They've had films made.. and books written about them - and they are one of our most popular riverside mammals. The Otter was facing extinction in Britain several decades ago, but it is now having a resurgence - with a little helping hand from ecology experts.
They have now appealed for volunteers to help build a series of Otter holts - or dens - starting with one on the banks of the River Trent near Gainsborough in Lincolnshire. David Hirst reports.
Deer, foxes, otters and rare birds all live at Top Hill Low nature reserve near Driffield, but until now you'd have to be very lucky to see any of them.
The creatures, who go into hiding as soon as humans are on the scene, have been captured for the first time by new movement trigger cameras installed at the site. Victoria Whittam reports.
Following the success of a first camera to catch wildlife in action at Tophill Low nature reserve in East Yorkshire a second camera is being installed.
The first camera, put in by Yorkshire Water, shows a family of otters at play.