Sleepy honeybees dance sloppily
Fatigue affects bees’ ability to communicate
Douglas Main • March 18, 2011
Sleep-deprived honeybees can’t communicate as well as their well-rested sisters, according a study published recently in the journal Proceedings of the National Academy of Sciences.
“When deprived of sleep, foraging bees provided less precise information to their sisters in the hive,” said University of Texas researcher Barrett Klein, the study’s lead author.
As social animals, bees must be able to communicate effectively to one another, and they have an uncanny ability to do so. It’s vital for honeybees to tell her sisters (all worker bees are female and closely related) where to find choice flowers. They do this via their famous waggle-dance. Bees sleep at night like humans, and bees that forage – the most advanced job for a worker – are very particular about getting regular sleep. Klein, who has always been fascinated by bees and the process of sleeping and dreaming, hypothesized that disrupting bees’ sleep might affect their communication skills.
“When deprived of sleep, humans have a reduced ability to perform a variety of tasks,” Klein said. “One of the most important effects is lack of ability to communicate with other humans. I was excited to see if honeybees suffered some sort of analogous breakdown in their communication.” And they do.
Klein isolated 50 bees at a research station, and then glued tiny metal dots, or “backpacks” onto their fuzzy dorsal mesosomas (a.k.a. their backs). Half were steel and half were non-magnetic copper. He then ran a magnet-filled contraption (called the “insominator”) back and forth across the hive several times during the night, jostling the steel-clad bees awake and limiting their sleep. The next day, he filmed each of the 50 bees’ waggle-dances, which are used by foragers to tell their hive-mates where to find food. After using a computer program to calculate the angle of the dance, used to signal the pollen or nectar’s location, Klein found that the tired bees were less precise in communicating than their well-rested brass-backed sisters.
When bees do their intricate waggle-dance, the angle they take from the vertical plane when dancing is the same as the angle between the sun and the food source upon exiting the hive. For example, If the flowers are 45 degrees to the right of the sun (upon exiting the hive), the dance will be oriented 45 degrees to right of vertical, Klein said. Tired bees showed a wider variation in the angles of their dance than well-rested ones; in short, they were less precise. Interestingly, the dance’s repeated waggle phases, used to communicated distance, were not affected.
Bees use the earth’s magnetic field to help them find their way about, and for this reason Klein was careful to use the insominator on each side of the hive to cancel out magnetic interference. Moreover, the control (brass-clad) bees showed no impact in their signaling, suggesting that no significant magnetic tinkering was afoot. However, another bee researcher, Randolf Menzel, said Klein’s use of magnets might “disturb the bees’ magnetic orientation which in turn may lead to less precise directional components in dance communication. Thus the interpretation in this paper may not be as straightforward as the authors wish to see it,” said Menzel, who works at the Free University of Berlin. But he did add that it was a very nice publication from one of the “best labs on honeybee behavior.”
So, what might this tell us about humans and their ability to communicate when sleepy? Bee researcher Gene Robinson at the University of Illinois (who was not involved in Klein’s research) said that many of the genes controlling circadian rhythms and communication in bees are present and active in humans. “We’re largely playing with same deck of cards,” Robinson said. “That leads to the notion that what is learned in animal models can be used to understand humans.” Of course, humans are more complicated. “It’s not like bees are small humans,” he said. “There’s a great deal of difference. But if one properly appreciates the difference, one can use the deck of cards concept to build a connection between bees and humans.”