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Male migration in crested macaques (Macaca nigra): Challenges and consequences

Pascal Marty, PhD student, German Primate Center, Germany - completed 2014

The aim of this study is to better understand the implications of male migration on the males LRS in multi-male multi-female groups. We will test the knowledge of possible emigrants on the group composition, individuals and hierarchy of neighbouring groups, analyse the factors leading to a successful migration of a male and determine the long-term reproductive consequences of these migrations.

Project hypothesis:

Physiological preconditions of migrating males and their impact on the outcome of a migration

  • Immigrating males face different resistance from the resident males depending on their physical attributes and aggressiveness
  • Migrating males show different trends in the development of their hormone levels after a migration

P: Males that face a lower rate off aggression from the resident males show a lower increase in glucocorticoid and androgen levels

 

Within group social constellations and their influence on the number of immigration attempts

 

  • Potential emigrant males are aware of the male cohort in the neighbouring groups and their hierarchy

P: Males will identify individuals according to their acoustic and visual attributes

  • Migrations are more likely to occur when the resident males´ hierarchy is instable

P: More males immigrate into groups with a favourable male cohort

  • Males from a common natal group are more likely to be found in the same group as adults

P: Related males are found more often in the same group than expected by chance

Female Influence on the outcome of a migration

  • Social interactions with females favour integration

P: There is a negative relationship between the social affiliation rate with females and the rate of aggression received from resident males

Reproductive success of migrating males

  • Males who stay in a group for a longer time have a higher relative reproductive success than males who change the group often

P: Males who are not able to sire offspring emigrate

For this study we will work on the crested macaques (Macaca nigra) as an excellent study species to address migration related questions. This species shows an extraordinary high rate of migration whereby males often change groups several times in their lives. Nevertheless, a lot of migrations are not successful and the males leave the group after a short time. This macaque species exhibit the predominant social system within the primates (multi-male/multi-female groups) but may also be representative for other taxa. The dominant males do monopolise almost all copulations with fertile females, the hierarchical positions within the males change often and the within group male competition is high. 

The results of this study will help to understand the proximate and ultimate factors influencing the success and failure of male migration in multi-male primate groups. Furthermore, considering the strong impact of male migration on male LRS, our study will contribute to a better understanding of the evolution of social systems in primates.