Appearance affects aggression

Geophagus brasiliensis. Photo from

There are lots of variables that affect a cichlid’s aggression. Did you know that physical body colors is one of them? Some recent research using Pearl cichlids (Geophagus brasiliensis) as a model investigated how body coloring might affect territorial aggression levels.

Researchers studied the effects of body colors of G. brasiliensis intruders on resident (territory owner) conspecifics and vice versa. What they found was that body colors do influence the aggression levels of both resident AND intruder aggression. Subordinate color signaling fish induced greater aggression by defenders than by intruders.  This shouldn’t be expected to mean that body color is the only influential variable. There are lots of other factors – body size, behavior, hormone excretion, etc. The paper, published in Nature, is titled “Intruder traits modulate aggressive behavior of territory owners.”

Full Reference: Miyai, C.A., Sanches, F.H.C., Costa, T.M. et al. Intruder traits modulate aggressive behavior of territory owners. Sci Rep 10, 12050 (2020).


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