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Sunday, 9 February 2014

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Bumblebee can fly over Mount Everest, say scientists

The flight of the bumblebee - once thought to be aerodynamically impossible - has proven to be even more scientifically astounding than previously believed following a study showing how the humble insect is able to fly high enough to pass over Mount Everest.

Researchers have discovered that a species of Chinese bumblebee is still capable of flight when the air pressure falls to a level equivalent to an altitude of 9,000 metres - more than enough to fly over the 8,848-metre-high peak of the greatest mountain in the world. Video recordings of bumblebees flying in a barometric chamber where the air pressure is allowed to fall to levels that would suffocate most other animals show that the bees continue to fly by altering the angle of their wings to increase their amplitude as they flap back and forth.


Hungry bumblebees travel more than a mile to find food

Scientists found that even when the concentrations of oxygen reached perilously low levels as the density of the air fell inside the chamber, the bumblebees still managed active flight in conditions equivalent to the thin air on top of the highest mountain range.

The bumblebees effectively increased the force produced by their flapping wings to compensate for the thinness of the air, rather than increasing the wing-beat rate, said Michael Dillon of the University of Wyoming, who led the study.

"So the roughly 60 percent decline in air density has to be matched by a 60 percent increase in force production - a remarkable feat when you also consider that they are doing this in such low oxygen," Prof Dillon said.

"A hovering bumblebee has an oxygen demand that is roughly 15 to 20 times that of an elite athlete, yet in our experiments they are meeting this demand in spite of a greatly reduced supply - the partial pressure of oxygen is less than a third of sea-level values," he said.

The experimenters captured wild bumblebees belonging to the species Bombus impetuosus which forages for nectar and pollen in the mountains near Rilong in Sichuan province of China.

Within 10 minutes of being captured they were placed in a barometric chamber and their flight filmed as the air pressure was slowly lowered.

The images revealed that the bees increased the angular velocity of their wings by increasing the amplitude of each wing stroke while maintaining a constant wing-beat frequency. The flight angle of the bee increased as a result of the shift, the researchers found.

"This extreme flight performance is likely to be biologically relevant in other contexts. For example, bumblebees fill up on nectar and pollen so that they can deliver these resources back to the hive and feed developing young," Prof Dillon said.

"Flying with a large load is much more challenging than flying empty.

-The Independent

Hungry bumblebees travel more than a mile to find food

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