Science: A Sweet Example of Human and Wild Animal Collaboration
How do honey-hunters in Mozambique ask honeyguide birds for help in finding a sweet treat they can share? | BBSRC
When a honey-hunter in Mozambique makes a distinct "brrr-hm!" sound, honeyguide birds fly to him, and appear to know that the hunter needs help tracking down a bees' nest.
This remarkable partnership, described in a study published in the 22 July issue of Science, reveals how birds can attach specific meaning to a human's call, and represents a rare case of mutual cooperation between humans and a wild animal.
Indicator indicator, known as the greater honeyguide, is a bird species that flits from tree to tree, showing humans where beehives are hidden. Alone, the bird is unable to crack open a beehive to enjoy the beeswax within. Yet, after humans harvest a hive for honey, they leave behind the wax, and, with that, compensate the honeyguides with a delicious treat.
Claire Spottiswoode of the University of Cambridge, has been fascinated with this bird species most of her life. When she encountered Keith and Colleen Begg, with whom she co-authored the Science study, they told her that honey-hunters from the Yao tribe in the Niassa National Reserve in Mozambique use a distinct "brrr-hm!" sound to attract honeyguides.
"This was instantly intriguing — could this really be an example of reciprocal communication between humans and a wild animal?" Spottiswoode said. "We knew from [another researcher's] work that honeyguides definitely communicate to humans — their calls and behavior indicate the direction of bees' nests — but the Yao honey-hunters' claim implied that humans communicate to honeyguides, too."
To investigate, Spottiswoode and colleagues interviewed 20 Yao men who use the "brrr-hm!" call, all of whom say their fathers taught them the call, and that it's the best way to attract a honeyguide. The researchers then trailed honey-hunters to find out how the two species might be communicating. "In particular, we wanted to distinguish whether honeyguides responded to the specific information content of the 'brrr-hm!' call, which effectively signals 'I am looking for bees' nests,' or whether the call simply alerts honeyguides to the presence of humans," explained Spottiswoode.
The trio made recordings of the call, along with the sound of hunters calling out the Yao words for "honeyguide…honey" and another animal sound. Then, a researcher and a local honey-hunter walked while playing back one of the three sounds every seven seconds over 15-minute intervals. Birds were much more likely to respond to the "brrr-hm!" call meant to attract them than they were to the other sounds, the researchers found.
The traditional call for cooperation increased the probability of a hunter being led to a nest by a honeyguide to 66% from 33%, and increased the overall probability of being shown a bees' nest to 54% from 16% compared with the other sounds.
Spottiswoode noted that honeyguides sometimes lost interest and stopped guiding the group when they played back the Yao words or animal sound. In contrast, the distinct "brrr-hm!" call dramatically increased a hunter's chances of attracting a honeyguide and ultimately finding honey. "This suggests that honeyguides attach meaning and respond appropriately to this signal that advertises peoples' willingness to cooperate," she said. "So it seems to be a two-way conversation between our own species and a wild animal, from which both partners benefit."
Intriguingly, another tribe of hunter-gatherers in northern Tanzania, the Hadza, are known to have a similar relationship with the greater honeyguide, yet they use a different type of call — a melodious whistle — to attract the birds. "This raises the intriguing possibility that there might be a mosaic of honeyguide cultural variation across Africa, that reflects that of their human partners," Spottiswoode said.
Next, her team plans to test whether greater honeyguides learn about their human partners' signals over time. "Ultimately, we'd love to know whether human culture and honeyguide traditions coevolve with one another across Africa," she said.
[Credit for related image: Claire Spottiswoode]