Meet Reid - the English Springer Spaniel trained to sniff out water voles in the Yorkshire Dales

Now, after the National Park authority appointed Reid as a top detective, there is a hope he could bring some relief. The conservation detection dog, along with handler Rachel Cripps, has been scouring out the voles' hideaways to chart their numbers for official reports.

Once published, the findings could help secure funding for habitat projects and more.

Zara Hanshaw, ecologist for the North York Moors National Park Authority (NYMNPA) said a team of volunteers has been surveying the declining population since 1999.

They found evidence of water voles at only five of 23 sites, which can be tricky to access.

"As the years have gone on, we have been losing water voles," she said. "It's really hard to prove ' absence' with surveys - have they moved on or are we not looking hard enough?

"Reid is slightly less fallible than us, he can be more accurate.

"Also he has four legs, and can get into the water courses a little bit easier."

American mink have traditionally been the endangered species' biggest threat, Ms Hanshaw explained, so small they can wipe out a colony as they burrow away from threats.

But the water vole, despite its name, is not a good swimmer, she added. With habitat fragmentation, and sudden rises and falls in water levels, they have struggled.

"We have still got them," she said. "We just have less and less as the years go by."

A full report on Reid's findings will be delivered in March, funded as part of a bigger project by Natural England which is also looking at the small pearl-bordered fritillary butterfly.

And as for Reid, a five-year-old Springer Spaniel who was raised to this role, he couldn't be happier.

This is his dream job; said Ms Cripps of RM Conservation, he would do it every day.

"I have to tell him when it's time to stop, he would just keep going," she said.

"Conservation detection dogs are another tool that can help fill a gap. They can detect in really low densities, because they use smell rather than sight.

"It's lovely to be a part of this," she added.

"Water voles are our fastest declining mammal. It's really important to have a better understanding, so we can better protect them.

"And it's never just one species really.

"You protect a habitat for one animal, and the chances are you are doing good on a much broader scale."

The water vole is often informally called the water rat, though it only superficially resembles a true rat. Water voles have rounder noses than rats, deep brown fur, chubby faces and short fuzzy ears; unlike rats their tails, paws and ears are covered with hair.