Bees need to think about what they drink

Bees drink to vomit. They take nectar from flowers then regurgitate it in their nests for use by others.

It’s a simple process, but new research suggests the nature of the nectar is important.

A higher sugar content makes it more appealing to drink, as well as providing more energy, but it also makes it thicker and stickier.

Now scientists at the University of Cambridge, UK, have discovered that thicker nectar takes more time and effort to regurgitate, sapping the bee’s energy.

“Nectar sugar concentration affects the speed of the bees’ foraging trips, so it influences their foraging decisions,” says Jonathan Pattrick, first author of a paper in Journal of the Royal Society Interface.

In their study, Pattrick and colleagues weighed and watched the habits of the Buff-tailed bumblebee (Bombus terrestris), which is common throughout the UK and Europe. 

The bees foraged on sugar solutions of three different concentrations in the university’s Bee Lab, then returned to a nest, where the researchers watched how long it took them to vomit. 

“For low strength nectar, bees had a quick vomit that only lasted a few seconds then were back out and foraging again, but for really thick nectar they took ages to vomit, sometimes straining for nearly a minute,” says Pattrick.

At any sugar concentration, bees regurgitate nectar more quickly than they initially drink it, but as the concentration and stickiness increase, the rate of regurgitation decreases more quickly than the rate of drinking. 

“It’s hard to drink a thick, sticky liquid, but imagine trying to spit it out again through a straw: that would be even harder,” says Pattrick. “At a certain sugar concentration, the energy gain versus energy loss is optimised for nectar feeders.”

The researchers say the perfect nectar sugar concentration for the highest energy intake depends on the species drinking it, because different species feed in different ways. 

Bumblebees and honeybees feed by dipping their tongue repeatedly into the nectar, then regurgitate by forcing the nectar back up through a tube – much like a human being sick. 

However, other species, such as Orchid Bees, suck the nectar up rather than lapping it, so struggle even more when nectar is highly concentrated. 

This influences nectar preference and the plants visited by different species.

And that knowledge, the researchers suggest, should inform breeding efforts to make crops more attractive to pollinators.