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On Malgas Island, a flat landmass off South Africa’s Western Cape, Mukuzai Muyahamba scans the sky as thousands of Cape gannets circle overhead in a wheeling blur of white feathers, black tails, and yellow heads. But Muyahamba is waiting for a specific bird to return to its nest—the one with a tiny GPS tag fitted to its leg. The tag was attached to record the gannet’s foraging patterns, and Muyahamba has a video camera trained on the bird’s nest to record its most captivating behavior: its dance.
All three species of gannets perform complex bill-fencing, preening, and head-bobbing rituals during mating, but also every time they return from a foraging trip at sea. Until recently, studies of these rituals, referred to collectively as a dance, have only considered their role in reproduction.
Now, a new study led by researchers from the University of Montpellier in France and the University of Cape Town in South Africa suggests the Cape gannet’s dance contains information on feeding grounds—an avian analogue of the famous honeybee waggle dance.
Karl von Frisch’s translation of the honeybee waggle dance in the 1920s was the first clear evidence that some animals communicate through dance. Using distinctive figure-eight movements, bees tell their hive mates the precise locations of reliable food sources.
Nearly a century later, the gannet study demonstrates that dance behavior in a colonially breeding vertebrate can communicate similar information, albeit in less detail. The researchers unlocked the secrets of the gannet dance by following the behavior of 28 individual birds, tracking their foraging routes using GPS tags and filming their ritual behavior on returning to their nests.
The researchers analyzed foraging patterns and dance parameters that included 14 different behaviors associated with the dance ritual, such as bill fencing, yawning, head bobbing, sky pointing, and preening. They found that the total duration of the dance was negatively correlated with the distance and duration of foraging trips. Birds that traveled farther and longer performed shorter dances.
Of the individual ritual behaviors, preening was the most significant. The length of time a bird preens “appears to contain information on the direction to the food source,” says biological oceanographer David Grémillet, who worked on the study. Heavy preeners had fed to the west of the colony on prey kicked up by fishing trawlers off the continental shelf; whereas lighter preening indicated feeding to the south, where sardines, a natural prey species, are found. Although links between foraging and the other ritual behaviors were not found, the researchers suggest that these components might have a role in courtship and pair bonding.
“I hope the study will inspire colleagues working on seabirds and other vertebrates to test similar hypotheses, for example with penguins in Antarctica,” says Grémillet.
While the study cannot provide conclusive evidence that gannets are intentionally informing their partners and neighbors using dance, it reveals strong correlations. “What we can say is that this information is available at the gannet colony,” says Nicolas Courbin, lead author of the study.
“The researchers have made good use of new approaches to looking at animal data and distributions,” says Mark Hauber, a behavioral ecologist from the University of Illinois at Urbana-Champaign, who was not involved in the research. “They confirmed that this is not a statistical nuance, it is a robust pattern of behavior.”
The next step is to find out whether the partners and neighboring birds use the information encoded in the dance to plan future foraging trips. To test this, the researchers need to equip both the forager and its partner and neighbors with GPS tags.
“This would be challenging and very time-consuming,” says Courbin. For now, the team is focusing on immediate threats to the Cape gannet colony, which has suffered dramatic population declines over the past few decades because of overfishing.