Flocks of domestic geese synchronise egg laying in the same way that women's menstrual cycles can come into sync, according to new research.
Psychologist John Kent and colleagues at University College, Dublin, found that during the laying season the egg production of individual geese within a flock coincided with that of other members of the flock.
According to the study, this phenomenon is regulated by social factors specific to the flock and not by seasonal or weather patterns known to facilitate synchronised breeding in species such as sheep and deer.
Dr Kent said that the study strongly suggested that the causal mechanisms of menstrual synchrony in women and the effect seen in geese are similar.
He told The THES: "Our study supports evidence for the convergence of menstrual cycles in women, which is thought to be regulated by social interaction."
The researchers observed the effect in eight separate flocks of geese that made up the total population on a farm. Each of these flocks formed distinct social units and were housed separately but shared the same fields and farmyard.
The study states that the synchrony was not observed over the total population of geese because separate flocks did not synchronise with each other. This indicates a mechanism that works within flocks.
Scientists still hotly debate menstrual synchronisation despite a large body of evidence supporting its occurrence.
Jeffrey Shank of the department of psychology at the University of California said that menstrual synchrony observed in women was a byproduct of methodological errors and that this explanation could similarly apply to the effect seen in geese. He said: "Over a period of time, women's cycles are bound to converge by chance. People notice when this happens and take it as confirmation of menstrual synchrony."
These findings are published in the journal Applied Animal Behaviour Science.