Western gorilla space use suggests territoriality

Robin E Morrison,Germán Illera,Jacob C Dunn,Peter D Walsh,Magdalena Bermejo

doi:10.1038/s41598-020-60504-6

Abstract

The evolutionary origins of how modern humans share and use space are often modelled on the territorial-based violence of chimpanzees, with limited comparison to other apes. Gorillas are widely assumed to be non-territorial due to their large home ranges, extensive range overlap, and limited inter-group aggression. Using large-scale camera trapping, we monitored western gorillas in Republic of Congo across 60 km2. Avoidance patterns between groups were consistent with an understanding of the “ownership” of specific regions, with greater avoidance of their neighbours the closer they were to their neighbours’ home range centres. Groups also avoided larger groups’ home ranges to a greater extent, consistent with stronger defensive responses from more dominant groups. Our results suggest that groups may show territoriality, defending core regions of their home ranges against neighbours, and mirror patterns common across human evolution, with core areas of resident dominance and larger zones of mutual tolerance. This implies western gorillas may be a key system for understanding how humans have evolved the capacity for extreme territorial-based violence and warfare, whilst also engaging in the strong affiliative inter-group relationships necessary for large-scale cooperation.

Highlights

The evolutionary origins of how modern humans share and use space are often modelled on the territorial-based violence of chimpanzees, with limited comparison to other apes
These results demonstrate that avoidance was not based on other groups’ current locations alone but was influenced by their location relative to their neighbours’ home ranges, suggesting that the home ranges of neighbouring groups restrict gorilla movement, in addition to the actual location of conspecifics
Our results show that gorillas avoid their neighbours’ actual location, but factor in the location of their conspecifics’ ranges in the movement decisions they make

Summary

Introduction

The evolutionary origins of how modern humans share and use space are often modelled on the territorial-based violence of chimpanzees, with limited comparison to other apes. Mountain gorilla (Gorilla beringei beringei) groups have been found to use the core areas of their home ranges almost exclusively and avoid neighbouring groups[25,31] They have been found to reduce their home ranges in response to increased population density[14], an avoidance behaviour typically observed in territorial species, demonstrating that the presence of neighbouring groups represent a social barrier constraining movement patterns. This led the authors to suggest that mountain gorillas may be intermediate on a continuum between non-territoriality and territoriality[14,25]

Methods

Results

Conclusion