Mammals live longer when they don’t reproduce

A large international study has discovered that contraception increases life expectancy in many species of mammals. 

Some animals live longer and reproduce only a few times, while others, such as mice, live for only a few years yet can reproduce hundreds of times.  

Researchers found that, on average, contraception extended animals' lifespans by 10% across species. While males benefit only when testosterone is removed by castration, females benefit from any form of reproductivesuppression, likely to avoid the high demands of pregnancy and lactation.  

The causes of death also differ by sex. Males die less from risk-taking behaviours and females die less from infections, supporting the idea that female reproduction weakens the immune system.   

The study combined the analysis of 71 previously published studies with records from 117 species living in zoos and aquariums worldwide.  

"Animals [in zoos] may receive contraception or sterilization to prevent breeding, creating natural comparison groups within the same environment," said Johanna Staerk, one of the authors of the study published in Nature and researcher at the Max Planck Institute for Evolutionary Anthropology, part of the EARA member Max Planck Society. 

However, evidence from humans is very scarce and based on centuries-old records that should be interpreted carefully. “Reproduction is inherently costly. However, human environments - through healthcare, nutritionand social support - can buffer or reshape these costs," caution the authors.