Credit: Claire Spottiswoode
For an undetermined period of time – probably measured in tens of thousands of years – certain traditional cultures in Africa have regularly communicated with birds who, when they trust the humans, lead them to honey-packed bee hives. The birds’ motivation is to be able to feast on insects and beeswax the bee hunters leave behind for them.
One species has recently been studied in Mozambique by researchers from Cambridge University. Their findings, published this month (July) in the journal Science, are said to be the most extensive ever reported on this cross-species working relationship. There are, however, two videos on YouTube (one immediately after the other) which show Africans in action communicating via special sounds with honeyguides – with the latter leading tghen the honey hunters right to trees containing hives. As they approach the ‘target’ tree, one video says, the birds vary their calls to indicated the hunters “are getting hotter” – closer to the hive-bearing tree.
This is thought to be the only instance of a species of wild birds communicating with humans, and vice versa. (A New York Times report on the Science article called this “one of only a few known examples of cooperation between humans and free-living wild animals, a partnership that many 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, acting as spokesperson for the honeyguides research team, told The Times that the birds “advertise their scout readiness to the Yao people of northern Mozambique, a major Bantu ethnic and linguistic group, 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.
“The birds were twice as likely to offer sustained help to Yao foragers who walked along while playing recordings of the proper brrr-hmm signal than they were to participants with recordings of normal Yao words or the sounds of other animals,” The Times’ article said.
“The fact that the honeyguides were responding more to the specialized sound implies they recognize the specific information content in the signal,” Dr. Spottiswoode said. “It’s not simply a cue to human presence. It’s a signal that the person will be a good collaborator.”
John N. Thompson, a distinguished professor of ecology and evolutionary biology at the University of California, Santa Cruz, said: “I think it’s an absolutely terrific paper. This is one of those ‘just-so’ natural history stories we’ve known for years, and now we’ve got some hard-won data to show it really is so.”
The report describes in detail the trans-species collusion to enjoy the fruits of bee labor. Bees transform gathered nectar and pollen into honey for food and wax for honeycomb housing. As honey is among the most energy-rich foods in nature, it is not surprising that bees guard it with their lives.
African bees are particularly aggressive and will swarm any intruder that so much as jiggles an adjoining branch. Even our closest relatives are loath to disturb a beehive.
The Yao know what to do to subdue bee defenses. They wedge a bundle of dry wood wrapped in palm fronds onto a long pole, set the bundle on fire, hoist it up and rest it against a beehive in a tree. When most of the bees have been smoked out, the Yao chop down the tree, tolerate the stings of any bees that remain and scoop out the liquid gold within.
Much harder for the Yao is finding the hives. That’s where the honeyguides come in. Not only can they easily flit from tree to towering tree; they have unusually large olfactory bulbs, and they are good at smelling wax, which makes up a good part of their diet.
“It’s decidedly odd to eat wax, but if you’ve got the metabolism to break it down, it’s a good source of calories,” Dr. Spottiswoode said.