Male cichlids â€˜shout' at each other during fights to prevent the situation from escalating, according to research by French biologists published in a recent issue of the journal Ethology.
A number of cichlids are known to produce sounds, either when two males spar with each other, or during courtship and breeding. Frédéric Bertucci and co-authors examined the role of sounds produced when two male Metriaclima zebra interact aggressively in their study.
The authors first placed two male cichlids in adjacent aquariums in which loudspeakers and hydrophones (underwater microphones) had been placed. The tanks were separated by an opaque partition.In the visual treatment, the opaque partition separating the two aquariums was removed, the loudspeakers were switched off, and the two fish were allowed to interact visually for 20 minutes.
In the acoustic treatment, the opaque partition remained between the aquariums and a 20-minute sequence of sounds produced by a resident male was played back to both fish simultaneously.
For the visual and acoustic treatment, the opaque partition was removed and the treatment period was divided into two sub-periods of 10 minutes, during which one fish could see and simultaneously hear its opponent (live condition), while the second fish could only see its opponent but was challenged with playback of recorded aggressive sounds whenever aggressive sounds were produced by the first fish (simulated condition).
The authors found that the male fish were visually, but not acoustically challenged to fight, i.e. the cichlids began to display aggressive behaviours when they could see their potential opponents, but not when they could only hear them. However, combining sound with visual stimuli lowered the level of aggression in the fishes, with the highest level of aggressiveness found when fishes were acoustically isolated and could only interact visually.
The authors hypothesise that the association of sound with other behavioural features suggests that the number of sounds produced and their acoustic characteristics may be used during a dispute to assess an individual’s status and/or motivation and may consequently modulate the opponent’s behaviour, resulting, in the present case, in a reduction in its aggressiveness.
This might avoid escalating interactions and one would expect the future winner of a fight to produce more sounds than the future loser.
This appeared to be supported by the data obtained from the experiment.
For more information, see the paper: Bertucci, F, M Beauchaud, J Attia and N Mathevon (2010) Sounds modulate males’ aggressiveness in a cichlid fish. Ethology 116, pp. 1179–1188.