Female Mammals Outlive Males by 12% on Average

If you're a male mammal, you've drawn the short straw in the longevity lottery. Across nearly three-quarters of all mammal species, females outlive males by an average of 12 percent. That's the conclusion of a massive 2025 study that analyzed lifespan data from 528 mammal species—from elephants to bats to humans.

This isn't just about predators eating more males or human men taking more risks. The pattern persists even in zoos, where animals are protected from harsh weather, starvation, and getting chased by leopards. Something deeper is at play.

The Mating Game Costs Men Years

The biggest culprit? Sexual competition. In species where males compete intensely for mates—think elk battling with antlers or elephant seals fighting for beach territory—males die significantly younger. The energy spent on muscles, weapons, and testosterone-fueled brawls takes a toll.

Meanwhile, in the rare mammal species that practice monogamy, the lifespan gap shrinks dramatically. When males aren't constantly competing, they live almost as long as females.

Motherhood Is a Longevity Hack

Here's a twist: female mammals that invest heavily in parenting actually live longer, not shorter. Primate mothers, for instance, care for their young for years—and evolution has apparently rewarded that investment with extra lifespan. If you're going to spend a decade raising a kid, you'd better stick around long enough to see them through.

Males in species with involved fatherhood also see longevity benefits, though the effect is weaker.

Your Chromosomes May Be Sabotaging You

Sex chromosomes play a role too. In mammals, males have XY chromosomes while females have XX. That second X chromosome gives females a backup copy of critical genes—if one X has a mutation, the other can compensate. Males don't have that safety net.

Birds flip the script entirely. Female birds are the heterogametic sex (ZW chromosomes), and surprise—male birds live 5% longer on average. The chromosome disadvantage strikes again.

Humans Follow the Pattern

We're no exception. Women worldwide outlive men by 4-6 years on average. Some of that gap comes from behavioral differences—men take more physical risks and have higher rates of smoking and dangerous jobs—but even when researchers control for lifestyle factors, women still come out ahead.

The reasons echo across species:

• Testosterone increases cardiovascular strain and risk-taking behavior
• Women's second X chromosome provides genetic redundancy
• Estrogen offers some protective cardiovascular effects
• Men historically faced more violence and dangerous competition

So the next time someone suggests that women are the "weaker sex," point them to the lifespan data. Across the mammal kingdom, females are outlasting males by over a decade in many species—not despite the challenges of reproduction and parenting, but possibly because of them.