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Inter‐group relationships influence territorial defence in mountain gorillas
Author(s) -
Morrison Robin E.,
Hirwa Jean Paul,
Mucyo Jean Pierre S.,
Stoinski Tara S.,
Vecellio Veronica,
Eckardt Winnie
Publication year - 2020
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/1365-2656.13355
Subject(s) - territoriality , aggression , context (archaeology) , home range , social relationship , social group , social relation , psychology , social environment , social psychology , geography , demography , ecology , biology , communication , sociology , habitat , social science , archaeology
Many species show territoriality, in which territory owners have exclusive or priority use of a region. In humans, tolerance of others within our space also depends greatly on our social relationships with them. This has been hypothesized as one potential driver of the evolution of long‐term, inter‐group relationships, through enabling shared access of resources and easing disputes over space. However, extremely little is known about the importance of social relationships between neighbouring groups in non‐humans for how space is used and shared. Using 16 years of data on the simultaneous movement and interaction patterns of 17 mountain gorilla groups, we investigated how the occurrence of aggressive and affiliative behaviour during inter‐group encounters was influenced by both their social and spatial context. We found evidence of territorial defence, with rates of aggression increasing towards the centre of home ranges. Groups which had previously split from each other showed higher levels of affiliation during encounters with each other and experienced lower levels of aggression when within the other's peripheral home range. However, encounters within core areas of the home range consistently elicited higher aggression, regardless of the groups' history. Our findings indicate that not only are the social relationships between groups retained after they split from one another but also that these relationships enable groups to access certain areas with a reduced risk of aggression. This suggests that reduced aggression when accessing areas within neighbours' home ranges may be an advantage for the maintenance of inter‐group relationships and a potential driver in the evolution of long‐term, post‐dispersal relationships and complex multi‐level societies.