The world’s gliding mammals are an extraordinary group of animals that have the ability to glide from tree to tree with seemingly effortless grace. There are more than 60 species of gliding mammals including the flying squirrels from Europe and North America, the scaly-tailed flying squirrels from central Africa and the gliding possums of Australia and New Guinea.
The world’s gliding mammals are a diverse group of animals that have the unusual ability to glide from tree to tree with seemingly little effort. They do this by launching from the upper branches or trunk of a tree and spreading out their specially adapted gliding membranes, which stretch from the sides of their body between their fore and hind limbs. This allows them to glide silently through the night air for a considerable distance — some species are able to glide for more than 100 metres. During these glides they can twist and turn around obstacles to make a safe landing on a target tree without the need to come to the ground.
There are currently 65 recognised species of gliding mammals from six different families. There are three families of gliding marsupials that live in Australia, New Guinea and surrounding islands. These families include the Feathertail Glider (Family Acrobatidae), the gliding possums of the genus Petaurus (Family Petauridae), and the Greater Glider (Family Pseudocheiridae). However, by far the greatest diversity of gliding mammals occurs in the Order Rodentia, where they are represented by the flying squirrels belonging to the Family Sciuridae and the unrelated scaly-tailed flying squirrels of the Family Anomaluridae. The Sciuridae includes all the tree and ground squirrels with some 51 genera and 278 species in total. Of these, the flying squirrels comprise 15 genera and 49 species, and are found throughout Asia, Europe and North America. The family of scaly-tailed flying squirrels that live in central and western Africa has seven species, although one species does not glide. Gliding reaches its most spectacular and efficient in the two species of colugos, also known as flying lemurs, of the Order Dermoptera, which occur throughout South-East Asia.
Animals that glide between trees descend at an angle less than 45° to the horizontal, while those that parachute descend at an angle greater than 45°. Gliding is achieved by deflecting air flowing past a well-developed gliding membrane, or patagium, on each side of the body. These membranes convert the animal’s body into an effective airfoil, allowing it to travel the greatest possible horizontal distance with the minimum loss of height. The flying squirrels and scaly-tailed flying squirrels even have special cartilaginous spurs that extend either from the wrist, or elbow respectively, to help support their gliding membranes.
In addition to mammals and birds, gliding has evolved independently as a form of locomotion in several groups of arboreal and even aquatic vertebrates. These include flying fish of the Family Exocoetidae (from which we get the name Exocet missile), which have either two enlarged pectoral fins or even four enlarged fins (both pectoral and pelvic) to act as wings. These modifications allow them to make glides of over 60 metres above the water to escape from predators and potentially save energy.
The flying snakes of the genus Chrysopelea (and possibly the genus Dendrelaphis) of the Family Colubridae have developed a form of gliding by flattening and broadening their body like a ribbon through the use of hinged ventral scales, and by drawing in the belly so that it forms a concave surface when they leap out of trees.
Flying geckos of the genus Ptychozoon, fringed geckos of the genus Luperosaurus, and house geckos of the genus Cosymbotus (Family Gekkonidae) jump from tree to tree aided by webbed feet, flaps or folds of skin along the lateral body wall, and dorso-ventrally flattened tails that increase their horizontal surface area. Among the reptiles, however, the development of gliding reaches its pinnacle within the gliding lizards of the genus Draco (Family Agamidae). The ribs of these species are greatly elongated to create a large gliding surface, which folds against the sides of the body when not in use. When these lizards jump from a tree, they spread their ribs to stretch out the gliding membrane and can make glides of over 30 metres.
A variety species of frogs from three families are known to parachute or potentially glide. These include various species of flying frogs from the genus Rhacophorus and some of the whipping frogs of the genus Polypedates (Family Rhacophoridae) from South-East Asia. Several species of South American frogs of the Family Hylidae have extensive webbing including the Gliding Leaf Frog (Agalychnis spurrelli), Fringe-limbed Treefrog (Hyla miliaria) and Rabb’s Fringelimbed Treefrog (Ecnomiohyla rabborum) and may also have the ability to glide.
Various other frogs are known or thought to undertake controlled aerial descent including Hyperolius castaneus (Family Hyperoliidae) that occurs in tropical and subtropical forests of central Africa. The most developed frogs typically possess enlarged toes that have well developed webbing between them, with some species from the old world even having flaps of skin on the forelimbs and hind limbs to help trap air during descent. While the frogs with the most highly developed webbing may be able to truly glide, most species are more accurately described as parachuters. Nonetheless, the aerial control of these frogs is often so well developed that they can even make banked 180° turns.