Flying and Gliding Animals - Types of Aerial Locomotion

Types of Aerial Locomotion

• Falling: decreasing altitude under the force of gravity, using no adaptations to increase drag or provide lift.
• Parachuting: falling at an angle greater than 45° from the horizontal with adaptations to increase drag forces. Very small animals may be carried up by the wind. Some gliding animals may use their gliding membranes for drag rather than lift, to safely descend.
• Gliding flight: falling at an angle less than 45° from the horizontal with lift from adapted aerofoil membranes. This allows slowly falling directed horizontal movement, with streamlining to decrease drag forces for aerofoil efficiency and often with some maneuverability in air. Gliding animals have a lower aspect ratio (wing length/breadth) than true flyers.
• Flapping: moving wings for directly producing thrust. May ascend without the aid of the wind, as opposed to gliders and parachuters.
• Soaring: gliding in rising or otherwise moving air that requires specific physiological and morphological adaptations that can sustain the animal aloft without flapping its wings. The rising air is due to thermals, ridge lift or other meteorological features. Under the right conditions, soaring creates a gain of altitude without expending energy. Large wingspans are needed for efficient soaring.
• Ballooning: being carried up into the air from the aerodynamic effect on long strands of silk in the wind. Certain silk-producing arthropods, mostly small or young spiders, secrete a special light-weight gossamer silk for ballooning, sometimes traveling great distances at high altitude.

These forms of aerial locomotion are not mutually exclusive and indeed many animals will employ two or more of the methods. Two other common forms of aerial locomotion for humans that are not employed in the rest of the animal kingdom are heli-propulsion and lighter-than-air flight.