Honeybees tell time without taking clocks or the sun into account.
Humans, along with most living organisms, have built-in clocks that tell us when to wake up, go to sleep, and so much more. This is tied in with our survival behaviors.
Scientists have known that honeybees use light to tell time. Now new details are emerging that reveal even more about honeybee circadian rhythms, and scientists are literally ‘buzzing’ about it all.
Since bees are responsible for one of every three bites of food that we eat, this is something we should know more about! Like blueberries and cherries, that are 90% dependent on honeybees for pollination.
As it turns out, a blend of laboratory and live experiments indicate that these precious insects also use temperature fluctuations inside their dimly lit or dark hives to know when to forage, or when to even do their famous waggle dance to ‘talk’ to their hive-mates. Studying honeybee behavior inside simulated hives showed researchers how bees shift their daily routines, or circadian clocks, with the temperature.
What will this mean in the coming years, with so much talk about climate change? Average global temperatures are expected to rise and that will bring more extreme weather events.
Summer and winter weather is becoming more extreme all the time. Researchers believe that these bees will face challenges since they operate within a comfortable temperature zone. If it gets too cold their wings can shrivel up, and if it gets too hot their brood can die off. Maintaining activities that keep them and the plants and crops they forage healthy and vibrant could become a real issue.
This 10:47-minute video by The BioClock Studio is fascinating and educational:
On-the-ground study was done in Gurabo, Puerto Rico, although scientists from Vanderbilt University in Tennessee, Brandeis University in Massachusetts, University of Puerto Rico Rio Piedras, University of Pittsburgh, and East Tennessee State University were all contributors.
Study co-author Manuel Giannoni-Guzmán, a postdoctoral scholar in biological sciences at Vanderbilt University, cautions that further studies are needed, but that extreme hot and cold weather could go beyond where bees can adjust and compensate, and this could lead to losses in the bee populations which could impact crops that rely on honeybees for their pollination.
The recent unexpected freezing ice storm in Texas is an example of how honeybees had to struggle to survive. You can see a blog post we wrote about it recently. The bees getting ready to forage may not have understood that they needed to conserve their energy to heat the hive. In the opposite extreme, on a 100-degrees Farenheit day, bees must expend lots of energy to keep the colony cool. According to Giannoni-Guzmán, these types of events will influence colony health or lead to possible colony collapse.
Findings were posted on May 16, 2021 in a non-peer reviewed preprint. The study will be published in the journal Annals of the Entomological Society of America.
In 2012 and 2014 the team first measured temperatures and light inside natural honeybee hives every 30 minutes in Gurabo, Puerto Rico. The average highs and lows were about 84 degrees and 64 degrees Fahrenheit. Researchers noted the temperature changed up to 7 degrees in a day.
To evaluate if bee behavior changes with temperature, the team placed some bees in simulated natural hives in total darkness and exposed them to temperature cycles observed in nature. Six days later, scientists shifted the temperature cycle by 6 hours and watched to see how the bees reacted. Researchers were surprised at the results. Roughly 51% changed behavior with the temperature, and among them, 56% made gradual alterations while 44% made abrupt changes.
Honeybees are most active in spring and summer. They slow down in autumn and withdraw into their hives in winter. They change their activities as the seasons progress. The times at which hive chores like cleaning, foraging, raising baby bees, are normally performed, could explain the variations in responses to temperature inside hives.
According to Giannoni-Guzmán, scientists observed a shift in the activity of some of the bees that matched the 6-hour shift in the temperature cycle.
Not just temperature, but other factors may also account for influencing the honeybees’ internal clocks. The researchers say humidity also fluctuates similarly in a 24-hour period.
Are these external oscillations capable of entraining the inner clock of bees? According to the study, this is a subject for future research.
Giannoni-Guzmán says the research team is interested to see how important this research is in winter weather in Tennessee, when bees rarely leave their hives. They are also interested to see how their findings apply to temperate regions with a greater degree of temperature variability across the year.