Heavy Loads Of Pollen May Shift Flight Plans Of The Bumblebee : The Salt Foraging bumblebees can pick up nearly half their weight in pollen before heading home to the hive, research shows. All that weight tucked into hollows on their hind legs can complicate flying.

Heavy Loads Of Pollen May Shift Flight Plans Of The Bumblebee

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If you've been outside today, maybe you heard this summertime sound.


BLOCK: A bumblebee gathering pollen from a flower. Bumblebees routinely haul around heavy loads of pollen or nectar. NPR's Nell Greenfieldboyce reports that scientists recently investigated how the flight of a bumblebee is affected by that.

NELL GREENFIELDBOYCE, BYLINE: Despite what you may have heard, bumblebees do not defy the laws of physics when they fly. Decades ago, this idea entered popular culture maybe because engineers could not explain bumblebee flight using models developed for fixed-wing aircraft like airplanes.

ANDREW MOUNTCASTLE: But of course, bumblebees fly in a very different way than airplanes do. They flap their wings, and their wings bend and twist as they flap them.

GREENFIELDBOYCE: Andrew Mountcastle is a biologist at Harvard University. He says bumblebees are very good at flying in all kinds of weather, and they do it while loaded with cargo.

MOUNTCASTLE: And what might be surprising to many people is just how much load they're able to carry. Bumblebees are basically aerial tankers.

GREENFIELDBOYCE: They have a specialized pouch in their abdomen to store nectar - a lot of nectar. They can double their body weight. They pack pollen into storage bins on their hind legs. Mountcastle and his colleagues wanted to understand how a bee's flight is affected by what it's carrying. So first, they went online and ordered a hive of bumblebees.

MOUNTCASTLE: And it comes packaged in a nice box, and it always excites the FedEx guy when he drops off a buzzing hive at your door.

GREENFIELDBOYCE: They trained the bumblebees to fly through a wind tunnel by rewarding them with nectar from an artificial flower at the other end. Next, to start the experiment, they weighed the bumblebees down.

MOUNTCASTLE: We use artificial weights in the form of really, really small steel ball bearings.

GREENFIELDBOYCE: They either glued them on the legs to simulate a pollen load or on the abdomen to simulate a load of nectar. They sent the bees flying through the wind tunnel again under various wind conditions and filmed them with high-speed video. When they analyzed the video, they found that the type of cargo did make a difference. In turbulent wind conditions, bees were more stable when they carried weight on their legs like they do when gathering pollen.

MOUNTCASTLE: Conversely, though, carrying a pollen load comes with a downside when the goal is maneuverability.

GREENFIELDBOYCE: In calm air, bees with heavy legs were less nimble than bees with full bellies. The researchers describe their work in the proceedings of the National Academy of Sciences. Now they want to know, do bumblebees decide to gather pollen or nectar depending on the wind conditions?

SRIDHAR RAVI: This is something which would be the sort of next question we ought to tackle.

GREENFIELDBOYCE: Sridhar Ravi of RMIT University in Australia also worked on this study. He says bumblebees are very clever.

RAVI: They can solve problems. We have had them fly through obstacle courses, mazes, and they just come out trumps. And you just have to sort of wonder, oh, my god, they are so smart, you know?

GREENFIELDBOYCE: He says experiments are in the works to see if the weather affects what bumblebees bring home. Nell Greenfieldboyce, NPR News.

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