This Weekend, Water Voles Are Making A Splash In England

By Russell Newlove

Published August 19, 2016 at 5:03 PM EDT

About 100 water voles are being reintroduced at Malham Tarn, a lake in North Yorkshire in England. This is the first time the endangered mammals have been seen in the area in 50 years.

The water vole — once a common creature in the British countryside — hasn't been seen in the U.K.'s Yorkshire Dales for more than 50 years. But starting this weekend, the endangered animals might be making a comeback.

Arvicola amphibious has a fine literary pedigree: In The Wind in the Willows, "Ratty" was in fact a water vole. The furry-tailed, water-loving rodents were once in abundance in the Yorkshire Dales but have been eradicated by industrialization. Blame minks, too. Ecologists believe that the predatory critters, escaped from fur farms, devastated vole populations.

In recent decades, voles are thought to have disappeared from some 90 percent of the waterways they once inhabited across the U.K. Between 2004 and 2011, their numbers dropped by more than one-fifth.

The little guys gained the sad title of the U.K.'s fastest-declining wild mammal. Something had to be done.

Ecologist Coral Edgcumbe holds a water vole. Water voles were once a common sight in England, but numbers have dropped by almost 90 percent in recent years.

That's why on Friday the National Trust, a conservation charity in the U.K., released 100 water voles at Malham Tarn, a lake sitting just over 1,200 feet above sea level in the Yorkshire Dales in northern England. Media reports in England are calling it the biggest-ever attempt to save the endangered creature.

The National Trust bills it as the highest upland water vole reintroduction project by altitude ever carried out in Britain. They hope that reintroducing the animal to the wetlands will increase biodiversity in the area — rare plants can flourish around voles' burrows. They are also a tasty snack for predators with population problems of their own, such as owls and otters.

Releasing the voles is a steady process. Initially confined to large cages at the water's edge, they'll be coaxed out after three days with the promise of food left floating on rafts — in this case, apples and carrots. After five days, the cages will be removed and the voles will be at the mercy of nature.

Exposure to predators means the average water vole has a life expectancy of just five months. Those bred in captivity can enjoy up to three long, otter-free years. As such, the National Trust does not expect the population to change significantly for at least a year. They don't know what an ideal population size in the region should be, but they'll be monitoring the animals closely.

Prolific breeders, female voles can produce five litters every year, each time squeezing out as many as eight pups.

It will take time to reintroduce the voles. For the first two days, the animals will remain in cages on the fringe of the tarn.

Ecologists at the site say that if the reintroduction is successful, they'll return in 2017 with another 100 voles.

Russell Newlove is NPR's London producer.