Cooperation
Coalitions
Watts (2002) stresses the importance of associations among chimpanzees.
Social relationships in non-human primates result from pursuing fitness-maximizing
strategies. Repeated coalitions form alliances, and alpha males depend on
others to retain their position. Most coalitions form when two or more males
direct aggression at a usually subordinate third party. Also, males associate
with males relatively close in age rather than based on maternal relatedness.
Reciprocity and interchange attain and maintain social bonds; these acts are the result of mutualism, not reciprocal altruism. Reciprocity is the exchange of the same act, while interchange is the exchange of different kinds of acts. However, benefiting from social exchange requires complex cognitive capacities. Grooming, the most common activity, exhibits a “you scratch my back, I’ll defend yours” mentality. Chimpanzees preferentially groom high-ranking individuals, causing the higher chimp to defend the lower in a future agonistic encounter. Male-male grooming is most common, and lower males use it to lower the amount of aggression they receive. Grooming increases willingness of non-relative to support in agonistic interactions (Watts, 2002).
Hunting
Stanford (1996) explains that chimpanzees are hunters, cooperate with others,
and share obtained food. There is a strong correlation between party size
and hunting success, suggesting the importance of teamwork. Hunting serves
nutritional purposes, by eliminating competition for a food source, as well
as social purposes, by exhibiting male prowess. Hunting of the red colobus
monkey is so intense, chimpanzees are the limiting factor on colobus group
size and population growth. However, chimps will also come across piglets
and bushbuck fawns, and will kill them as well. Killing patterns depend on
foraging: when bananas were offered at Gombe, chimpanzees encountered more
baboons than colobus monkeys, and incidentally killed more baboons.
Calories gained from meat are relatively small. In fact, the oil palm nut
has eight times as many calories/kilogram and higher unsaturated fat than
meat, and is available year round. This suggests that chimps do not hunt
for nutritional gain, but to strengthen group bonding. Role-taking and
highly coordinated actions drive the colobus monkey into the open. Upon capture,
chimps use the monkey’s arms to flail the victim against the ground
or a tree, and typically consume the brain first. Chimpanzees consume flesh
as well as viscera and bone. The kill is made with a cranio-cervical bite,
the head is quickly bitten off, and the brain is sucked out and eaten.
Chimps do not scavenge due to the social aspect that is lost by not hunting
together
(Stanford, 1996). Meat is an important tool in chimpanzee society; alliances
are cemented by meat gifts. Captured meat is shared evenly or strategically,
for nutritional or political reasons (Stanford, 1998).