It’s not clear how honeyguides learn to interpret the Yao signals, especially since they’re cuckoo-esque parasites. The females lay their eggs in the underground nests of bee-eaters, and their chicks always hatch first. When the young bee-eaters emerge, the honeyguide chick stabs them to death with a wicked spike on its bill. It can then monopolize the attentions of its foster parents.
This grisly habit, which Spottiswoode filmed in 2011, means that honeyguides have no opportunity for learning from their parents. She suspects that they’re born with the basics of guiding behavior, and then refine their technique by watching other adults in the vicinity of bees’ nests. They certainly seem to get better as they get older. The Yao say that the youngsters (which they treat as a different species thanks to their yellow feathers) are rubbish guides, and don’t respond to the Brrrr-hm. Only the adults are worth their time.
The Yao, like many other honey-hunting societies, make sure to reward their partners. “They make quite a song and dance about it,” says Spottiswoode. “They gather up bits of wax and present it on fresh, green leaves—a little honeyguide salad.”
The Hadza are an exception. In his work, Brian Wood never saw them paying their guides. Quite the opposite: they would often hide, bury, or burn any honeycombs they didn’t collect. This, they said, keeps the birds hungry and makes them more motivated guides.
Wood and Spottiswoode are now teaming up to study how human-honeyguide communications vary from place to place. “In some areas, birds are actively repaid by honey hunters and in other places and times, humans actively reduce the bird's payoff,” says Wood.
He thinks these partnerships are ancient ones, too. It’s hard to pin a date on them, but anthropologist Richard Wrangham thinks that they may pre-date our own species. A couple of million years ago, when early hominids mastered fire, they also gained a way of subduing bees by smoking them out. That could have set the foundations for our symbiosis with honeyguides. “There are a number of reports of honeyguides being stung to death by bees, so in the absence of fire, eating wax is a risky business,” says Spottiswoode.
But if that’s the case, what was the greater honeyguide doing before we came along? Genetic studies suggest that the it evolved three million years ago, well before any hominid started harnessing flames. It’s often said that honeyguides cooperate with other species like honey badgers but that’s a myth. It became popular knowledge after unscrupulous documentary-makers who filmed a tame honey badger interacting with a stuffed honeyguide. But in reality, there’s no evidence for such a partnership. You wouldn’t expect to find any either, since honey badgers have poor eyesight and hearing, and are largely nocturnal.
It should soon be possible to work out what honeyguides did before they guided. In many parts of Africa, people just get their honey from beekeepers. In others, they replace the stuff with sugar and other sweet food. “If you can do that, why bother finding wild bees’ nests and risk getting stung?” says Spottiswoode. “I’ve worked in Zambia, where the honeyguides are common, but there’s not a lot of guiding. It seems to be dying out, bit by bit.”