rescued from the wild more than five years ago, are now flourishing.

On Wednesday, a further 83 water voles will be released at a new location at the dock to establish a new colony.

It is hoped the additions will help increase the chances of reversing the 96% decline in numbers suffered by the species over the last century.

The dock location was chosen for its ideal waterways and absence of American Mink. The site underlines how voles can adapt and thrive in urban environments if the conditions are right.

However, wildlife campaigners warn that, faced with a plethora of different threats from habitat loss to poisoning, numbers continue to decline dramatically.

To enable the zoo to monitor the voles' progress, some have been fitted with a radio collar.

The water voles have also been ID-chipped, allowing individuals to be identified for ongoing studies into the effectiveness of the release.

The programme has also helped to re-establish water vole communities on the Kennet and Avon Canal near Bath.