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Living in nonbreeding groups: an alternative strategy for maturing gorillas
Florence Levréro1, Sylvain Gatti, Nelly Ménard
1Université Rennes 1, CNRS UMR 6552, Ethologie-Evolution-Ecologie, Station Biologique, Paimpont, France. florence.levrero@univ-rennes1.fr
American Journal of Primatology
|February 16, 2006
Summary
Young male gorillas form nonbreeding groups (NBGs) for protection and experience. These groups help aging silverbacks improve inclusive fitness and young silverbacks increase chances of forming future breeding groups (BGs).
Area of Science:
- Primate Behavior
- Conservation Biology
- Social Dynamics
Background:
- One-male reproductive strategies exclude maturing males from reproduction.
- Excluded male gorillas form solitary or nonbreeding groups (NBGs) without adult females.
- The social dynamics within NBGs remain poorly understood.
Purpose of the Study:
- To investigate the formation and dynamics of NBGs in western lowland gorillas (Gorilla gorilla gorilla).
- To analyze NBG composition based on age-sex classes, relatedness, and individual transfer patterns.
- To explore the potential benefits of NBG membership for individual gorillas.
Main Methods:
- Study conducted on a population of 377 gorillas at the Lokoué clearing in the Republic of Congo.
- Detailed observation of NBG formation and member dynamics.
- Analysis of age-sex classes, relatedness among members, and origins/destinations of transferring individuals.
Main Results:
- NBGs primarily comprised immature males, often migrating voluntarily from natal groups.
- Some individuals, including juvenile females, originated from disbanded breeding groups (BGs).
- Migrants favored NBGs with a silverback; dispersal was not solely relatedness-driven but favored association with related silverbacks.
Conclusions:
- NBG membership offers enhanced protection from predators and valuable environmental experience for young males.
- Aging silverbacks benefit through inclusive fitness by tolerating and protecting offspring within NBGs.
- Young, healthy silverbacks can improve their prospects of establishing future BGs by attracting females.
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