British and Jamaican scientists recently released a study showing how Trinidadian guppy fish change their eye colors to initiate confrontations. Study authors believe their work will help biologists better understand the evolution and competitive dynamics of certain tropical fish.
For this study, researchers first observed the irises of large Trinidadian guppies as robotic replicas of smaller guppies swam towards them. Investigators instantly noted that these larger guppies changed their iris color from neutral silver to black when they were about to start a confrontation.
When researchers observed smaller guppies, however, they discovered that they did not change their eye color when presented with a potential threat. Scientists believe this is because smaller guppies know they wouldn’t be able to survive a confrontation as the larger guppies do.
Interestingly, larger guppies were more prone to attack smaller robotic guppies with black rather than grey eyes. This finding suggests that smaller guppies keep their eyes grey to avoid confrontations with larger fish.
Although guppies originated in northeastern South America, they are now one of the world’s most common tropical fish. Because of their wide diffusion around the world, scientists often use guppies in various tests on evolution and animal behavior.
The two major universities involved in this study were the UK’s University of Exeter and Jamaica’s University of the West Indies. Dr. Robert Heathcote, who teaches animal behavior at the University of Exeter, was this study’s lead author. A few other key researchers involved in this project include Drs. Jolyon Troscianko, Michael R.M. Lawson, and Antony M. Brown.
Anyone interested in this study should pick up the latest copy of Current Biology. Professors entitled their research, “Dynamic eye colour as an honest signal of aggression.”