Honeybees tell time without clocks or sun, study says. It may be bad news for your diet

Nearly all living organisms from humans to microscopic fungi have an internal clock that signals when it’s time to wake up and go to sleep, among other complex behaviors needed to survive.

Now, scientists are buzzing over newly emerged details about the circadian rhythms of honeybees — those busy bodies responsible for about one of every three bites of food you eat.

It’s well known that honeybees use light to tell time, but a mixture of laboratory and real-world experiments revealed the insects also use temperature fluctuations inside their dark hives to understand when it’s time to hunt for food, mate or even whip out their fancy dance moves to send important messages to others.

By studying forager honeybee behavior inside simulated hives, a team of researchers learned the bees shifted their daily routines, or circadian clocks, with the temperature. But with average global temperatures expected to climb over the years, bringing along with it more extreme weather events, how could this time-telling tool affect honeybees?

Researchers say the critters are bound to face challenges in “maintaining the activities that keep them and the agriculture they support healthy and vibrant” — temperatures too low can shrivel their wings and temperatures too high can kill off brood.

“While studies are still needed to answer this question, extreme winter and summer weather could reach a point beyond what bees could compensate, leading to losses in the bee populations,” Giannoni-Guzmán told McClatchy News in an email. “This could in turn impact crops” that rely on honeybee pollination.

Honeybees are among the most efficient pollinator species in the world, placing apples, cranberries, broccoli and many other crops on our plates, according to the American Beekeeping Federation. Some, like blueberries and cherries, are 90% dependent on honeybees, while others such as almonds have bees to thank for it all.

The findings were posted as a non-peer reviewed preprint on May 16, but a study will be published in the journal Annals of the Entomological Society of America.

“If part of the southern U.S. is hit with an unexpected snowstorm, bees getting ready to forage might not realize they need to conserve energy and heat the hive. In the event of a 100-degree day, bees will have to expend a lot of energy keeping the colony cool,” study co-author Manuel Giannoni-Guzmán, a postdoctoral scholar in biological sciences at Vanderbilt University in Tennessee, said in a statement. Researchers from Brandeis University in Massachusetts, University of Puerto Rico Rio Piedras, University of Pittsburgh and East Tennessee State University also contributed to the work.

“It is those considerations that will influence colony health or possible colony collapse,” Giannoni-Guzmán added.

The team first measured temperatures and light inside natural honeybee hives located in Gurabo, Puerto Rico, every 30 minutes between 2012 and 2014, averaging a high of about 84 degrees Fahrenheit to a low of about 64 degrees. The researchers learned the temperature changes as much as 7 degrees in one day.

To determine if bee behavior changes with temperature, the team simulated natural hives in a lab, placing them in complete darkness while exposing the insects to temperature cycles observed in the wild. After six days, the researchers shifted the temperature cycle by six hours to see how the bees reacted.

About 51% of the honeybees changed their behavior along with the temperature. Among them, 56% made gradual alterations while 44% made abrupt ones, to the researchers’ surprise.

“In general honeybees will change their activity levels as the seasons progress. They are more active in spring and summer months, come fall their activity begins to taper,” Giannoni-Guzmán told McClatchy News. “We observed a shift in the activity of some bees that matched the six-hour shift in the temperature cycle.”

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The many jobs honeybees take up to support their hive, such as cleaning, raising young or foraging for food, are thought to be determined by a mixture of genetics and hormones. The researchers speculate that these different tasks, and the times they are usually performed, could explain the variations in responses to temperature inside hives.

Other factors besides temperature may be able to influence honeybees’ internal clocks, too, the researchers said, such as humidity, which they noticed fluctuates similarly in a 24-hour period.

“However, whether these oscillations are capable of entraining the clock of bees remains a subject of future research,” they wrote in the study.

“We want to see how important this research is come winter in Tennessee, when bees aren’t leaving the hive as much,” Giannoni-Guzmán said. “We will be interested to see how our findings apply to temperate regions where there is a greater degree of temperature variability across the year.”