Wild African Bird Willingly Helps People Find Food
The cooperation between human hunters and wild animals is extremely rare.
Photo: Honey-Hunter Orlando Yassene holds a male greater honeyguide temporarily captured for research in the Niassa National Regional Reserve, Mozambique. Credit: Claire Spottiswoode Wild birds in Africa known as greater honeyguides willingly help people find honey, and even respond to a call -- "brrrr-hm!" -- that men in Mozambique make, a new study reports.
This unique cooperation between a human and a free-living animal, reported in the journal Science, marks only the second time that a comparable foraging partnership between wild animals and our own species has been documented. The other case involves free-living dolphins who chase schools of mullet into fishermen's nets and, in so doing, manage to catch more for themselves.
Our relationship with greater honeyguides (Indicator indicator) leads to a win-win as well, since the men get honey and the birds can access the wax and bee larvae that they crave after the humans subdue stinging bees with smoke and chop open the hive. It's a partnership that likely has lasted a very long time.
"Humans have always loved honey," lead author Claire Spottiswoode told Discovery News, adding that "honey-hunting by people has been depicted in rock art dated at circa 20,000 years ago," but that the mutualism could date back "hundreds of thousands of years."
Spottiswoode, an evolutionary biologist at both the University of Cape Town and the University of Cambridge, carried out controlled experiments in Mozambique's Niassa National Reserve with colleagues Keith Begg and Colleen Begg. The researchers observed men called "honey-hunters" from the local Yao community interacting with the birds.
The exchange can begin in two ways: The men call the birds with the "brrrr-hm" vocalization, or the birds start the process. They do this, Spottiswoode said, by flying "from tree to tree in the direction of the bees' nest. They have white outer tail feathers, which sometimes catch the eye as they fly."
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Curious about the "brrrr-hm" call, the researchers made recordings of the sound and two control sounds, which were just calls of another bird species and arbitrary words yelled out by the honey-hunters. The scientists found that the "brrrr-hm" call (a loud trill followed by a short grunt) more than tripled the chances of a meet up, yielding honey for the humans and wax for the bird.
Anecdotally, the Yao have noticed that younger greater honeyguides do not respond to the call, so Spottiswoode said that "their observations are certainly consistent with the idea that the honeyguide's knowledge of the local honey-hunting call is learned." This reinforces that we have not unwittingly domesticated the birds, which would involve genetic change.
Brian Wood, an assistant professor of anthropology at Yale University, has also extensively studied greater honeyguides. He told Discovery News that people in other parts of Africa use different calls to attract the birds. These include various spoken words, shouted words, whistles and other calls, such as the Yao's distinctive one. In each case, it's likely the local birds have learned the men's traditional call over time.
Wood said that the relationship between the wild birds and humans "is likely to be thousands, even millions, of years old, but the relationship certainly has changed through space and time, involving different acoustic attractors and different forms of 'repayment' to honeyguides."
He explained that "in some areas, birds are actively repaid by human honey hunters and in other places and times humans actively reduce the bird's 'payoff.' The relationship ... involves elements of both mutualism and manipulation."
The birds are not mere innocents either. Mother greater honeyguides, like cuckoos, exploit other species by laying their eggs in the nests of other birds. Once the chicks hatch, they are equipped with sharp hooks at the tips of their beaks that allow them to kill their foster siblings as soon as they hatch, permitting a nest takeover.
"So the greater honeyguide is a master of deception and exploitation as well as cooperation -- a proper Jekyll and Hyde of the bird world," Spottiswoode said.
Richard Wrangham of Harvard University's Department of Human Evolutionary Biology said that the traditional understanding of the guiding behavior of greater honeyguides was that it had co-evolved, not with humans, but with another species: ratels (honey-badgers). This has not been proven, however.
"So that raised the possibility," Wrangham said, "that the mutualistic relationship between honeyguides and humans is a result of direct co-evolution between those species. The new paper supports that view."
It was previously thought that the birds would respond to any unusual noise, such as car engines.
"The new finding shows that honeyguides pay special attention, not just to sounds made by humans, but specifically to the sounds that are designed by humans to attract honeyguides," Wrangham said.
Honey is not just a sweet snack, either. He shared that it sometimes supplies African hunter-gatherers with up to 80 percent of their calories per month. Greater honeyguides have therefore been benefitting our survival for ages, and vice versa.
Spottiswoode however said that "the honeyguide-human relationship has already largely vanished from many parts of Africa, so our opportunities fully to understand this relationship are fast disappearing."
She believes that is one of many reasons why Niassa National Reserve is so important.
"It's a protected area the size of Denmark," she said, "with globally important populations of elephant, lion, wild dog and other wildlife, but it is under threat from many quarters, including elephant poaching and gold mining."