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.
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 published in the journal
Biology Letters.
“So the roughly 60 per cent decline in air density has to be
matched by a 60 per cent increase in force production – a
remarkable feat when you also consider that they are doing this in
such low oxygen,” Professor 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.
