Female mammals live longer than males in the wild
A study focused on wild mammals has revealed that females have significantly longer lifespans than males. Among humans, women have a life expectancy that is nearly eight percent higher compared to men. The new research confirms that this statistic holds true for many other mammals as well.
The researchers analyzed the lifespans of 101 different species, including elephants and sheep. Among more than 60 percent of the mammal groups studied, females had a longer life expectancy by an average of 18 percent.
Study co-author Tamás Székely is a professor in the Milner Centre for Evolution at the University of Bath.
“We’ve known for a long time that women generally live longer than men, but were surprised to find that the differences in lifespan between the sexes was even more pronounced in wild mammals than in humans,” said Professor Székely. “This could be either because females are naturally able to live longer, or that female mortality drops compared with males.”
The study revealed that males do not age faster than females, but instead have a higher risk of mortality in adulthood. The researchers propose that lifespan is influenced by a combination of environmental factors and sex-specific variations.
“For example, lionesses live at least 50% longer in the wild than male lions. We previously thought this was mostly due to sexual selection – because males fight with each other to overtake a pride and thus have access to females. However, our data do not support this. Therefore there must be other, more complex factors at play,” explained Professor Székely.
“Female lions live together in a pride, where sisters, mothers and daughters hunt together and look after each other, whereas adult male lions often live alone or with their brother and therefore don’t have the same support network.”
“Another possible explanation for the sex difference is that female survival increases when males provide some or all of the parental care. This is also true in birds. Giving birth and caring for young becomes a significant health cost for females and so this cost is reduced if both parents work together to bring up their offspring.”
Next, the researchers will investigate the lifespans of captive zoo animals, who are not exposed to predators and do not have to compete for food or mates. The results will be compared to the data on wild mammals, which will help to clarify how much biological differences between the sexes may impact life expectancy.
“By affecting males and females differently, harsh environmental conditions such as a high prevalence in pathogens, is likely to cause sex-differences in lifespan,” said lead author Jean-François Lemaître. “Comparing the sex gap in lifespan and aging across several populations of the same species is definitely full of promises.”
The study is published in the Proceedings of the National Academy of Sciences.