Reproductive synchrony

Reproduction is said to be synchronised when fertile matings across a population are temporarily clustered, resulting in multiple conceptions (and consequent births) within a restricted time window.

On the other hand, theoretical models predict that group-living species will tend to synchronise wherever females can benefit by maximising the number of males offered chances of paternity, minimising reproductive skew.

[7] For example, the cichlid fish V. moorii spawns in the days leading up to each full moon (lunar synchrony),[8] and broods often exhibit multiple paternity.

[9] The same models predict that female primates, including evolving humans, will tend to synchronise wherever fitness benefits can be gained by securing access to multiple males.

[12] To any local group of females, the more such philandering can be successfully resisted—and the greater the proportion of previously excluded males who can be included in the breeding system and persuaded to invest effort—the better.

Figure a . Females competing for good genes should avoid ovulatory synchrony. Moving from one female to the next, a single dominant male under these conditions can exercise a monopoly. Key : Circle = female. Pointer = ovulation. Triangle = male.
Figure b . Females in need of male time and energy should synchronise their cycles, preventing any one male from monopolising access.