Females often live longer than men -- this is true for humans and for many other animal species.
The phenomenon exists even when you adjust for male risky behavior which leads to more early male deaths than female (car accidents, wars, homocides, etc).
Scientists don't know why. Females are not better at withstanding certain viruses or bacteria for instance -- there seems to be no obvious physiological reasons.
More robust females
A new study in Journal of Ecology has looked at sex differences and mortality in the Eurasian sparrowhawk. It turns out that heterogeneity is what drives longer lives in female sparrowhawks.
Heterogeneity in this context means that female sparrowhawk physiology is more diverse and less average than the males. There are more frail females than frail males, but there are also more robust females than robust males.
Surprised researchers
With more frail females, there will of course be more early female deaths than male. But this is more than weighed up by the larger number of robust females than males.
According to the study, the life expectancy for the most robust adult females reach up to 4.23 years, while for the most robust adult males it was 2.68 years.
The results are a surprise to the researchers.
Possible in other species.
It is possible that this phenomenon can be found in other animal species, but it is still uncertain. I suggest that when studying sex differences in mortality, researchers should consider accounting for heterogeneity.
The study also concludes
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Journal of Animal Ecology : Individual heterogeneity determines sex differences in mortality in a monogamous bird with reversed sexual dimorphism. Authors: Fernando Colchero, Alix Eva Aliaga, Owen Jones, Dalia Amor Conde.
Contact: Fernando Colchero, Associate Professor, PhD. Department of Mathematics and Computer Science and Max-Planck Odense Center. Email: olchero@imada.sdu.dk . Tel: +45 65502324. http://www.colchero.com
Journal of Ecology