Saw this grass snake - Natrix natrix - in the Selva de Oza here in the Hecho Valley on July 1st 2008. It felt threatened when I took the photo and puffed itself up to look more menacing. Even though I know they are completely harmless I didn´t want to get too close!
Their scientific name Natrix natrix refers to their excellent swimming ability. Their main prey are frogs, other small reptiles and small fish. The valley here with its healthy river and mountain streams is an ideal habitat for them.