The Ngogo Chimpanzee Project, started by John Mitani and David Watts in 1995, has followed chimpanzees in Kibale National Park for decades. The finding appears in Science and raises questions about chimpanzee social behaviour.
When observers began work there were more than 100 members and the group later grew to about 200. From 1998 to 2014 the chimpanzees lived as one unit. In 2015 aggression rose between two subgroups, called central and western, and they began to isolate. In 2016 the western group sent a territorial patrol and males fought. In 2018 western chimpanzees killed a young adult male. Over the next seven years members of the western group killed seven mature males and 17 infants. At the split the western group had 76 and the central group 116. The central group did not retaliate.
Mitani said chimpanzees treat outsiders as enemies regardless of past relationships. Aaron Sandel said the case challenges ideas that human warfare is driven mainly by cultural markers and points to shifting alliances and rivalries. Mitani noted several factors may have caused the split, including the group's large size and earlier deaths of males in 2014, and he stressed the value of long-term federally supported research.
Difficult words
- aggression — hostile or violent behaviour toward others
- subgroup — a smaller group within a larger groupsubgroups
- isolate — to separate from others or make lonely
- territorial patrol — a group moving to protect their area
- retaliate — to fight back or take revenge
- outsider — a person or animal from another groupoutsiders
- alliance — a partnership for support between groupsalliances
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Discussion questions
- Why is long-term research useful for studying animal behaviour like this?
- Why do you think the central group did not retaliate after the attacks?
- What can this chimpanzee case tell us about human conflicts and alliances?
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