An ultra-high frequency identification tag (10, 100) for attachment to an animal, said identification tag comprising: a body (12, 14, 112, 114); an integrated circuit; and, an ultra-high frequency antenna device electrically connected to said integrated circuit; wherein the antenna device comprises: a meander line antenna; and a substrate; wherein said antenna device is configured to use a body of the animal to which it is attached as part of a tuning circuit formed by the identification tag and the animal such that said antenna device fuses the body of the animal as a ground plane; and wherein said antenna device is configured to be purposely detuned such that it is only tuned to a desired frequency when the tag is attached to the animal; and wherein said meander line antenna is a three-dimensional meander line antenna comprising dimensions, antenna elements (220, 230), a spacing between said antenna elements, a number of turns; wherein said substrate comprises two layers, a spacing between said layers and a thickness; and wherein one or more of: the dimensions of the meander line antenna, the spacing between the elements (220, 230) and the layers of the meander line antenna, the number of turns of the meander line antenna; and the substrate thickness, is configured to impedance match the antenna device to said integrated circuit to which it is attached, and such that no further external impedance matching components are required. a body (12, 14, 112, 114); an integrated circuit; and, an ultra-high frequency antenna device electrically connected to said integrated circuit; wherein the antenna device comprises: a meander line antenna; and a substrate; a meander line antenna; and a substrate; wherein said antenna device is configured to use a body of the animal to which it is attached as part of a tuning circuit formed by the identification tag and the animal such that said antenna device fuses the body of the animal as a ground plane; and wherein said antenna device is configured to be purposely detuned such that it is only tuned to a desired frequency when the tag is attached to the animal; and wherein said meander line antenna is a three-dimensional meander line antenna comprising dimensions, antenna elements (220, 230), a spacing between said antenna elements, a number of turns; wherein said substrate comprises two layers, a spacing between said layers and a thickness; and wherein one or more of: the dimensions of the meander line antenna, the spacing between the elements (220, 230) and the layers of the meander line antenna, the number of turns of the meander line antenna; and the substrate thickness, is configured to impedance match the antenna device to said integrated circuit to which it is attached, and such that no further external impedance matching components are required. the dimensions of the meander line antenna, the spacing between the elements (220, 230) and the layers of the meander line antenna, the number of turns of the meander line antenna; and the substrate thickness, is configured to impedance match the antenna device to said integrated circuit to which it is attached, and such that no further external impedance matching components are required.