Show me a sign of sweetness to come Communication between humans and domesticated animals is common. Regular communication between humans and wild animals, however, is rare. African honey-guide birds are known to regularly lead human honey-hunters to bee colonies, and the humans, on opening up the nest, leave enough mess for the birds to feast on. Spottiswoode et al. show that when the honey-hunters make a specific call, honey-guides are both more likely to come to their aid and more likely to find them a bee's nest. This interaction suggests that the birds are able to attach a specific meaning of cooperation to the human's call—a rare case of mutualism between humans and a wild animal. Science , this issue p. 387
