How animals glide: from trajectory to morphology

Abstract

Animals that glide produce aerodynamic forces that enable transit through the air in both arboreal and aquatic environments. The relative ease of gliding compared with flapping flight has led to a large diversity of taxa that have evolved some degree of flight capability. Glide paths are curved, reflecting the changing forces on the animal as it progresses through its aerial trajectory. These changing forces can be under control of the glider, which uses specific aspects of anatomy to modulate lift, drag, and rotational moments on the body. However, gliders share no single anatomical or behavioral feature, and some species are unspecialized for gliding, producing aerodynamic forces using posture and orientation alone. Animals use gliding in a broad range of ecological roles, suggesting that multiple performance metrics are relevant for consideration, but we are only beginning to understand how gliders produce and control their flight from takeoff to landing. In this review, we focus on the physical aspects of how glide trajectories are produced, and additionally discuss the range of morphologies and postures that are used to control aerial movements across the broad diversity of animal gliders.

How lizards fly: A novel type of wing in animals

“…Apart from few groups of gliding or parachuting animals that use only their flattened bodies and unmodified, outstretched limbs to generate lift and drag forces [2,21,22], all other groups of flying and gliding animals have developed enlarged aerodynamic surfaces that are permanently attached to the skeletal and muscular elements that control them [2,3,19]. The enlarged aerodynamic surfaces of vertebrates are mostly found on modified limbs or fins (Fig 6).…”

“…A number of vertebrates and invertebrates are known to perform gliding flights [1][2][3]. Flying Lizards of the agamid genus Draco are the most specialized and best-studied gliding reptiles [2,[4][5][6].…”

“…This assumption was promulgated about 300 years ago, when the first preserved specimens were brought to Europe and reports of flying lizards were accompanied by drawings showing artistic interpretations of them holding their forelimbs in front of the body while "gliding" [9][10][11][12]. The patagium-associated musculature has been suspected to be used to control the direction of the glide path [1,3,[6][7][8], but it has remained unclear how the lizards are able to manoeuvre in the air [2,6].…”

“…Flying Lizards of the agamid genus Draco are the most specialized and best-studied gliding reptiles [2,[4][5][6]. Their patagium is supported by five to seven greatly elongated thoracic ribs that are spread by specialized iliocostalis and intercostal muscles [1,3,4,[6][7][8].…”

Into rude air: hummingbird flight performance in variable aerial environments

“…Such aspects of performance are much less studied relative to steadystate horizontal flight or hovering, but are essential to flight and survival in the natural world. Animal flight manoeuvrability, more generally, is a topic under intense current investigation [4][5][6][7][8], but specific aspects of axial and torsional agility used when flying in aforementioned environmental conditions remain largely unstudied. Although of obvious biological importance, such capacities can also be relevant to the survivability of microair vehicles in comparable environments.…”