Lifestyle

How do you cheer up a bumblebee? Try sugar.

Jens Meyer/AP/File

Like many kids, I used to lie in the grass and watch bumblebees harvesting pollen from the clover. Unlike many other bees, these big, furry bees were so gentle I could let them crawl across my palm without fear of getting stung. I loved to select one bumble to follow around the yard as she buzzed from clover to rose, rose to snapdragon, sipping nectar from her pointy black tongue and collecting pollen on her fuzzy black and yellow coat, later to groom it off to carry home in “pollen baskets” on her rear legs. Though our parents may have chuckled at our beliefs, I’m sure lots of kids, like me, reported that our insect friends were cheerful and smart.

As it turns out, we were right.

Advertisement

Two separate studies published this fall report that bumblebees show emotions, solve problems, and will teach others how to solve problems, too.

“Even insects express anger, terror, jealousy and love,” Charles Darwin wrote in “The Expression of the Emotions in Man and Animals.” But in the ensuing 150 years, his views fell so out of favor that few scientists even tried to look for thinking or feeling in tiny, invertebrate animals — until now.

Get The Weekender in your inbox:
The Globe's top picks for what to see and do each weekend, in Boston and beyond.
Thank you for signing up! Sign up for more newsletters here

It’s difficult to study something as private as an emotion in a creature as different from us as a bumblebee. Unlike our dogs and cats, they have little reason to communicate with us. So neuroethologist Clint Perry at Queen Mary University in London came up with an ingenious experiment, published in Sept. 30’s Science. His research team trained 24 bees to enter a plastic tunnel when a treat was promised. When marked with a blue card, the end of the tunnel offered tasty sugar water. A green sign meant none.

But what about an aquamarine sign? The bumbles were confused, just as you or I might be. Was it green or blue? They wandered around, not knowing what to do. Then the researchers gave half the bees a dose of cheer: a surprise treat of a drop of sugar water. Like people in a good mood, they then became more optimistic: they entered the ambiguous tunnel, encouraged to hope for the best. Those who had no sugar water spent just as much energy dithering around, but didn’t take a chance that the tunnel would be a good bet. This suggests that the metabolic effects of the sugar wasn’t responsible for the bees’ behavior — but the boost in mood was. Who doesn’t cheer up after a sweet treat?

Here’s the clincher: The effect of the sugar water disappeared when the bees were given a drug that blocks the receptors for the brain chemical dopamine — the neurotransmitter associated with pleasure and motivation in humans and animals. Bees possess the same neurotransmitters as humans do. Why shouldn’t they have similar emotions?

Advertisement

In another experiment at the same university and published in Plos One in October, researcher Lars Chittka watched bumblebees figure out how to use string to retrieve a snack. Artificial flowers filled with sugar water were placed under Plexiglass and tied to a string sticking out from under the plastic. Eventually, a particularly insightful bee would figure out that by yanking the string with their front legs, they could retrieve the flower and sip the liquid.

What happened when Chittka allowed unsuccessful bees to watch the insightful one was even more exciting. Most of them learned the new behavior by watching — and when these student bees were introduced to new colonies who had never seen the string-pulling, the learned behavior spread from bee to bee. Soon almost everyone was pulling the strings to get to the sugar water.

Sadly, just as scientists and adults are starting to appreciate the fuzzy, gentle bees we loved as children, bumblebee populations are crashing across the United States and Europe. In September, the US Fish and Wildlife Service proposed listing the rusty patched bumblebee, once common throughout the Northeast and Midwest, as federally endangered. It’s lost 95 percent of its population since 1990, and now only lives in 12 states, including Maine and Massachusetts.

The rusty patched is not the only one of the 50 species of bumblebee in the US and 250 species of bumblebee worldwide to be threatened — at least four others are in serious decline. (The rusty patched is just the one whose decline is best-documented.) Pesticides, global climate change, loss of favorite wild food plants, and a fungal gut disease imported from Europe are all implicated.

Invertebrate ecologist Timothy Hatten, a consultant and adjunct faculty member at University of Idaho, is among the researchers trying to help save the bumblebees, but his findings have only deepened the mystery. His team surveyed bumblebees along Canadian highways of British Columbia and Yukon territories and found many bees carrying the European fungus called Nosema bombi. Yet mysteriously, despite the infection, in these northerly locations, the bees seemed to be doing fine.

Bumblebees deserve our protection. “Bumblebees are among the most important of all pollinators,” says Hatten. Unlike honeybees, who are mostly Italian imports, our native bumblebees forage throughout the growing season, and their thick pile coats render them especially well adapted to cool climes like ours in New England. If we lose them, we forfeit an essential link in our food chain.

But perhaps just as tragic would be the loss of a childhood icon — a friendly, fuzzy bee who enticed so many of our young selves to explore and observe the natural world.

Sy Montgomery is the author of more than 20 books, including “The Soul of an Octopus.” Send your questions about animals to syandlizletters@gmail.com.
Loading comments...
Real journalists. Real journalism. Subscribe to The Boston Globe today.