Abstract:
For highly social species, population dynamics depend on
hierarchical demography that links local processes, group dynamics,
and population growth. Here, we describe a stage-structured matrix
model of hierarchical demography, which provides a framework for understanding
social influences on population change. Our approach
accounts for dispersal and affords insight into population dynamics at
multiple scales. The method has close parallels to integral projection
models but focuses on a discrete characteristic (group size). Using detailed
long-term records for meerkats (Suricata suricatta), we apply
our model to explore patterns of local density dependence and implications
of group size for group and population growth. Taking into account
dispersers, the model predicts a per capita growth rate for social
groups that declines with group size. It predicts that larger social groups
should produce a greater number of new breeding groups; thus, dominant
breeding females (responsible for most reproduction) are likely to
be more productive in larger groups. Considering the potential for future
population growth, larger groups have the highest reproductive value,
but per capita reproductive value is maximized for individuals in smaller
groups. Across a plausible range of dispersal conditions, meerkats’ longrun
population growth rate is maximized when individuals form groups
of intermediate size.
