Being bigger or more colourful isn't all that a female guppy (Poecilia reticulata) looks for in a male — having the smarts is also important, according to research published in a recent issue of the Journal of Fish Biology.
The study, by Adam Shohet and Penelope Watt found that male guppies that learned faster were more desirable to females.
The authors first tested the learning ability of 27 sexually mature male guppies using two specially designed mazes.
In each run, a bloodworm was placed in the goal zone, the male guppy was placed in the start zone, and the amount of time that the guppy took to reach the goal zone was recorded.
Each male's attractiveness to females was then measured using a choice chamber, in which the female was placed in the central compartment and two males placed at each of the end compartments.
The position of the female was noted every 15 seconds for 10 minutes, and the number of times a female was found next to either male was counted for each trial. Each male was then awarded an attractiveness score.
The authors found that the female fish were more attracted to males that had learned the mazes faster. The females could not see the males learning the task, so they appeared to use a trait that predicts or correlates with a male's learning rate in their mate choice.
One possibility is that the females were selecting for bolder males, which may be more likely to complete the maze faster. Another explanation why females may prefer males with a faster rate of learning may be because these males are also more dominant.
Learning ability has been found to be related to dominance in guppies. The authors conclude that although female guppies seemed to prefer males with a faster rate of learning, the cue or cues they use remains unknown and further work is necessary to establish what these cues are.
For more information, see the paper: Shohet, AJ and PJ Watt (2009) Female guppies Poecilia reticulata prefer males that can learn fast. Journal of Fish Biology 75, pp. 1323–1330.