| Abstrakt: |
Group-living species are often organized into social dominance hierarchies, where high-ranking individuals have priority of access to resources, including estrous females. Traits associated with male dominance status should thus be correlated with reproductive success, but, with the exception of research on some primates, studies with both behavioral data to determine dominance hierarchies and a pedigree to identify male siring success are rare. For a wild population of sexually dimorphic eastern grey kangaroos Macropus giganteus, we characterized the social hierarchy over 6 non-consecutive years to investigate the relationship between male dominance and yearly reproductive success. Dominance hierarchies were steep, linear, and stable over time. Asymmetries in body mass and size between contestants were strong predictors of contest outcomes, and these morphological traits were positively correlated with dominance status. Males did not spatially avoid each other but tended to fight with individuals of similar size, suggesting that when asymmetries were large, contests were unlikely. Dominance status was under strong sexual selection, despite moderate monopolization of paternities by highly dominant males. Overall, these results suggest that body size and weapons are important determinants of dominance status and male reproductive success but that other traits play a considerable role. A clear-cut dominance hierarchy and strong selection on dominance status do not necessarily lead to monopolization of reproduction by the most dominant males in this strongly sexually dimorphic species. Significance statement: It is generally assumed that high social rank in males is a very strong determinant of access to mates in polygamous species. Like other sexually dimorphic species, male kangaroos are thought to establish dominance hierarchies based on size. A few high-ranking males are then believed to monopolize matings. Our study confirms a strong correlation between body size and dominance status, and that males mostly engage in contests with males of similar size. However, we also found weak monopolization of reproduction, despite strong, positive sexual selection on dominance status. This result suggests that strong selection for high rank does not imply that subordinate males cannot sire offspring. A few highly dominant males had high reproductive success but did not monopolize matings. [ABSTRACT FROM AUTHOR] |
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