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Western Lowland Gorillas Display Territorial Behavior, New Study Says
Groups of western lowland gorillas (Gorilla gorilla gorilla) recognize ownership of specific regions; they are also more likely to avoid contact with other groups the closer they are to the centre of their neighbors’ home range, for fear of conflict, according to a new study.
Western lowland gorillas (Gorilla gorilla gorilla). Image credit: Morrison et al, doi: 10.1038/s41598-020-60504-6.
Territoriality is widespread among apes, having been observed in gibbons, chimpanzees and humans, although is reported to be absent in orangutans and at least some populations of bonobos.
Gorillas are widely assumed to be non-territorial due to the presence of home range overlap and observations of tolerant between-group interactions.
The presence of territoriality in primates is correlated with a group’s ability to patrol it’s home range on a daily basis. However, the large sizes of gorilla groups’ home ranges suggest that they are not defendable in their entirety, as the home ranges observed in habituated western gorilla groups (11-18 km2) are far larger than the average daily path lengths of 1.7-2 km.
“Our findings indicate that there is an understanding among gorillas of ‘ownership’ of areas and the location of neighboring groups restricts their movement,” said Dr. Robin Morrison, a researcher at the University of Cambridge.
“Gorillas don’t impose hard boundaries like chimpanzees. Instead, gorilla groups may have regions of priority or even exclusive use close to the centre of their home range, which could feasibly be defended by physical aggression.”
“At the same time groups can overlap and even peacefully co-exist in other regions of their ranges. The flexible system of defending and sharing space implies the presence of a complex social structure in gorillas.”
Western lowland gorillas are difficult to track on foot because they live in dense forests.
Instead, Dr. Morrison and colleagues followed eight groups of gorillas using a network of cameras placed at 36 feeding ‘hotspots’ across a 60 km2 area in the peripheral regions of Odzala-Kokoua National Park, Republic of Congo.
They discovered that gorillas display more nuanced behaviors, and their movements are strongly influenced by the location of their neighbors — they are less likely to feed at a site visited by another group that day — and the distance from the centre of their neighbors’ home range.
“This new research changes what we know about how groups of gorillas interact and has implications for what we understand about human evolution,” said co-author Dr. Jacob Dunn, reader in evolutionary biology at Anglia Ruskin University.
“Almost all comparative research into human evolution compares us to chimpanzees, with the extreme territorial violence observed in chimpanzees used as evidence that their behavior provides an evolutionary basis for warfare among humans.”
“Our research broadens this out and shows instead just how closely we compare to our next nearest relatives.”
“Gorillas’ core areas of dominance and large zones of mutual tolerance could help with our understanding of the social evolution of early human populations, showing both the capacity for violence in defending a specific territory and the between-group affiliations necessary for wider social cooperation.”
The findings are published in the journal Scientific Reports.
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R.E. Morrison et al. 2020. Western gorilla space use suggests territoriality. Sci Rep 10, 3692; doi: 10.1038/s41598-020-60504-6
