SASEBO, Nagasaki Pref. (Kyodo) Researchers are conducting what may be the first experiment of its kind to determine the extent to which dolphins use their vision to tell their fellow sea mammals apart.
The researchers from the Umikirara Aquarium on Kujuku Island in Sasebo, Nagasaki Prefecture, and from Tokiwa University in Ibaraki Prefecture, have been testing dolphins' visual capacity by following their eye movements when they encounter footage of dolphins and killer whales on a large TV screen through the glass barrier of an aquarium.
The team has enlisted two female bottlenose dolphins at the aquarium, Nami and Niha, for the experiment. When the screen shows images of dolphins for a few seconds, the two move their heads slowly as if to ask "who are you?"
The researchers have been recording their eye movements with video to analyze patterns and duration to see how the dolphins are possibly recognizing the images using their eyesight.
Dolphins have been known to identify their surrounding environment by emitting ultrasound. There have been few studies into how much they use their vision, according to the researchers.
Fumio Nakahara, an associate professor at the university's college of community development, said dolphins could be visually distinguishing their fellow sea mammals by recognizing details.
"If we could find this out, we would be able to understand more about dolphins' social lives and gain clues about their evolution," Nakahara said.
