Sex differences in the function of pair bonding in the monogamous convict cichlid

Many monogamous animals engage in a period of pair bonding prior to their ultimate mate choice (reproduction). One hypothesis about the function of this behaviour is that it allows individuals to continuously assess the quality of their partner as well as other potential mates. I tested this hypothesis in the convict cichlid, Amatitlania nigrofasciata, by providing males and females with a choice between their partner and a novel individual of the opposite sex at various time points after formation of a pair bond. Sex differences were observed in patterns of behaviour, with females significantly more likely to spend time with their partner than with another male, while males generally spent more time with a novel female than with their partner. The time spent in a pair bond affected this pattern, however, with both sexes showing a decreased time-based partner preference as the time in a pair bond increased. After forming a pair bond, males were largely aggressive towards novel females, treating them as territorial intruders, while pair-bonded females generally ignored novel males. Neither sex appeared to actively court potential mates apart from their partner. In a second experiment, I attempted to alter this pattern by presenting pair-bonded individuals with novel potential mates of relatively higher quality (larger size) than their partner. When given a ‘better option’, neither females nor males showed a preference for their partner over a large novel mate. All males continued to treat novel females as territorial intruders, while a subset of females shifted their preference from their partner to a larger novel male. These results support the hypothesis that the role of pair bonding may differ between the sexes in this species, functioning as a prolonged period of mate assessment in females, but not in males.