Data from: Complex sources of variance in female dominance rank in a nepotistic society

Many mammalian societies are structured by dominance hierarchies, and an
individual's position within this hierarchy can influence
reproduction, behaviour, physiology and health. In nepotistic hierarchies,
which are common in cercopithecine primates and also seen in spotted
hyaenas, Crocuta crocuta, adult daughters are expected to rank immediately
below their mother, and in reverse age order (a phenomenon known as
‘youngest ascendancy’). This pattern is well described, but few studies
have systematically examined the frequency or causes of departures from
the expected pattern. Using a longitudinal data set from a natural
population of yellow baboons, Papio cynocephalus, we measured the
influence of maternal kin, paternal kin and group size on female rank
positions at two life history milestones, menarche and first live birth.
At menarche, most females (73%) ranked adjacent to their family members
(i.e. the female held an ordinal rank in consecutive order with other
members of her maternal family); however, only 33% of females showed
youngest ascendancy within their matriline at menarche. By the time they
experienced their first live birth, many females had improved their
dominance rank: 78% ranked adjacent to their family members and 49% showed
youngest ascendancy within their matriline. The presence of mothers and
maternal sisters exerted a powerful influence on rank outcomes. However,
the presence of fathers, brothers and paternal siblings did not produce a
clear effect on female dominance rank in our analyses, perhaps because
females in our data set co-resided with variable numbers and types of
paternal and male relatives. Our results also raise the possibility that
female body size or competitive ability may influence dominance rank, even
in this classically nepotistic species. In total, our analyses reveal that
the predictors of dominance rank in nepotistic rank systems are much more
complex than previously thought.