Abstract
Abstract1. The conditions under which firemouth cichlids (Cichlasoma meeki) employed a branchiostegal display (erection of the gill membranes) were investigated to test four predictions concerning Increased Apparent Size (IAS) displays, in which the apparent size of an animal increases without an increase in Resource Holding Potential (RHP). Since size correlates with RHP for many species, IAS displays are assumed to increase an animal's apparent RHP. If contests are settled on the basis of differences in perceived RHP values, animals exhibiting falsely high values of RHP may avoid escalated contests and thus acquire resources at less cost. 2. The branchiostegal display could be performed alone or simultaneously with any other agonistic behaviour. It accompanied non-contact behaviour acts more commonly than contact acts, but accompanied no type of act more than one third of the times that act was performed. 3. It was performed primarily towards paired intruders, and those equal to or larger in size than the resident. 4. It was performed more often towards larger heterospecifics than towards larger conspecifics, and rarely towards smaller fish of any species. 5. The display often accompanied the first act of a contest, and this probability was greatest for contests with larger pairs of conspecifics. 6. The function of the display seems most likely to be a combination of an IAS display and a signal of a low probability of attack.
Published Version
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