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The young will have sex with the old, and males and females frequently engage in same-sex activity. Chimps, on the other hand, are much more reserved, mating primarily for procreation. For bonobos, sex seems to fulfill the role that competition plays in chimpanzees. For example, when a chimpanzee group stumbles upon a food source, the most aggressive males will often eat their fill first, frightening off all others, and leaving only scraps.
When a group of bonobos discovers a cache of food, they often have an orgy, and then everyone shares. Bonobos are actually physically built for this sexual problem solving. The clitorises of female bonobos are extremely large for the animals' size and are likely very sensitive.
While more modest in size, males' genitalia may also be similarly sensitive and thus primed to deliver "good feelings. More striking are the differences in how chimps' and bonobos' brains are wired. A study showed that bonobo brains are more developed in regions associated with empathy.
Moreover, bonobo brains feature a thick connection between the amygdala -- the brain's fear center -- and the ventral anterior cingulate cortex, a region associated with rational functions like decision-making and impulse control.
Chimps lack this developed connection, meaning that they are likely less in control of their fear and aggression. Physical and behavioral differences between chimpanzees and bonobos evolved over millions of years. Roughly two million years ago, the two species were almost certainly one. While chimpanzee males frequently band together to hunt and kill monkeys, the more peaceful bonobos were believed to restrict what meat they do eat to forest antelopes, squirrels, and rodents.
Not so, according to a study, reported in the October 14th issue of Current Biology, a Cell Press publication, that offers the first direct evidence of wild bonobos hunting and eating the young of other primate species.
By inference, the lack of male dominance and physical violence is often used to explain the relative absence of hunting and meat eating in bonobos. Our observations suggest that, in contrast to previous assumptions, these behaviors may persist in societies with different social relations.
Bonobos live only in the lowland forest south of the river Congo, and, along with chimpanzees, they are humans' closest relatives. Bonobos are perhaps best known for their promiscuity: sexual acts both within and between the sexes are a common means of greeting, resolving conflicts, or reconciling after conflicts.
The researchers made the discovery that these free-loving primates also hunt and kill other primates while they were studying a bonobo population living in LuiKotale, Salonga National Park, in the Democratic Republic of Congo. They had been observing the bonobos there for the last five years, which is what made the new observations possible.
Although Hohmann's team did have prior evidence for monkey hunting by bonobos, it came exclusively from indirect studies of fresh fecal samples—one of which contained the digit of a black mangabey.
Yet, in the absence of direct behavioral observations, it was not entirely clear whether the bonobos had hunted the mangabey themselves or had taken it from another predator. The researchers have now seen three instances of successful hunts in which bonobos captured and ate their primate prey.
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