This is a Degu. It is a native of Chile. Untamed degus, as with most small animals, can be prone to biting, but their intelligence makes them easy to tame.
i.e. more cuddly than your average brown rat!
Photographed on 15th May 2011 in Tilgate Park Nature Centre, West Sussex, England.
Camera Details: Nikon D7000, 18-200mm VR lens at 200 mm, 1/150s, f/5.6, iso 400, raw. Software Capture NX2