When the animal received a mark on its body visible only with the assistance of the mirror, it failed to notice or touch the mark.

WSJ: The Brains of the Animal Kingdom

Happy used her reflection to repeatedly touch the white mark with her trunk, which showed that she, at least, recognised her own reflection.

ECONOMIST: Self-recognition

It fell apart then, exploding in sparks, but she remembered how elated she felt to touch the scorch-mark and smell the hot, tarry smell of the destroyed wood.

ECONOMIST: Yelena Bonner