Chimpanzees

Several projects begun in the early 1970s were the first to study bonobos in the wild. Their alternative name, pygmy chimp, is inaccurate because these animals are only slightly smaller than common chimpanzees. The reference to "pygmy" has more to do with so-called pedomorphic traits of bonobos, meaning they exhibit certain aspects of adolescence in early adulthood, such as a rounded shape of their head.

Another characteristic of the bonobo that differs from the common chimp is the joining of two digits of their foot. Additionally, the bonobo's body frame is thinner, its head is smaller, its shoulders narrower, and legs are longer and stretch while it is walking. Furthermore, the eyebrow ridges of the bonobo are slimmer, its lips are reddish with a black edge, its ears are smaller, and its nostrils are widely spaced. Bonobos also have a flatter and broader face with a higher forehead than do common chimpanzees, and their hair is blacker and finer.

Bonobos also have a somewhat more complex social structure. Like common chimpanzees, bonobos belong to large communities and form smaller groups of six to 15 that will travel and forage together. Groups of bonobos have an equal sex ratio, unlike those of the common chimpanzee. Among bonobos the strongest bonds are created between adult females and between the sexes. Bonds between adult males are weak (whereas in common chimps they may be strong). Bonobo females take a more central position in the social hierarchy of the group.

Sex is an important pastime among bonobo chimpanzees. Female bonobos are almost always receptive and are willing to mate during most of their monthly cycle. The ongoing sexual exchanges within their communities help to maintain peace and ease friction. Bonobos try to avoid social conflict, especially when it relates to food.

Bonobos are extremely acrobatic and enjoy spending time in the trees. They do not fear water and have been observed to become playful on rainy days, unlike common chimpanzees who hate the rain. It is believed that there are fewer than 100,000 bonobos in the wild; they are threatened by hunting as food and for sale in foreign trade, and by the destruction of their natural forest habitat.