They are one of Britain's most elusive mammals.

But now, otters are making a comeback in Hull.

The creatures have been spotted in the city for the first time in more than thirty years.

Otters came close to extinction in Britain in the second half of the 20th century after pesticides used in farming contaminated their food.

They also suffered from loss of habitat as many wetlands were drained for farming.

Over the past ten years, officers at the Yorkshire Wildlife Trust (YWT) have been working with landowners along the River Hull valley from Driffield to Hull to try to encourage otter re-colonisation.

And the furry water-loving creatures have now been spotted for the first time in Hull since the 1970s, hundreds of yards from people's homes.

The first otter was seen on the River Hull in Kingswood and a second was reported on the Holderness Drain between Longhill Loglands and Bransholme Lakes.

Both were spotted by members of wildlife and conservation groups.

Otter footprints and droppings have now also been found within the city boundaries.

Jon Traill, conservation project manager at YWT who runs the River Hull Project, said: "It is amazing to think that in a busy city, with all those people around, one of the UK's most elusive mammals is hanging around, probably within a few yards of people.

"To have these live sightings is really good news."

The otter population had, until recently, been held back by the lack of available undisturbed spaces for them to inhabit in and around the city.

So the YWT team has worked hard to enhance river and wetland habitats for otters and other wildlife within the river catchment.

The team picks unused patches of land and improves them as habitats by planting more cover or building artificial 'holts' - holes in the ground where otters nest.

Hull may seem like an unlikely destination for such rare animals but, according to Mr Traill, the city is a good location for otters.

Its many interlinking waterways provide a good network through which they can travel, hunt and explore.

Mr Traill said: "Hull is actually quite a good habitat for otters.

"Hull is pretty good in terms of empty green areas and it has the continuity of the water system with the river and big drains like Holderness and Barmston and Fordyke Stream at the top of the city and the smaller dykes and ditches which otters would investigate.

"There is farmland right up to the edge of the city and there are a lot of brownfield old industrial sites within the city which have patches of unused land by the river which have grown up and would provide good cover for an otter.

"Old industrial units can be really good for otters."

Otters have been seen on the River Humber in recent years so there was a suspicion they must be travelling through Hull but officers at YWT were unable to find any evidence of them.

Mr Traill said: "The River Hull itself never completely lost all its otters but the numbers were very, very low.

"There were probably only a couple of the animals left on the River.

"In the 1980s and 90s we found signs that there were otters in the northern part of the river around Driffield.

"We had a suspicion that they were using the city as they had been seen on the River Humber so it would make sense for them to be using the River Hull and the drains.

"But finding any signs and proving they were doing that was very difficult."