Bees benefit from coffee buzz

Most of us are familiar with that morning coffee buzz caffeine-hit– and need it to get started on our working day. But as it turns out, bees benefit from a coffee buzz too, with the chemical shown to boost their productivity and improve their recognition of the most profitable flowers, according to a new study in the journal Current Biology.

The research builds on previous studies that have found that not only do bees selectively favour flowers with naturally occurring caffeine in them, but that this caffeine may actually improve their memory function.

“When you give bees caffeine, they don’t do anything like fly in loops, but do seem to be more motivated and more efficient,” says Sarah Arnold, a researcher at the Natural Resources Institute (NRI) of the University of Greenwich, UK. “We wanted to see if providing caffeine would help their brains create a positive association between a certain flower odour and a sugar reward.”

As it turns out, bees don’t have an easy time finding the most profitable nectar out in the wild. “It’s really quite a challenging environment out there for bumble bees because they don’t have extraordinarily sharp vision at long range,” Arnold says. “They need to rely on a lot of cues, such as their sense of smell, to find good flowers.”

Read more: Caffeinated flowers give bees a buzz

As described, while previous studies have shown that bees become faithful customers at caffeinated flowers, boosting their ability to remember those plants, but in those experiments, the researchers say, it’s hard to tell whether the bees simply return because they crave the caffeine, or whether it boosts their memory function overall.

To tease this conundrum apart, Arnold and her team gave the bees caffeine at the nest, whilst they learned to associate a specific smell – a synthetic odour that mimics strawberry flowers – with a sugar solution. Afterwards, when sent out to forage, the bees that found the strawberry-scented flowers would be rewarded with a sugary, decaffeinated nectar.

Co-author Jan-Hendrik Dudenhöffer divided 86 untrained bumblebees into three groups. Group 1 received the strawberry odour and caffeinated solution, group 2 received the strawberry odour and a sugar solution (so they lacked the caffeine boost, but were exposed to the association), and group 3 received the sugar solution without any associated scent. Then they were set loose in a controlled area with robotic flowers that emitted either the strawberry odour or other distracting smells.

Based on four repeats of the trial, 70% of the caffeinated bees visited the strawberry flowers first, whereas 60% of the bees given the odour and sugar without caffeine did so. Of the bees given only sugar, 44% chose the strawberry flowers first. While it may seem a small margin, it represents a statistically significant difference in behaviour between the groups.

The find is important because some farmers – for example, strawberry growers – invest in commercial bumblebees in droves each year, but they likely lose some of the bees’ business because the critters are distracted by nearby wildflowers. By teaching the bees to prefer the crop with caffeine, farmers may improve their cost efficiency when investing in bees.

Notably, though, the preference didn’t endure: once the caffeinated bees figured out they could get sugar from all the other types of flower, they resumed business as usual.

“This is something we could have anticipated, because the bees got sugar no matter if they visited the target flower or the distractor flower,” says Arnold. “In some ways, they were unlearning just as fast as they were learning.”

The researchers also noted that caffeine subtly improved the bees’ “handling speed” – the number of flowers they visited in a given time period. This suggests, they argue, that caffeine may to some extent improve motor learning skills.

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