In 2008, after sightings of otters at Attenborough Nature Reserve, a holt was constructed on one of its islands. Tim Sexton, Assistant Manager, said: "Having otters is a really good indication of the quality of the reserve."
October 2010 and it was time to head out on the Nottinghamshire Wildlife Trust boat to the island to check if the elusive mammals have moved in.
Tim Sexton helped build the holt. He said: "[Today] is the first time we've ever been on the island since building the artificial holt so it's going to be the first indication that they've used it."
Graham Bowden is a ranger at Attenborough. He said: "The only recent [otter] sighting we've had was in this area [near the holt], we've got good reason to believe they may be using it."
Graham added: "We need to try and find some mud on the shore [for footprints]. Or a log would be an ideal place to look for spraints [otter excrement]."
Graham's attention was drawn to depressions in the mud but, sadly, it was a false alarm. "Looking for tracks you see what you want to see," said Graham. "A depression caused by a rain drop could look like a toe and away you go."
This is what an otter footprint looks like. The picture was taken at Attenborough in April 2008 and shows the print next to a two pence piece.
The holt is now overgrown and to anyone other than the rangers you could not tell that, potentially, a family of otters could be inside. Tim said: "It's nice to see [the holt] after two years and see how well established it is and how it's blended in."
Graham could not find any evidence that otters were using the holt. "We're not going to be disheartened about it," said Tim. "Otters do have large territories, it could be that this is just a seasonal territory."
Fish skeletons and opened swan mussels were found. Tim said that otters would eat the mussels but are more likely to focus on eels and small fish. This fish could have been eaten by another predator, like a mink.
Tim found a small spraint underneath a bridge away from the holt. An otter spraint can smell like jasmine tea but he could not be 100% sure about the animal which made this one.
"There's more mammal bones than fish bones," said Tim. "There's bits of fur, certainly doesn't have that jasmine tea smell but they do smell a bit fishy."
Tim decided to take the spraint back to the centre for analysis. "It will keep me entertained for this afternoon!" said Tim.
Tim and Graham are sure that somewhere otters are living and hunting at Attenborough Nature Reserve but many of the sightings so far have turned out to be the non-native mink. Otters are much bigger and more elusive.
Attenborough Nature Reserve's rangers and other experts often run courses in mammal identification. Find out when and where by visiting the website: www.attenboroughnaturecentre.co.uk