Researchers have discovered that giant honeybees make Mexican waves. The discovery was published in the Journal of Experimental Biology. It shows that the phenomenon also known as ¨shimmering¨ is a defense mechanism to deter predators. The shimmering behavior was observed in Asian giant honeybees, including Apis dorsata. These bees usually build open nests in open locations like tree branches and window ledges. This makes them more vulnerable to attacks from predators.
What causes the Mexican Waves?
The shimmering effect occurs when individual bees flip their abdomen in a sequenced, coordinated manner across the entire nest. Like Mexican waves, each bee flips its abdomen after the bee to one side of them. This creates a continuous wave-like motion through the colony.
What triggers Shimmering?
The study was led by Sajesh Vijayan, a behavioral ecologist from the Indian Institute of Science Education and Research Thiruvananthapuram. Sajesh and his team wanted to find out what triggers the shimmering. For the experiment, they moved different sizes of gray and black colored round cardboard pieces in various ambient light conditions near an open hive of Apis dorsata.
They discovered that bright ambient light provoked the strongest response to shimmer. The darker the background light was, the lower the response.
They found that the honeybees repeatedly reacted only to dark objects against a light background. They did not respond when the conditions were reversed (i.e. a light stimulus against a dark background). According to the researchers, open-nesting A. dorsata colonies react strongly to dark objects against a light background because, in nature, flying predators are easier to detect against a bright sky.
Another observation the team made was that the bees showed no sign of shimmering when the paper circles were less than 4 cm in diameter. This suggests that shimmering only occurs when predators are above a certain size. They also observed that the bees remained vigilant and shimmered no matter how often the experiment was repeated. A possible explanation for this is that the bees need to stay alert against persistent hornet attacks.
Sajesh says, “We also think that shimmering is a specialized response towards hornets because it has not been reported in cases of birds attacking or birds flying past these colonies. Birds, elicit a mass stinging response.”
A possible explanation could be because birds are much larger and the bees respond by stinging rather than trying to scare the predator away according to Sajesh.
Neurobiologist Kavitha Kannan, from the University of Konstanz, Germany who was not involved in the study commented, the behavior “is intriguing as this is possibly one way in which a species of animal communicates with another to warn that they are capable of defending themselves.”