Here’s what triggers giant honeybees to ‘shimmer’

Giant honeybees create waves of movement across their nests by turning their abdomens up in coordination. This is a sight predators seem to avoid. New research has revealed details about the triggers of this behavior, called shimmering.

That The strongest form of shimmering isResearchers report that bees respond to a dark object being shown against a background of bright ambient light. Journal of Experimental Biology. The experimental setup simulates animals such as hornets, one of the bees’ main predators, flying against the bright sky, and shows what visual cues set off the behavior, the researchers say.

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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,” says Kavitha Kannan, a neurobiologist at the University of Konstanz in Germany who was not involved in the study.

Giant honeybees are found throughout the world, Apis dorsataThe solitary genus, a swarm of frogs, forms open nests in exposed areas such as window ledges and tree branches. Researchers used two materials in the new study. A. dorsata Nests built in roof rafters. Sajesh, a behavioral ecologist, moved round cardboard pieces in various sizes against either a gray background or a black background while he stood near the hives. The bees sparkled when a black object was placed against a gray background, but not when the contrast is flipped.

That’s probably because the black-on-gray setup “resembles a natural predator or a natural condition,” says Sajesh, who goes by his first name, as is common in many parts of southern India. “These are open-nesting colonies, so they are always exposed to a bright sky.”

The team noticed little shimmering between dawn and dusk in dimly lit areas. Researchers believe other defensive responses might also be in play when the conditions are dim.

“We also think that shimmering is a specialized response towards hornets because it has not really been reported in cases of birds attacking or birds flying past these colonies,” Sajesh says. Birds, instead, “elicit a mass stinging response.” That could be because approaching birds loom comparatively large in the bees’ visual field, and at that point, the bees’ attitude may be “let’s not take any more chances, just sting,” Sajesh says.

Both hives showed shimmering that disappeared completely when bees were given the smallest objects. In this case, a circle of four centimeters in circumference. This suggests that ripples can only be triggered by objects of a certain size.

Shimmering strength did not wane even when the bees were exposed to the artificial setup repeatedly, perhaps because it’s advantageous to stay vigilant against predators like hornets that make persistent attacks.

It is unknown how the bees perceive the objects in the study. “They could be actually seeing this object moving, or they could just be responding to a reduction in their visual field,” Sajesh says.

Researchers plan to investigate this question further. They also plan to use LED screens to alter the background colors, patterns, object shapes, and pattern to see what kind of motions the bees are most interested in.