The first time children can recognize themselves in a mirror is a significant developmental milestone. However, a new study has found that young bottlenose dolphins reach this stage sooner than human infants.
Human babies typically develop self-awareness, or the ability to recognize that the reflection in a mirror is themselves and not just another baby, around 12–18 months. In contrast, according to a study published this month in PLOS One, bottlenose dolphins (Tursiops truncatus) gain this awareness around seven months.
In the study, scientists at the National Aquarium in Baltimore watched two young bottlenose dolphins — a male and a female — over the course of three years, specifically examining how they interacted with their images in a mirror.
The female dolphin, named Bayley, showed social behaviors toward the mirror, such as “close-eye viewing, bubble production and body tilting,” beginning at seven months of age. The male, named Foster, was 14.5 months old when first introduced to the mirror, but he immediately exhibited the same behaviors as Bayley.
“Both dolphins produced a rich suite of self-directed behaviors at the mirror,” the study authors wrote. “Many of these were combinations of multiple behaviors, such as open mouth viewing and vertical head movements all while inverted. On several occasions, they also produced instances of what appeared to be ‘apparent social behavior,’ and other creative bubble production and play behaviors.”
One of the study authors, Diana Reiss of City University of New York’s Hunter College, had previously discovered dolphins can recognize themselves in a mirror (the results were published in The Dolphin the Mirror in 2011), but this was the first developmental analysis on very young dolphins.
The results “add new layers to our understanding of factors that may contribute to the capacity for [mirror self-recognition] across species and the evolution of intelligence in the animal world,” Reiss said in a press release from Hunter College.