The physics of effective flying

Biologists, physicists, and engineers from Brown University in the US, have revealed the energy saving technique that bats use when flying. The researchers generated high-speed videos of bats flying by placing markers on their wings and filming them at 1000 frames-per-second. The videos reveal that, as bats raise their wings during flight, they fold them in towards their body instead of keeping them outstretched.

When analysing the physics of flight researchers usually look at factors such as the aerodynamics of the wings. However, this time the mass of the wings and how much energy was required to move them was also considered. The group performed detailed mathematical analysis and found that, by folding their wings in, bats save roughly 35% of the energy required to fly with their wings fully extended.

This energy-saving technique is important because bats' wings are very muscular and heavy relative to their size. The study suggests that bats use the flexibility of their wings to compensate for the increased mass, as folding their wings influences a number of other factors too. For example, the mass of the wings is closer to the bat's body when they are folded in, which reduces the moment and makes it easier for the bat to lift the wing.

Due to the fact that this flying technique reduces the energy cost to the bat, it may be possible that it is an evolutionary adaptation.

Glossary

Moment

Moment refers to the moment of the force. Moment is equal to the distance from the pivot multiplied by the gravitational force. In this case, the distance from the pivot is the distance from the shoulder joint of the bat; the gravitational force is the weight of the wing.