Abstract: The invention concerns an ear tag (1) for identifying animals, comprising at least a flexible planar wall (2) made of coloured aromatic polyurethane, on one of the large surfaces whereof is affixed a marking in the form of a sign and/or of alphanumeric character and/or of bar code. To prevent degradation by external agents one of the large surfaces at least of the planar wall (2) is coated with a layer of protective material (3) forming for example a screen against UV radiation and a barrier against chemical attacks of certain corrosive agents present in the environment. Said protective layer is made of aliphatic polyurethane.