According to a new research, chimpanzees are very likely to form social bonds that keep them together for prolonged periods of time. This is especially true for males, which have been reported to remain in close contact with each other for as long as 7 years. Females, on the other hand, leave the colony when they become mature enough, and are therefore less likely to create long-lasting social bonds with other females. Nearly all males engage in social activities, but the reason why they do this is still unknown.

Researcher John Mitani, who is a primatologist at the University of Michigan in the US, identified exchanging back scratches and sharing meat among the most common-met behaviors in Uganda's Kibale National Park chimp colony. Over the 10 years he spent studying the social interactions between the primates, he noted that "best friends" were more likely to go about their daily business together, in addition to grooming each other and sharing food.

In order to get to this conclusion, Mitani spent a couple of months per year in the chimp reservation, which was three times larger than any other, and noted all the interactions between designated males. In 10 years, the correlations became visible, once the researcher and his colleagues learned to distinguish and name the chimpanzees.

The primatologist drew interesting parallels between the primates' behavior and our own, saying that most of the long-lasting relationships were based on mutual respect, in that partners spent roughly the same amount of time grooming the other as they spent being groomed. The researcher said that  the ones who engaged in a mutual-beneficial type of behavior were statistically far more likely to remain friends for many years, compared with their peers.

Other scientists argued that, in the light of the new finds, parallels could be drawn between the behavior of chimps and that of baboons, whom University of California in Los Angeles primatologist Joan Silk studied in Botswana. "These similarities suggest that there are common principles for building strong bonds which extend across species," she maintained.