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Mountain gorilla ranging patterns: influence of group size and group dynamics
Damien Caillaud1, Felix Ndagijimana, Anthony J Giarrusso
1The Dian Fossey Gorilla Fund International, Atlanta, Georgia; Center for Geographic Information Systems, College of Architecture, Georgia Institute of Technology, Atlanta, Georgia.
American Journal of Primatology
|February 28, 2014
Summary
Mountain gorilla populations are growing, but increased overlap in home ranges leads to more frequent encounters. This suggests no current feeding competition, but higher risks of injury and infanticide for Virunga gorillas.
Area of Science:
- Primate Ecology
- Conservation Biology
- Behavioral Ecology
Background:
- The Virunga mountain gorilla population has nearly doubled since the 1980s, now comprising 480 individuals within a 430 km² protected area.
- Understanding ranging patterns is crucial for assessing food and space competition in growing gorilla populations.
Purpose of the Study:
- To analyze 12 years of ranging and encounter data for 11 Virunga mountain gorilla groups.
- To investigate the effects of population growth and group formation on home range size, overlap, and inter-group interactions.
Main Methods:
- Utilized 12 years of daily ranging data and inter-group encounter data from the Karisoke Research Center.
- Analyzed home range size using 90% kernel density estimates and quantified home range overlap between groups.
- Examined the relationship between group size, number of weaned individuals, and home range size.
Main Results:
- Gorilla groups exhibited small home ranges (average 8.07 km²) with significant between-group variation.
- High home range overlap was observed, increasing dramatically with the formation of new groups.
- Despite increased overlap, feeding competition effects were not marked, but inter-group encounters increased sixfold.
Conclusions:
- The growing Virunga mountain gorilla population shows limited evidence of feeding competition despite small home ranges and high overlap.
- Increased inter-group encounters due to habitat overlap elevate risks of injuries and infanticide.
- Continued monitoring is essential to manage population growth and mitigate risks in this protected area.
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