All about flying squirrels
The 21st of January each year is observed worldwide as Squirrel Appreciation Day. On this occasion, Sumashini P. S., a research fellow with Ashoka Trust for Research in Ecology and Environment (ATREE), Bengaluru, pens down some of her memorable encounters with flying squirrels in various parts of India. Read her blog to know more about the superheroes of the squirrel world.
It was sometime in late January 2018. We seized a weekend to make a quick visit to Chakrata, from Dehradun, to catch a glimpse of the Himalayas in winter. Clothed in several layers, we decided to go for a night stroll. There was nobody else save the deodar trees, the fallen snow, the comforting cold, the silence and the clear night sky full of stars. We were alert, hoping to see some owls, the enigmatic birds of the night. Suddenly, a sensation of something gliding above our heads caught our attention and created excitement. We managed to get only a glimpse of it, but we knew what it was – a flying squirrel. We ran in the direction it glided in and located it again. There it was, the red giant flying squirrel (Petaurista petaurista), sitting cosily on a branch and actively scrounging for some fine pine cones. Its day had just begun when most others were fast asleep.
South Asia is known for its high diversity of flying squirrels. There are about 17 species belonging to 7 genera (Datta & Nandini, 2005). In India, most of these species are found in the eastern Himalayas and the north-east, at the confluence of two biogeographically significant regions, the Himalayan and the Indo-Malayan regions. A study that was conducted in Arunachal Pradesh reported occurrences of a whopping number, 14 species of flying squirrels from the state, with the red giant flying squirrel being the most common one, followed by the parti-coloured flying squirrel (Hylopetes alboniger) (Krishna et al., 2016). In the western ghats, two species, the Indian giant flying squirrel (Petaurista philippensis) and the Travancore flying squirrel (Petinomys fuscocapillus), are reported to occur.
Flying squirrels, not quite concurring with their etymology, do not fly but are known for their unique ability to glide. This is made possible by the patagium, the skin membrane between the hind limbs and forelimbs. When the squirrels flatten their bodies and spread their limbs, the membrane expands, allowing them to glide. Otherwise, it is folded in. It’s simply enthralling to watch them glide! They look like a flat parachute with a tail, as though a creature from the realms of fantasy, gliding away with great speed, evoking awe and excitement every time one sees them do it. They do manage to change direction while gliding, which is probably made possible by the deft use of the tail.
The high diversity of gliding squirrels in the tropics of Asia has been attributed to the forest structure. These forests are dominated by dipterocarp trees that emerge above the canopy with no lower branches. Since gliding can make these animals vulnerable to predation, it is hypothesised that they have evolved to be nocturnal. This provides an additional benefit of segregating themselves from other species that use similar resources during the day, be it other tree squirrels and primates. Though flying squirrels are known to be predominantly leaf-eating animals, fruits, flowers and seeds also constitute a good portion of their diet. In one such instance, we were lucky to witness the red giant flying squirrel feasting on Bombax ceiba fruits during the night, having the tree all to itself. This was in Kakojan RF, a remnant lowland wet evergreen forest fragment in eastern Assam. In a larger patch of forest around the same area, in Dehing Patkai Wildlife Sanctuary, we witnessed this species feeding on the leaves of Kadam (Neolamarckia cadamba) tree. We also regularly saw three individuals of parti-coloured flying squirrel, which had made a mango tree near the ranger’s office their haunt. We found them feeding on mango flowers.
Another memorable encounter with a flying squirrel was around the Chinnar Wildlife Sanctuary in Kerala. This time, it was the Indian giant flying squirrel, in the most unlikeliest of circumstances – while waiting for a flat tyre to be fixed! In what seemed like a human-dominated area, but with home gardens and few patches of trees here and there, we saw the species glide close to 25 m or so at the onset of dusk. We also encountered this species in the forest fragments around Valparai.
More About Flying Squirrel
- They are known to nest in tree cavities
- Very less is known about these species – more studies on ecology, populations of flying squirrels required
- Habitat degradation forms major threat, although hunting pressure is less owing to nocturnal behaviour. Flying squirrels do seem to be tolerant from our encounters in forest fragments and degraded habitats as recognised by other studies in the fragments of western ghats (Nandini 2008).
- Most squirrels have bushy tails, large eyes and occur in three body forms—tree, ground and flying. Taxonomically, they are separated into five subfamilies: Ratufinae, Callosciurinae, Xerinae, Sciurinae and Sciurillinae.
- Ground and tree squirrels are diurnal while flying squirrels are nocturnal. Diurnal, arboreal sciurids have the largest brain size of any rodent when brain weights are regressed against mean body weight reach 2.5 kg.
- While the ground squirrels are largely grazers, many of the diurnal arboreal squirrels are seed predators, also consuming shoots, bark and leaves, and some are more insectivorous. Most of the nocturnal flying squirrels are believed to be more folivorous than diurnal arboreal squirrels, though the degree of folivory varies.
- Flying squirrels are represented by 17 species in 7 genera in South Asia; nine species of large flying squirrels and eight species of small flying squirrels.
Krishna, M. C., Kumar, A., Tripathi, O. P., & Koprowski, J. L. (2016). Diversity, distribution and status of gliding squirrels in protected and non-protected areas of the Eastern Himalayas in India.
R. Nandini, N. Parthasarathy, Food Habits of the Indian Giant Flying Squirrel (Petaurista philippensis) in a Rain Forest Fragment, Western Ghats, Journal of Mammalogy, Volume 89, Issue 6, 16 December 2008, Pages 1550–1556, https://doi.org/10.
Sciurids, Datta, A and R, Nandini, Mammals of South Asia.
Written by PS Sumashini
PS Sumashini is a research fellow with ATREE and is an alumnus of the Wildlife Institute of India, Dehradun. Though her interests are constantly evolving, behavioural ecology is closest to her heart. She is also interested in tropical forest ecology and reconciliation of biodiversity conservation and agriculture.