Namdapha National Park is a dream destination for birdwatchers from India and abroad. Lying in the easternmost part of Arunachal Pradesh, bordering Myanmar, it is one of the remotest locations in India. In 2011, after crossing the rough waters of the Dihing River, I travelled to Deban, a camping location inside Namdapha National Park. I was amazed by the lush green forests, the blue skies and crystal-clear waters and was welcomed by hornbills, trogons and other bird species commonly heard only in the hill states of Northeast India.
I was in Namdapha National Park to study gibbons. Our work happened mostly in the daytime as gibbons are diurnal. An interesting incident occurred one night when I decided to explore the nightlife of these vast jungles with my co-researcher. We were scanning the canopy with spotlights around the rest house in Deban, when we saw red eyes shining, on a tree around 25 m high. The animal was busy feeding on the fruits of the Cadamba or kadam tree (Anthocephalus kadamba). It was not clear to me which animal it was due to poor lighting and the distance from us. I looked through binoculars while my colleague shed torchlight on the animal. That was the first time I saw a red giant gliding squirrel (Petaurista petaurista). Although they are common, I had rarely ventured out at night to explore the world of these amazing lesser-known animals. Sighting the gliding squirrel that night inspired me to research them further.
South and Southeast Asia are hotspots for gliding squirrel diversity, but these species are understudied. This may be because gliding squirrels are nocturnal and dwell high up in the canopy, which in these regions could go up to 30-40 m. Species like Kashmir gliding squirrel however, reside in the rocky cliffs of the western Himalayas. Though they are popularly called flying squirrels, they actually glide and do not fly.
The majestic lowland tropical forests of the Namdapha National Park form an ideal habitat for this squirrel, though they may occupy a range of forests. Their distribution extends through the western Himalayas into northern and northeast India, and on to Southeast Asia. It includes Nepal, southern China, Thailand, peninsular Malaysia, Sumatra, Java, and Borneo. They are listed as “Least Concern” on the IUCN Red List.
Though they weigh about 1.5 kg and are about one metre in length (including the tail), they are considered small mammals, falling under the group Rodentia. They are usually solitary, though they are sometimes seen in pairs or small groups (up to 8-10 individuals). In Namdapha National Park, they occupy lower elevation tropical forests up to 1,500 m. Their home range is small, and may extend up to few hectares.
The sun rises early in Arunachal as compared to the rest of the country. And in winter, the sun sets early, by 4.30–5 pm. These squirrels emerge from their roosting sites, usually tree hollows, and self-groom before gliding to the nearest feeding tree. They usually glide short distances of about 10 m. Their moderate distant glides are 20-30 m and long distant glides up to 90-110 m. Though considered folivorous (leaf-eating), I noticed they prefer fruit pulp whenever available. Based on the season, their diet switches between leaves and fruits; they also feed on bark, sap, and flowers.
The unique behaviour of the giant squirrels is their ability to glide. Before they begin a glide, the squirrels climb to the top of a tree or move to have a clear path from where they can glide to the target tree. Before gliding, they analyse wind speed and direction. These lowland tropical forests are extremely windy during certain months, so the squirrels analyse all these factors to gain a soft landing on large broad tree trunks, especially if the distance they are gliding is long. If the wind direction changes in the middle of a glide, they use their tail like a rudder to land safely.
The question that came to mind was, how do they see in such darkness? The answer is that 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 at the back of the eye which reflects light that has passed through the retina. It is like having 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. This is the reason why the eyes of nocturnal mammals appear to “glow” at night.
Red gliding squirrels usually mate once or twice in a year and produce a litter of one or two babies called kittens. They nest in natural tree hollows. Fortunately, I was able to locate few active nests in Namdapha where the young ones kept peeping out of the nest at night. The juvenile did not move much except to step in and out of the hollow briefly. They are secondary cavity nesters that depend on natural tree hollows or holes made by birds like woodpeckers. However, they sometimes make leaf nests. Studying their nesting ecology is extremely difficult in the dense forest.
The squirrel’s call is like a monotonous repeated wail. It is loud and can be heard up to several hundred meters away depending on the wind.
Though this species is widely distributed, it faces enormous threats in its range. Deforestation for agriculture is a key threat. This species is arboreal in nature and the canopy is their highway, if there are large gaps and forests are fragmented, they cannot reach the other end of the forest. Linear infrastructure development is another threat, and individuals get killed by speeding vehicles and high-tension wires. Additionally, these squirrels are killed for bushmeat. A lot remains to be studied and understood about these amazing species and their role in the ecosystem.