In the Ngorongoro Crater of Tanzania, spotted hyenas have been quietly teaching scientists a lesson about the messy complexity of power. For 28 years, researchers from the Leibniz Institute for Zoo and Wildlife Research have watched 481 hyenas navigate their tightly ranked clans, and what they've discovered challenges the way we measure dominance itself. The finding, published in Ecology and Evolution, reveals that a hyena's position in the hierarchy doesn't work the same way for every aspect of life—and that matters deeply for understanding how society shapes survival.
The insight sounds simple at first: dominant hyenas breed more successfully. But the research team, led by Ella White at Leibniz-IZW's Ngorongoro and Serengeti Hyena Projects, found that this straightforward assumption collapses under scrutiny. The problem isn't the observation—it's how we measure rank itself. Scientists have long used two distinct methods to calculate where an animal sits in the social order, and the team's question was direct: which method actually predicts reproductive success?
The first method, called "ordinal rank," treats hierarchy like a simple ladder. The dominant animal gets rank 1, the next gets rank 2, and so on down to the lowest-ranking member—a number equal to the total clan size. This metric captures absolute position: how many other animals have priority access to food and mates ahead of you. The second method, "standardized rank," normalizes this position by dividing by group size. A hyena ranked highest becomes 1, the lowest becomes -1, and the ratio reflects what proportion of the clan stands above versus below you.
When White and her colleagues tested these metrics against six different measures of reproductive success—offspring survival, birth intervals, age at first breeding for females, and offspring per year, mate rank, and age at first breeding for males—the answer wasn't uniform. For four traits, ordinal rank won out. For one critical trait in females, the interbirth interval, standardized rank proved superior. And for one trait, male age at first reproduction, neither metric reliably predicted anything at all.
The distinction matters biologically because it reveals how power operates differently across different challenges. Female spotted hyenas face an energy crisis: pregnancy, lactation, and nursing drain resources at extraordinary rates. What matters most for them is the absolute number of competitors between them and the food source. A female ranked fifth in a clan of ten faces a different reality than a female ranked fifth in a clan of thirty. Ordinal rank captures this cruel arithmetic perfectly—fewer animals ahead means richer milk and healthier calves. But interbirth interval, the time between successive births, follows a different logic. Here, the proportion of subordinate animals matters more, possibly because females calibrate reproduction based on the overall stability and resources of the group around them.
The researchers' work carries a message beyond the Ngorongoro Crater. In an era when scientists study hierarchy across species—from primates to dolphins to wolves—this work suggests we've been using one-size-fits-all measures to describe fundamentally nuanced systems. Understanding not just who wins conflicts, but how different forms of dominance ripple through different aspects of life, opens a richer picture of how animal societies really work. For the spotted hyenas of Tanzania, it means that rank is not one thing, but many things at once—and only by naming them separately can we truly understand what power means.