Wildlife – Aerodynamic Nocturnal Gliders

‘Gliding Squirrels’ popularly known as ‘flying squirrels’ occur in several parts of the globe. Spread across, north America to Europe and to Asia, these species are elegant as well as aerodynamic in nature. Though they are popularly known as ‘flying squirrels’, they infact ‘glide’ and do not ‘fly’. South and Southeast Asia are hub to array of gliding squirrels. In India alone, atleast 18 species of gliding squirrels occur. In the Indian state of Arunachal Pradesh alone, 14 species were recorded in a study. Among them, Namdapha Gliding Squirrel is the most threatened and elusive species. These nocturnal gliders use canopy for movement and glide upto several hundred meters even. Among the several species that are found in India, Woolly gliding squirrel is the only species that occurs in high altitudinal rocky cliffs and rest all are found in the tree forests. Among these gliding squirrels, some of them are very small in size viz., particolored gliding squirrel which could be of a size of a house rat and some species like Red giant gliding squirrel can be as big as 3.5 feet in length including its tail.

Gliding squirrels are kind of elusive species as they are active in night and thus are called ‘nocturnal’ in habit. They usually get active at dusk and then go back to their nest/resting sites before sunrise. They can see in the night as they are equipped with large eyes and large pupils that can open wide in low light. Also, a special reflective membrane called tapetum lucidum lies behind the eye which reflects light that has passed through the retina, acting as an additional reflective lens which helps more light to enter. If the light is not absorbed upon reflection it is reflected back out of the eye and is the reason why the eyes of nocturnal mammals appear to “glow” in the night. They use the height of the trees to make longer glides soon after emerging from the nesting/resting tree. The gliding event is usually, the species moving up to the top or edge of the canopy from where it marks the tree to which it needs to glide (generally the landing tree should have a clear trunk). They use the wind and steer through the canopy using their tails (as radar) which are covered with thick hair. These species nest in tall tree hollows and if they sense any competition with other cavity nesting birds, they make leaf nests. Their diet is a combination of leaf, fruit, flower, bark and sap. Though they are considered as fulivorous (leaf eating), they switch to frugivory (fruit eating) based on the availability of the fruits and based on season. They are mostly solitary in nature, but are usually found in pairs or small groups during breeding season and they communicate with each other using monotonous repeated wail’s which can be heard upto several hundred meters in forests. They usually mate either once or twice in a year.

A red giant gliding squirrel (larger species) from Namdapha National Park in Arunachal Pradesh, India.

They play a major role as pollinators, as prey, as seed dispersers as well as seed predators. However, we are yet to understand their complete role in the ecosystems. Habitat loss due to expanding agriculture, shifting cultivation are one of the threats to the species. These gliders require tall and mature trees to live, if the trees are lost, they will disappear as they have no other place to live. Apart, they are hunted as a part of bushmeat purposes. And other developmental projects like linear infrastructure (roads) and tall fencing, powerlines are also responsible for their death. There is a need for us to conserve these unique, elegant nocturnal gliders as they indirectly help humans in growing and maintaining forests ecosystems.

Dr. Murali Krishna Chatakonda

(Author is an Assistant Professor at Amity)

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