Wild birds and humans can engage in two-way conversation to the benefit of both, researchers have revealed.
A brown bird with a penchant for beeswax, the greater honeyguide is well known for signalling to human honey hunters, issuing a squeaky, chirruping call while darting between trees to indicate the way to a bees’ nest. Once there the honey-hunters collect honey while the birds feast upon leftover wax.
But now researchers have found the communication goes both ways.
“Honey hunters use special calls to signal to honeyguides that they are eager to follow, and then honeyguides in turn use that information to chose partners who are likely to be good collaborators,” said Claire Spottiswoode, lead author of the research from the University of Cambridge and the University of Cape Town.
While such displays of biological teamwork are common between animals that have been domesticated or trained, cases involving free-living animals are rare. “It seems to be a two-way conversation between our own species and a wild animal from which both those partners benefit,” Spottiswoode added.
Writing in the journal Science, Spottiswoode and colleagues describe how they spent time in the Niassa National Reserve in northern Mozambique with honey hunters of the Yao community to unpick the nature of their relationship with the honeyguide.
The researchers found that when the honey hunters special call was used, around 75% of the time the honeyguide successfully led the way to a bees’ nest.
But the question remained whether the honey hunters’ call specifically signalled to the birds that they wanted to be guided, or whether the birds simply turned up because they recognised that humans were in the vicinity.
“This was instantly intriguing: could this really be an example of reciprocal communication between humans and a wild animal?” said Spottiswoode.
To find out, the researchers took part in 72 honey-hunting expeditions. During each of them one of three different sounds was played, one of which was the honey-hunters’ halloo: a long trill followed by a short grunt with a rising inflection known as the “brrrr-hm” call. The other two sounds, spoken words in the local language and the sounds of a common bird, were used as “controls” for comparison.
The researchers found that the honeyguides were more than twice as likely to lead the way when the “brrrr-hm” call was played compared to the other two sounds, prompting the bird to guide the party on 16 out of the 24 occasions it was played.
“[The call] reliably tells [the bird] that this just isn’t any human, this is a human who wants to cooperate,” said Spottiswoode.
What’s more, the researchers found that the “brrr-hm” call was more than three times as likely to result in the hunters actually finding a bees’ nest than the other sounds, with 54% of ventures proving successful. “We found that when we made the control sounds the honeyguides sometimes lost interest and stopped guiding,” said Spottiswoode.
While the Yao honey hunters have a particular call for the honeyguides, other cultural groups use different sounds to signal to the birds. That, the authors suggest, could mean that the honeyguides develop their own culture reflecting that of the humans they interact with.
Spottiswoode believes the new research points to an intriguing conclusion. “This suggests that honeyguides seem to attach meaning, and respond appropriately, to the signal that specifically advertises people’s’ willingness to cooperate,” she said.
Stuart West, professor of evolutionary biology at the University of Oxford agrees. “The honeyguide kind of understands what the human is saying,” says West. “If we think of domesticated animals, pets and livestock, we can train them to respond to specific signals,” he added, “but to have something like that in a wild animal is quite special.”
