Baboons can tell whether they need to make a ruckus to get attention or if they already have a captive audience.

To see whether the animals adjust their mode of communication according to the level of an observer's attention, Marie Bourjade at Aix-Marseille University, France, and her colleagues tempted 16 captive olive baboons (Papio anubis; pictured) with a tasty fruit treat. The experimenters stood facing the animals with their eyes either open or closed, or turned away from the animals.

Baboons made more begging hand gestures when experimenters had their eyes open. When the experimenters' eyes were closed or their backs were turned, the monkeys tended to make noisy banging actions instead. Attention-getting gestures in monkeys may have been a starting point for the evolution of intentional vocal communication in great apes and humans, the researchers suggest.


Anim. Behav. (2013)