Chimpanzees Observed Using Weapons

Chimpanzees in Senegal have been observed making and using wooden spears to hunt other primates, according to a study in the journal Current Biology. Researchers documented 22 cases of chimps fashioning tools to jab at smaller primates sheltering in cavities of hollow branches or tree trunks. Chimps had not been previously observed hunting other animals with tools.

Chimpanzees were observed jabbing the spears into hollow trunks or branches, over and over again. After the chimp removed the tool, it would frequently smell or lick it. In the vast majority of cases, the chimps used the tools in the manner of a spear, not as probes. The researchers say they were using enough force to injure an animal that may have been hiding inside. Adolescent females exhibited the behavior most frequently.

In most cases, the chimpanzees carried out four or more steps to manufacture spears for hunting. In all but one of the cases, chimps broke off a living branch to make their tool. They would then trim the side branches and leaves. In a number of cases, chimps also trimmed the ends of the branch and stripped it of bark. Some chimps also sharpened the tip of the tool with their teeth.

Many areas where chimpanzees live are also home to red colobus monkey, which the chimps hunt. However, the Senegal site is lacking in this species, so chimps may have needed to adopt a new hunting strategy to catch a different prey - bushbaby.