Abstract
Group-living animals face a number of threats from extragroup conspecifics: from individuals seeking mating opportunities to rival groups attempting to access limited resources. The consequences of intergroup interactions can therefore include loss of mates, increased energy expenditure, and injury or death. There is increasing evidence that aggressive intergroup interactions can affect subsequent intragroup behavior, and that such post-conflict behavior may be directly related to the threats posed by different opponent groups (e.g., familiar vs. unfamiliar). However, empirical evidence for changes in intragroup behavior following intergroup conflict in social animals is limited. We compared the proximity and behavior of group members before and after 84 aggressive intergroup interactions involving 14 study groups of wild, habituated mountain gorillas (Gorilla beringei beringei) in Volcanoes National Park, Rwanda. Intergroup conflict affected subsequent intragroup behavior in several ways. We found that immediate movement away from the opponent following intergroup conflict was less likely between familiar groups compared to unfamiliar groups. However, both winning and losing groups spent twice as much time moving post-conflict, and losing groups spent less time resting. There was an increase in female intragroup affiliative interactions and a decrease in male intragroup agonistic interactions post-conflict. These results demonstrate that such intergroup contests can influence intragroup dynamics beyond the immediate period of interaction.
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Acknowledgments
We wish to thank Rwanda Development Board and Ministry of Education, Rwanda for permission to conduct research in the Volcanoes National Park. We thank DFGFI for the research collaboration and the ongoing support and are incredibly thankful to all the Karisoke trackers, field assistants, and researchers over the study period who conducted the vast majority of the demographic and behavioral data collection used in this project. Special thank you to the field coordinators over the study period—Bosco Bizumuremyi, Fidele Uwimana, Francois Xavier Ndungutze (Conseiller), and Jean Damascene Hategekimana (Fundi)—for overseeing the maintenance of high quality of data collection. Special thanks to Didier Abavandimwe for the creation of the interaction database specifically for this project and Damien Caillaud, for statistical support. Thank you to Martha Robbins and the reviewers for the constructive and insightful feedback that greatly improved the manuscript. We are very appreciative for the time and effort from Sarie Van Belle, Cyril Grueter, and Takeshi Furuichi to create this special issue. This project was funded by Cyril Grueter’s project grant (School of Human Sciences, University of Western Australia, grant number 10301036).
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CCG, MOM and ARR developed the idea, MOM, JPMS, VV, FN, TSS, CCG collected the data, MOM analyzed the data and wrote the manuscript; ARR, VV, TSS and CCG provided editorial advice.
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Mirville, M.O., Ridley, A.R., Samedi, J.P.M. et al. Intragroup Behavioral Changes Following Intergroup Conflict in Mountain Gorillas (Gorilla beringei beringei). Int J Primatol 41, 382–400 (2020). https://doi.org/10.1007/s10764-020-00130-1
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DOI: https://doi.org/10.1007/s10764-020-00130-1