flying frog ...

the origin of novel phenotypes has challenged evoluionary biologists since the time of darwin. darwin's theory of evolution provides an explanation for how natural selection eliminates the less fit phenotypes, but leaves open the question of how novel phenotypes arise !

rhacophorus malabaricus is a large-sized tree frog endemic to the western ghats of india. inhabits evergreen, and semi-evergreen forests and builds arboreal foam nests. gliding tree frogs have features such as enlarged, extensively webbed hands and feet with adhesive discs, skin flaps on elbows and ankles. these frogs use gliding to descend from the canopy down to mating sites over temporary pools on the rainforest floor and to escape from predators.

aerodynamic stability and maneuverability

the motion an animal experiences during flight is marked by transitory oscillations (phugoid mode, short-period mode, Dutch-roll mode and spiral mode) superimposed over translation along a flight path. In addition, the flight path may be changing as a result of postural changes by the animal.

maneuverability is the ability of a gliding animal to accelerate and change its flight path. a gliding animal is capable of accelerating linearly and rotationally. turning maneuvers are accomplished by rotations about the glider's center of mass that in turn alter the aerodynamic forces acting on the glider. maneuverability depends on the magnitude of the aerodynamic forces the frog can generate as well as the frog's aerodynamic stability.

this rotation can be resolved into rotations about three orthogonal axes, pitch, roll and yaw. the origin of the axes is fixed to the animal's center of mass, and the axes themselves are fixed to the animal; the axes translate and rotate as the animal translates and rotates. (A) rotation about the cranial-caudal axis is termed roll angle, rolling rotates the animal's right side up or down. (B) rotation about a dorso-ventral axis is termed yaw angle, yawing rotates the animal's snout to the left or right. (C) rotation about a lateral axis is termed angle of attack, pitching rotates the animal's snout up or down. grey arrows indicate the directions of the indicated torques.

tree frogs maneuvered in the tilted wind-tunnel using two different turning mechanisms: a banked turn (the frog rolls into the turn) and a crabbed turn (the frog yaws into the turn). the maneuverability was approximately one-third of the maneuverability of a falcon.

thank u so much for your wonderfull research MICHAEL G. McCAY