In 1558, when the current People's Republic of Mozambique was colonized by the Portuguese, the missionary João dos Santos observed a small brownish-colored bird glide inside his church to peck at the wax from the candles. But this was not his only ability: the bird was able to guide the men to the hives where they extracted the honey and the animals fed on the wax.
In Africa, the unusual relationship between the bird and "honey hunter" men continues to intrigue scientists and is undoubtedly one of the few instances of mutualism that exists between these two species. To understand how the bird has been able to learn to recognize the calls of men, a team of researchers has carried out experiments in the Niassa National Reserve of Mozambique together with the inhabitants of the Yao tribe.
The study, published in Science this week, reveals that men manage to recruit these birds with their peculiar sounds and thus find the hives. For their part, the ‘honey guides’ make humans their partners to access the honeycomb without being bitten by bees. Thanks to the signals of both species, humans and birds communicate and cooperate to increase their chances of locating this valuable and nutritious food.
"The most extraordinary thing about this reciprocal relationship is that it involves a wild animal whose interactions with humans have evolved through natural selection, probably over hundreds of thousands of years," emphasizes Claire Spottiswoode, lead author of the work and biologist. evolutionary at the University of Cambridge and Cape Town in South Africa.
From tree to tree to find honeycombs
The scientist went into the African forests with the inhabitants of the Yao tribe to verify that the birds were able to distinguish the specific call of these men from other human sounds, and respond to it. This sound signal made by 'honey hunters' has been passed down from generation to generation and is characterized by a loud chirp followed by a short growl.
Two hunters began their walk by making their usual calls to attract the birds while a researcher played recordings of three different sound signals every seven seconds at 15-minute intervals.
The results confirmed the two-way communication between the two species by showing that Yao calls allowed a 54% chance of finding the honeycomb, while control calls generated only 17%. "The call tripled the odds of a successful interaction, providing honey for humans and wax for birds," says Spottiswoode.
Once the birds identified the men's call, they acted as a guide to the honey, flitting from tree to tree to indicate where the combs were hidden. In 75% of cases they successfully found the hive, according to the experiment. In the task of extracting the food, the birds required the help of men to drive away the bees with smoke and break the honeycomb. The men benefited from the honey by leaving the wax for the birds.
In other regions of Africa such as Tanzania, the Hadza tribe inhabitants use other more melodic sounds for the same purpose. "We would love to know if the 'honey guides' have learned the variations of this type of language in human signals throughout Africa, which has allowed them to recognize the appropriate collaborators among the locals who live next to them" , concludes the scientist.
Bibliographic reference: C.N. Spottiswoode et al. "Reciprocal signaling in honeyguide-human mutualism" Science July 20, 2016
Photo: Honey hunter Orlando Yassene holds in his hand a male guide bird, temporarily captured for the study carried out in the Niassa National Reserve in Mozambique. / Claire Spottiswoode