From Marginal Revolution, reblogging the NYT: 

"Now scientists have determined that humans and their honeyguides [a kind of bird] communicate with each other through an extraordinary exchange of sounds and gestures, which are used only for honey hunting and serve to convey enthusiasm, trustworthiness and a commitment to the dangerous business of separating bees from their hives.

The findings cast fresh light on one of only a few known examples of cooperation between humans and free-living wild animals, a partnership that may well predate the love affair between people and their domesticated dogs by hundreds of thousands of years.

Claire N. Spottiswoode, a behavioral ecologist at Cambridge University, and her colleagues reported in the journal Science that honeyguides advertise their scout readiness to the Yao people of northern Mozambique by flying up close while emitting a loud chattering cry.

For their part, the Yao seek to recruit and retain honeyguides with a distinctive vocalization, a firmly trilled ‘brrr’ followed by a grunted ‘hmm.’ In a series of careful experiments, the researchers then showed that honeyguides take the meaning of the familiar ahoy seriously.

…Researchers have identified a couple of other examples of human-wild animal cooperation: fishermen in Brazil who work with bottlenose dolphins to maximize the number of mullets swept into nets or snatched up by dolphin mouths, and orcas that helped whalers finish off harpooned baleen giants by pulling down the cables and drowning the whales, all for the reward from the humans of a massive whale tongue.

But for the clarity of reciprocity, nothing can match the relationship between honeyguide and honey hunter. ‘Honeyguides provide the information and get the wax,’ Dr. Spottiswoode said. ‘Humans provide the skills and get the honey.’

Very interesting. May I suggest you watch the beautiful BBC documentaries, Human Planet. You'll see a video of these Brazilian fishermen.