The
number of males found within a group has important consequences for a
group’s social dynamics, and is one of the most flexible features of
group-living across and within species. Blue monkey groups consist of
multiple females and a ‘resident’ male. ‘Influx’ males may join
groups – typically during mating seasons – and remain well beyond the
mating season. Using nine recent years of data from multiple groups
that varied in size, I described variation in the number of males per
group on a daily basis and over time. To describe the variation among
groups not captured in the population-wide mating seasons, I calculated
group-specific conceptive periods based on infant birthdates. I
used generalized linear mixed models to assess the relationship between
the number of adult males and the number of sexually active females
during the population mating season and during group-specific
conceptive periods. To examine the directionality of this
relationship, I used a cross-correlation analysis with lags of 1-5
days. I used generalized estimating equations to explore whether
group size related to the presence of multiple males or synchrony of
sexual behavior. These analyses revealed that, with a larger data set
and greater variety of groups, the distinction between influx and
non-influx mating seasons was less clear-cut than previously reported.
Female sexual activity predicted male numbers during both mating
seasons and conceptive periods, with a stronger effect in conceptive
periods. In addition, larger groups were more likely to contain
multiple sexually active females, as well as multiple males.
Correlations between the numbers of sexually active females and number
of males were strongest when these variables were measured on the same
day, though significant correlations occurred when measurements of one
variable preceded or followed the other by approximately 1-5 days. Rank
dynamics of males did not appear to predict the number of males that
co-occurred in a group.After graduation, Lu worked for the Rainforest Alliance and then the World Wildlife Fund (TRAFFIC).
Publication based on MA thesis:
Gao, L. & Cords, M. 2020. Effects of female group size on the number of males in blue monkey (Cercopithecus mitis) groups. International Journal of Primatology. doi: 10.1007/s10764-020-00174-3