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Research on fighting has emphasized contests between individuals, typically males, but pairs also compete. Monogamous pairs of convict cichlids (Archocentrus nigrofasciatum) compete with other pairs for breeding sites in nature. We simulated such contests with competing pairs who differed in one or two of three possible asymmetries: body size, residency, and pair experience. In single-asymmetry experiments, larger pairs defeated smaller pairs, resident pairs defeated intruder pairs, and experienced pairs (those that had been together for 96 hours) defeated novice pairs (those that had been together for 48 hours). Thus, each of the three asymmetries was important in determining the outcome of contests. In further experiments, pairs had two contrasting asymmetries simultaneously. Larger pairs always defeated smaller pairs (15-25% difference in male standard length) even though the larger pair was inferior in one of the other asymmetries. When the two pairs were similar in size (standard length of males differed less than 6%), experienced intruder pairs defeated novice resident pairs nearly half the time. This is the first study to investigate the effects of pair experience on fighting ability. Although we predicted that experience might benefit pairs through improved coordination of their behaviour, behavioral measures such as time spent at the spawning site and pair digging behaviour showed no significant differences among groups. We posit that more experienced pairs fought harder for the breeding site because they were closer to spawning and the expected payoff for winning the breeding site was therefore higher. Finally, when both pairs were of similar size but differed in residence status and experience, there was more escalated fighting than in contests between size-disparate pairs; two possible interpretations of this result are discussed.

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In this experiment we examined the roles of male size and female eavesdropping in divorce using the serially monogamous convict cichlid (Archocentrus nigrofasciatus) by testing predictions based upon the better option hypothesis of divorce. We tested the role of male size by exposing females to males that were 20-25% larger than their current mate or males that were similar size to their current mate. Female convict cichlids prefer larger males, therefore we predicted that the frequency of divorce would be higher when the alternate mate was larger than the current mate. We also examined the role of eavesdropping as a mechanism of female assessment of relative male quality. Females were either permitted to eavesdrop (males physically interacted) or females were unable to eavesdrop (males prevented from interacting). We predicted that female eavesdropping would result in greater frequency of divorce. We found that females chose divorce most often (50% ending in divorce) in the treatment where the alternate male was larger than the current mate and eavesdropping was permitted, whereas females never chose divorce in the treatment where the alternate male was similar in size to the current mate and the female was not permitted to eavesdrop. Although it had a mild effect, male size difference alone did not significantly increase divorce. When size difference was coupled with eavesdropping, however, females did significantly increase their divorce rates.