I wonder how one dissociates the cause and effect in animal studies. Healthier animals are more likely apriori to advance up the social hierarchy.

Nonetheless, it does make sense that social mammals could employ different strategies based on social rank. If you are at the top, you have more access to food and mates and a higher benefit to longevity. If you are at the bottom and have zero access to mates, longevity doesn't help your genes much, and your genes have an incentive to employ riskier strategies that could sacrifice longevity.