In 1933, American anatomist Harold Coolidge elevated it to species status. Major behavioural differences between bonobos and chimpanzees were first discussed in detail by Tratz and Heck in the early 1950s. American psychologist and primatologist Robert Yerkes was also one of the first to notice major behavioural differences.
We provided 42 captive great apes with both rough-surfaced and hairless plants. None of the subjects had previously been observed to engage in leaf swallowing behavior and were therefore assumed naïve. Two chimpanzees and one bonobo swallowed rough-surfaced leaves spontaneously without chewing them.
The downside of working at Lola and Ekolo ya Bonobo is that many of the photographs that exist of bonobos all over the world come from here—that’s what most people have already seen. For a film, you’d spend anywhere upwards of a year in the field … and that’s just so you can have a camera in place when something unusual happens. Often with animals, it all comes down to luck—being in the right place at what does pekka stand for the right time. But I was very aware on this project that we needed to build up enough time to be able to get what we got. It took a bit longer getting in and out, so in all, almost six weeks. There is no clear answer to the question of whether bonobos are smarter than chimps, but it is clear that they are markedly different mentally and emotionally, and both are simply brilliant in their own ways.
Aggressive encounters between males and females are rare, and males are tolerant of infants and juveniles. The mother–son bond often stays strong and continues throughout life. While social hierarchies do exist, and although the son of a high ranking female may outrank a lower female, rank plays a less prominent role than in other primate societies.
Chimpanzees and gorillas have suffered devastating Ebola epidemics as well. During 2002 and 2003, approximately 5,000 gorillas succumbed to this highly contagious, almost always fatal disease. The lowland gorilla population has dropped by at least 80% over the last 3 generations. However, the sexual dimorphism of siamangs is slight compared to that of the great apes. Darwin alluded to the relationship between the hair and teeth in the naked Turkish dog and wrote that ‘it can be only slightly accidental’.