In northern Mozambique, local honey-hunters use vocal signals to communicate with wild honeyguide birds to locate and harvest honey. New research finds that human calls used across the region vary, but the birds learn these subtle differences and continue to cooperate with their human partners, guiding them to wild bees’ nests.
The study focused on Mozambique’s 42,000-square-kilometer (16,000-square-mile) Niassa Special Reserve, where honey-hunters work with greater honeyguides (Indicator indicator), small brown birds that eat larvae and wax. With a bird’s-eye view, honeyguides locate bees’ nests and lead honey-hunters to them. People then use tools to open the nest for honey and leave behind the exposed wax and larvae for the birds. This ancient partnership can be found in a handful of areas across Africa.
Niassa honey-hunters use three distinct calls to attract their bird partners. Two function as “recruitment calls,” attracting the birds’ attention, while a third “coordination call” keeps them engaged once the hunt is underway.
Researchers examined recordings of 131 honey-hunters from 13 villages. The three principle calls involved combinations of shrill whoops, low trills and grunts, and the presence or absence of whistles. The calls varied between villages and those differences increased with distance between communities, much like human dialects.
If honey-hunters move to live in other villages, they adopt the local calls, behavioral ecologist Jessica van der Wal, the study’s lead author, told Mongabay.
“If a certain village is using a different call,” said van der Wal, “it probably means that’s the call to get the most honey, so why wouldn’t you adapt to that?”
Van der Wal described traveling with a honey-hunter from the village of Mbamba to Gomba, 100 km (60 mi) away near the Tanzanian border. The Mbamba hunter was surprised by the different calls and honey-harvesting techniques used by Gomba honey-hunters.
Despite this variability from their human partners, the birds’ willingness to cooperate was unaffected, which is notable because honeyguides are known to show bias against unfamiliar calls.
Van der Wal said the relatively small territorial ranges of honeyguides means that individual birds likely encounter hunters from only one or two nearby villages, whose calls are similar.
Still, call differences across wider parts of the reserve suggest these signals may continue to evolve over generations.
Judith Bronstein, a distinguished professor of ecology and evolutionary biology at the University of Arizona who was not involved in the study, praised the careful research on a rare example of human-animal mutualism.
“Probably in all cases, mutualisms are maintained by a combination of flexible, learned behaviors and evolved traits,” she said.
“In this case, humans signal to the birds differently in different places; the birds, which are very smart, quickly learn the local dialects. This makes the interaction robust to change and helps explain how it has persisted across diverse cultural and environmental settings across Africa.”
Banner image: Carvalho Nanguar, honey-hunter from northern Mozambique, with a male greater honeyguide released from the hand after being caught for research purposes. This photo is illustrative of the special relationship between wild honeyguides and the humans they guide to wild bees’ nests. Photo courtesy of David Lloyd-Jones and Dominic Cram.
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