When I first started to explore the canals round London 30 or more years ago sightings of water voles shaking themselves dry on the bank or the characteristic plop as they dived in to the water were really common.

We recognised them as the anti-hero of the delightful book The Wind in the Willows. We called him Ratty but in fact he was not a rat at all. He wasn’t really well designed for his aquatic life either. No webbed feet, fur that wasn’t waterproof and an inability to swim far under water.

What he was was a lovable water vole (Arvicola amphibious).

Many older field guides still listed him as Arvicola terrestris. Whatever we call him, sadly, Ratty is now one of the most seriously endangered mammal species in Britain today. 

In 1960 it is estimated there were around 8 million water voles. Now there are probably only about a third of a million and that incredible decline goes on.  

Unsympathetic farming and watercourse management which destroyed parts of the water vole’s habitat have been major factors in the animal’s problems.

Another key factor is predation by American mink. Mink were introduced for the fur trade but frequent escapes and some rather unwise, if well intentioned, direct action by animal rights activists who liberated huge numbers of mink from fur farms upset the natural food chain balance on Britain’s waterways.

Mink are now a common pest. 

Water voles find it harder and harder to survive. Other vole predators include otters, stoats, weasels, brown rats, domestic and feral cats, pike, herons and barn owls. Poor Ratty it seems has lots of enemies.  

Water voles are still found throughout England, Wales and Scotland, though their distribution is patchy.

They live in burrows excavated within the banks of rivers, canals, ditches, ponds and streams. Burrows are normally located adjacent to slow moving, calm water. They can also live in reed beds where they will weave ball-shaped nests above ground if no suitable banks exist in which to burrow.

The voles feed close to these holes or nests, mowing conspicuous closely cropped lawns around them. 

They can be recognised by rounder noses than rats, deep-brown fur, chubby faces and short fuzzy ears — unlike actual rats their tails, paws and ears are covered with fur.

In the wild, on average, water voles only live about five months. They reach up to 210 mm (8.5in) including a tail of 60 mm (2.5in). Adults weigh up to 350 grams (12oz) but many are considerably smaller. 

Water voles mainly eat grass and plants near the water. At times, they will also consume fruits, bulbs, twigs, buds and roots. 

Recent studies have discovered that the normally vegetarian water voles are under such stress that in some locations they have started attacking frogs, often eating legs and discarding the body.  

They mate from March into late autumn. Pregnancy lasts 21 days, after which up to eight young can be born. The young voles open their eyes three days after their birth. 

Water voles are expert swimmers and divers. They do not usually live in large groups. Adult water voles each have their own territories, which they mark with droppings. 

In April 2008 the British government announced full legal protection for water voles and now the Canals and Rivers Trust — the charity the Con-Dem government cobbled together to privatise Britain’s waterways by the back door — has launched a financial appeal to fund their work trying to restore water vole habitat.

Both the law and the begging bowl are too little too late. 

The water vole’s parlous state is just one more example of the betrayal of David Cameron and Nick Clegg’s promise to be the greenest government ever.

The real rats it seems are not to be found down by the canal but in the Cabinet rooms of Westminster.