Friendship between chimpanzee pals is determined on the basis of trust, as amongst human beings, says an interesting study.
"Our findings suggest that current characteristics of human friendships have a long evolutionary history and extend to primate social bonds," said Jan Engelmann of the Max Planck Institute for Evolutionary Anthropology in Germany.
Chimpanzees showed a comparable pattern and extended trust selectively toward those individuals they are closely bonded with, the findings revealed.
"Chimpanzees form close and long-term emotional bonds with select individuals. These animal friendships show important parallels with close relationships in humans. One shared characteristic is the tendency to selectively trust friends in costly situations," the researchers explained.
Experimental interactions between the chimps showed much greater trust between friends than non-friends, the researchers said.
To find out whether the interactions between chimpanzees were based on trust, the researchers observed the interactions of 15 chimpanzees living at Sweetwaters Chimpanzee Sanctuary in Kenya over a five-month period.
Based on friendly interactions among chimp pairs, including grooming and eating together, the researchers identified each chimpanzee had a closest "friend" and a "non-friend", the findings published in the journal Current Biology, showed.