Dominance, fatness and fitness in female American bison, Bison bison

Abstract

In females of several mammalian species, it is becoming evident that benefits related to high dominance rank can result in increased fitness, albeit to a lesser degree than in males. We examined indicators of fitness in relation to dominance rank in a group of adult female American bison in semifree-ranging conditions. A significantly linear dominance hierarchy was found. Dominance rank correlated significantly with three indicators of body condition: weight, speed of hair loss and fatness. After statistical correction for the other two factors, only the link between rank and fatness remained significant. Dominant females did not show higher fecundity, nor did their daughters. Combining the results over the study years, we found that weight of offspring at weaning correlated significantly with maternal rank.