A horse will apparently notice a mark on its face in the mirror
Baragli, P., Scopa, C., Maglieri, V. et al.
Horses seem to recognise themselves in mirrors, and they may even use the information in their reflection to recognise their face is dirty and needs wiping clean.
Eleven horses out of a group of 14 tested tried to rub coloured marks off their own cheeks after they discovered them in a mirror. This makes horses the only animals, besides primates, found to be generally capable of self-recognition in a mirror, says Paolo Baragli at the University of Pisa, in …
source: newscientist.com