Barred buttonquail males outlive females

Sex differences in lifespan can vary considerably across species. Variance in lifespan depends on the progression of the mortality rate with age. Males are usually thought to have a shorter lifespan than females, which can be explained by sexual selection acting on secondary sexual traits that affect longevity. Such a bias in mortality between the sexes is also an indicator of the adult sex ratio. While there is evidence for this relationship from species with traditional sex-roles, little is known about the sex difference in lifespan of species that exhibit a reversal of sex-roles. Here we investigated sex differences in longevity and hatchling sex ratio in a captive population of barred buttonquails (Turnix suscitator), a sex-role reversed species with a classical polyandrous mating system. We found that males lived on average 1.7 times longer than females. Further, sex ratio at hatching did not divert significantly from parity. Our data suggest that in sex-role reversed species selective forces act on females leading to a shorter lifespan.

Methods
Data were collected over a period of 14 years on lifespan in male and female barred buttonquails, a polyandrous bird species that is rarely kept in captivity.