Which animal was the first non-primate to pass the mirror test?

The bottlenose dolphin was the first non-primate reported to pass the mirror test. In the test, researchers place a temporary mark somewhere the animal cannot normally see, then observe whether it uses a mirror to inspect that mark on its own body.

In a landmark study published in 2001, researchers Diana Reiss and Lori Marino tested bottlenose dolphins and reported behaviors consistent with mirror self-recognition. The dolphins approached the mirror quickly, made repeated head movements, and closely examined marked areas such as the eye or genital region. These actions differed from simply treating the reflection as another animal.

The result was important because mirror self-recognition had previously been most strongly associated with great apes. It is not, however, a complete test of intelligence or self-awareness. Animals that rely heavily on smell, touch, or other senses may fail a visual mark test without lacking self-awareness. Killer whales and some other species have also shown suggestive mirror behavior, but the bottlenose dolphin remains the canonical answer to this question.