Dispersal patterns in black howler monkeys (Alouatta pigra): Integrating multi-year demographic and molecular data

Dispersal is a fundamental process in the functioning of animal societies
as it regulates the degree to which closely related individuals are
spatially concentrated. A species’ dispersal pattern can be complex as it
emerges from individuals’ decisions shaped by the cost-benefit tradeoffs
associated with either remaining in the natal group or dispersing. Given
the potential complexity, combining long-term demographic information with
molecular data can provide important insights into dispersal patterns of a
species. Based on a 15-year study that integrates multi-year demographic
data on six groups with longitudinal and cross-sectional genetic sampling
of 20 groups (N=169 individuals, N=21 polymorphic microsatellite loci), we
describe the various dispersal strategies of male and female black howler
monkeys (Alouatta pigra) inhabiting Palenque National Park, Mexico.
Genetically confirmed dispersal events (N=21 of 59 males; N=6 of 65
females), together with spatial autocorrelation analyses revealed that the
dispersal pattern of black howlers is bisexual with strong sex-biases in
both dispersal rate (males disperse more often than females) and dispersal
distance (females disperse farther than males). Observational and genetic
data confirm that both males and females can successfully immigrate into
established groups, as well as form new groups with other dispersing
individuals. Additionally, both males and females may disperse singly, as
well as in pairs, and both may also disperse secondarily. Overall, our
findings suggest multiple dispersal trajectories for black howler males
and females, and longer multi-year studies are needed to unravel which
demographic, ecological, and social factors underlie individuals’
decisions about whether to disperse and which dispersal options to take.