One of Britain’s most endangered mammal species is thriving down on the breezy borders of Abbey Wood and Belvedere.

The national Water Vole population has crashed so dramatically that these furry creatures would be plunging towards extinction without help from conservationists.

Numbers at Crossness Nature reserve recently received a boost when 10 females and eight males were returned to their reedbed home in the protected area after being removed in a rescue operation.

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Forty were removed from the southern end of the protected area early last year after a pollution incident caused by contractors working on the adjacent Crossness Sewage Treatment Works. The voles were rounded up and taken to safety , along with 20 more from the Great Dyke Breach West area of the reserve.

It proved impossible to trap all the voles and when plans were hatched to return the “captives” it was found that those who evaded the round-up had prospered.

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Karen Sutton, Thames Water Biodiversity Team Manager, said: “There was no way to say how many remained but pre-release surveys revealed many field signs like latrines, burrows and feeding stations from the existing population. It was difficult to determine whether there were lots of voles remaining; whether those remaining had bred prolifically, or whether they had simply expanded into the wider area now available to them. With the support of the Environment Agency as well as licensing organisation Natural England, it was decided to release a small number rather than reintroduce 40 water voles and potentially put them at risk from existing voles prepared to defend territory by fighting to the death during breeding season.”

Water Voles are wary, shy creatures. You rarely glimpse more than a flash of tail or the top of a head protruding from the water. They were much larger than I imagined when I saw their whole bodies on release day.

I mentally wished each one good luck as they disappeared with a “plop” into the water. Voles inhabit most of the reserve waterways but the protected area, which also features a double-decker hide with glass windows, can be accessed only by Friends of Crossness Nature Reserve.

Become a life member for £10 by emailing karen.sutton@thameswater.co.uk