While it has long been known that modern chimpanzees use tools, recent research indicates that chimpanzee stone tool use dates to at least 4300 years ago. A recent study revealed the use of such advanced tools as spears, which West African Chimpanzees in Senegal sharpen with their teeth, being used to spear Senegal Bushbabies out of small holes in trees. An Eastern Chimpanzee has been observed using a modified branch as a tool to capture a squirrel. A Common Chimpanzee from the Kasakela chimpanzee community was the first non-human animal observed making a tool, by modifying a twig to use as an instrument for extracting termites from their mound.
Common Chimpanzees live in communities that typically range from twenty to more than 150 members, but spend most of their time travelling in small parties of just a few individuals. They are both arboreal and terrestrial, spending equal time in the trees and on the ground. Their habitual gait is quadrupedal, using the soles of their feet and resting on their knuckles, but they can walk upright for short distances. Common Chimpanzees are 'knuckle walkers', like gorillas, in contrast to the quadrupedal locomotion of orangutans and bonobos, 'palm walkers' who use the outside edge of their palms.
The Common Chimpanzee lives in a fission-fusion society, where mating is promiscuous, and may be found in groups of the following types: all-male, adult females and offspring, consisting of both sexes, one female and her offspring, or a single individual. At the core of social structures are males, who roam around, protect group members, and search for food. Among males, there is generally a dominance hierarchy. However, this unusual fission-fusion social structure, "in which portions of the parent group may on a regular basis separate from and then rejoin the rest," is highly variable in terms of which particular individual chimpanzees congregate at a given time. This is mainly due to chimpanzees having a high level of individual autonomy within their fission-fusion social groups. Also, communities have large ranges that overlap with those of other groups.
As a result, individual chimpanzees often forage for food alone, or in smaller groups (as opposed to the much larger parent group, which encompasses all the chimpanzees who regularly come into contact and congregate into parties in a particular area.) As stated, these smaller groups also emerge in a variety of types, for a variety of purposes. For example, an all-male troop may be organized in order to hunt for meat, while a group consisting of one mature male and one mature female may occur for the purposes of copulation. An individual may encounter certain individuals quite frequently, but have run-ins with others almost never or only in large-scale gatherings. Due to the varying frequency at which chimpanzees associate, the structure of their societies is highly complicated.
Chimps are highly territorial and are known to kill other chimps. Groups of male chimps patrol the borders of their territory and will brutally attack any foreign chimp that trespasses. Of course patrol parties from smaller groups are more likely to avoid contact with their neighbors. Patrol parties from large groups will even take over a smaller group's territory, gaining access to more resources, food and females.
When confronted by a predator, chimpanzees will react with loud screams and use any object they can get against the threat. As noted above, the leopard is the chimp's main natural predator, but they have fallen prey to lions as well.