The ability to recognize oneself in a mirror is an exceedingly rare capacity in the animal kingdom. To date, only humans and great apes have shown convincing evidence of mirror self-recognition. Two dolphins were exposed to reflective surfaces, and both demonstrated responses consistent with the use of the mirror to investigate marked parts of the body. This ability to use a mirror to inspect parts of the body is a striking example of evolutionary convergence with great apes and humans.
Reiss, D., & Marino, L. (2001). Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence. Proceedings of the National Academy of Sciences, 98(10), 5937-5942.