Bats actively modulate membrane compliance to control camber and reduce drag

Area of Science:

• Biomechanics
• Animal Flight
• Aerodynamics

Background:

• Bat wing skin is highly flexible and changes shape during flight.
• Small muscles, plagiopatagiales proprii, are in the armwing membrane and activate during flight.
• These muscles are hypothesized to control membrane tension.

Purpose of the Study:

• To investigate the function of plagiopatagiales proprii in bat flight.
• To understand how these muscles modulate wing membrane tension and aeroelastic interactions.
• To determine the impact of muscle paralysis on flight performance and kinematics.

Main Methods:

• Used Jamaican fruit bats (Artibeus jamaicensis).
• Paralyzed plagiopatagiales proprii muscles using botulinum toxin.
• Analyzed changes in preferred flight speed, low-speed flight capability, and compensatory kinematics.

Main Results:

• Paralysis of plagiopatagiales proprii decreased preferred flight speed.
• Bats were unable to fly at very low speeds after muscle paralysis.
• Increased armwing camber and compensatory kinematic changes (e.g., increased downstroke angle) were observed.
• These changes suggest increased drag and flight power costs.

Conclusions:

• Plagiopatagiales proprii muscles are essential for controlling bat wing camber during flight.
• These muscles enhance flight efficiency across a broad range of flight speeds.
• Jamaican fruit bats likely utilize these muscles continuously during sustained flight for optimal performance.