Chimps can barter food, understand trade

Journal of Comparative Psychology:

Researchers shed light on trading behavior in animals -- and humans
Georgia State's Sarah Brosnan, assistant professor of psychology, and research scientist Michael Beran conducted a study to see if chimpanzees spontaneously bartered foods among each other, using tokens which represented those foods. While results indicated that the animals were cognitively able to understand trade, without enforcement from human experimenters, trade disappeared.