African honeyguide birds understand and respond to the culturally distinct signals made by local human honey hunters, suggesting cultural coevolution between species, according to a new study. Although the animal kingdom is full of interspecific mutualism, systems in which humans successfully cooperate with wild animals are rare. One such relationship involves the greater honeyguide (Indicator indicator), a small African bird known to lead humans to wild bees' nests. Humans open the nests to collect honey, and the honeyguides eat the exposed beeswax. Human honey hunters in different parts of Africa often use specialized and culturally distinct calls to signal they are looking for a honeyguide partner and to maintain cooperation while following a guiding bird. For example, honey hunters from the Yao cultural group in northern Mozambique use a loud trill followed by a grunt ("brrr-hm"). In contrast, honey hunters from the Hadza cultural group of northern Tanzania use a melodic whistle. These successful calls have been maintained in these groups for generations. In a series of field experiments across these areas, Claire Spottiswoode and Brian Wood investigated whether honeyguides are more likely to respond to signals of their local human culture than to those of another culture or to arbitrary human sounds. Spottiswoode and Wood discovered that honeyguides in the Yao area were more than three times more likely to initiate a guiding response to the Yao's distinct call than the Hadza's whistle. Conversely, honeyguides in the Hadza area were more than three times as likely to respond to the Hadza's whistle than the Yao's brrr-hm. According to the authors, the geographic variation and coordination between signal and response observed in this behavioral system suggests cultural coevolution between honeyguides and humans has occurred. In a related Perspective, William Searcy and Stephen Nowicki discuss the study and its findings in greater detail.
For reporters interested in trends, this study builds on previous work published in a July 2016 Report in Science, which demonstrated the reciprocal signaling in honeyguides and honey hunters in Mozambique.
