Chimp likes to make friends like people

Every individual in human society needs a friend and a chimpanzee too. A 10-year study demonstrated that most male chimpanzees build long-term relationships with each other until adulthood.

John Mitani, a University of Michigan primate expert, said the male chimpanzee relationships last an average of 7 years. He observed chimpanzees in many forests of Uganda's Kibale National Park for 10 years to draw this conclusion.

For a decade, John spent a lot of time filming every activity of 35 male chimpanzees. Female chimpanzees often leave the herd when they enter estrus, so they have fewer friends than males.

Just like in human society, it seems that the strongest ties of chimpanzees are built in the spirit of mutual respect and reciprocity. The chimpanzees grooming each other for roughly the same time tend to have sex longer.

Three chimpanzees in Taronga Zoo in Sydney, Australia.Photo: msnbc.com.

The blood relationship also plays an important role in chimpanzee's friendship. John found that babies born to the same mother were more likely to have long-term relationships than other couples. However, the probability of male chimpanzees having the same father becomes close friends is no higher.

Most of the 35 male chimpanzees that John tracks have at least one long-term relationship and some have many 'close friends'. Only two children never create close relationships with other individuals during the study. However, both play with an adult male chimpanzee with their parents with them.

Joan Silk, a primate of the University of California (USA), said the chimp friendship is not much different from the friendship of baboons. In a study of Botswana baboons, Joan found that adult females often make friends with each other to groom each other. The female baboons have the same father or mother to play together longer. The relationship will quickly end if a child gives more than receives or vice versa.