Before squaring up for a fight, some fish check themselves out in the mirror to make sure they're big enough. This strange behavior was seen in bluestreak cleaner wrasse (Labroides dimidiatus), who ...

Bluestreak cleaner wrasse are small, territorial fish that aggressively fend off intruders. But when they have access to a mirror, the fish size themselves up before deciding whether or not to fight.

Before deciding whether or not to fight another fish, cleaner wrasse check their own reflection in a mirror and size themselves up. First, Taiga Kobayashi at Osaka Metropolitan University in Japan and ...

Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world. For decades, self-awareness has been guarded as a very ...