It was a very windy afternoon, the skies were grey, and a storm was imminent. It was summer and unbearably hot, so the strong wind was a welcome relief. I was sitting under a tall Terminalia arjuna (Arjun) tree near a stream, watching a Malabar Giant Squirrel’s nest. Suddenly, the squirrel came out of the nest and started wildly running up and down the tree trunk and leaping from branch to branch. I was flabbergasted, and paused, not knowing what to note down in my datasheet. What was this behaviour? It simply seemed to have no purpose at all. For several minutes, I watched the squirrel rushing about madly, and my bewilderment turned into amusement.
As scientists, we have been taught to observe and interpret animals as doing ‘meaningful’ things related to finding food, finding mates, resting, or avoiding predators. We are also warned against anthropomorphising. But this squirrel was simply running out of some kind of mad joy. After much dithering, I finally put down the behaviour firmly as ‘playing’. While play behaviour has been noted in most mammals, it is usually in a social context where there is some perceived advantage. It was surprising to observe this sort of crazy ‘playing’ before stormy weather, in a solitary individual. I wonder if there really is any adaptive explanation to it.
The Malabar or the Indian Giant Squirrel Ratufa indica is a brightly coloured arboreal squirrel found in the central Indian forests and in the Western Ghats. Amongst squirrels, these are the heaviest in India, and can weigh up to 2 kg. There is much geographical variation in its colour forms, and several races /sub-species are recognized. It is active in the daytime, retiring to its nest at dusk. Squirrel nests – built of twigs and leafy branches – are called dreys. A giant squirrel makes many such nests in its home range, and could have up to 8 or 9 nests simultaneously. These are mainly for sleeping in, and are changed periodically. It’s easy to figure out which nest is active, based on the freshness of the leaves and the tightness of the structure. Old, inactive nests are brown and loosely held together, which may be repaired and re-used. They are careful to source their building material from elsewhere, and would never tear leafy branches from the tree on which they were building the nest. I had once seen the inside of a fallen nest, and it was lined with soft, cottony balls of the Silk Cotton tree. While all squirrels use and build nests to sleep in, giant squirrels also have special ‘nursery’ nests, where the mother gives birth to pups which share the nest with the mother until they become independent.
Giant squirrels are up at the crack of dawn to start foraging within their ranges, which are usually around 1 to 2 hectares. Often, I would start from our camp to begin my observations at 5-6 am, while still dark. And every evening, I would stop my observations after seeing off the focal animal I was following, into its nest. It was important for me to know which nest the squirrel had gone to sleep in, so that the next morning, it would be easy to locate the individual.
I spent 6 months from December to May, studying and understanding giant squirrels’ foraging and range use, related to food availability patterns; therefore, I had to observe individuals. With most wild species, it is impossible to tell individuals apart unless they are marked or tagged. But with giant squirrels, there are ways to identify most individuals, as they often have one ear cut or bent due to territorial fights, or some differences in facial markings, or some quirky colouration / patterns of their long, bushy tails. It was hard at first, and I lost a few animals I thought I could identify. But after a month, I managed to confidently identify five individuals whom I could follow. My work mainly involved keeping a continuous record of behaviours to understand their space-use patterns and time-budgets through the day. It was quite tiring and frustrating on some days when the focal squirrel would decide to make long, sudden foraging movements into new areas away from its core area. But on most days, they remained in the core area.
On some days, I would do other work like laying grids in the areas used by the squirrels I followed. This was done to map all the food trees, nest trees and other trees in their ranges, and to determine their daily and overall ranges. I also tracked the phenology (leaf, flower and fruit) of all the trees in these grids twice a month to understand seasonal food availability patterns for the squirrels. I got used to constantly craning my neck up to look into the canopy, and at times when the squirrel would stay put, it was a relief to lie down and watch them with my binoculars.
It was a period of discovery, learning new things each day just by watching their behaviour. One morning, the squirrel I called ‘Bent Ear’ was foraging on the unripe fruits of Terminalia bellerica (Behera). Then, it moved up the tree to the topmost leaves and started picking up the leaves and licking them. Initially, I could not understand it; suddenly, it dawned on me that it was licking the dew-laden leaves for water. Langurs who shared the squirrels’ habitat also did the same thing. Another time, a squirrel drank water from a tree hollow. I also learnt other random things- that squirrel poop is neat, small cylindrical pellets, and hard with a distinctive smell. I observed scent-marking and vocalizations used to advertise and mark territories. Giant squirrels have very distinctive alarm calls – remarkably loud, machine-gunning staccato calls. Another call I learnt was a lesser-known contact call made while on the move through the canopy; this was a soft clicking call, as if to let all the other tree creatures know it was coming.
Seasonal shifts in food availability meant that each day I discovered different food items that squirrels ate. Over six months, I recorded around 22 species in their diet, with the main food being the seeds of Terminalia arjuna and Terminalia bellerica. They would adopt various acrobatic postures while feeding – a common one is hanging upside down using their tail as an anchor over the branch, while feeding on some fruit or flower with their front paws. It was important to figure out the exact plant part they were feeding on – I sometimes thought I observed them feeding on flowers, but looking closely, I realized they were actually feeding only on the flower peduncles. I also observed squirrels licking termite-infested bark and eating soil on some occasions. Squirrels fed on sprouting and mature leaves, and tree barks too; they would strip off the outer hard covering and eat mainly the softer phloem/pith inside.
As summer approached, there would be a lull in the morning feeding frenzy and the squirrels would take time off to rest by early afternoon. They would sometimes lie spread-eagled on their belly in the shade, on the lower, horizontal broad branches of trees. On one occasion, it was an amusing sight to watch a langur also resting on its belly with its arms and legs dangling down just a few meters from a squirrel.
The giant squirrel is a solitary creature, but has overlapping ranges. There would be different kinds of interactions amongst squirrels, depending on the sex and age/status of the neighboring animals. Many preferred resources were rare, and the spatial and temporal variation in food supply resulted in overlaps between individuals at locally abundant food resources. Since the defense of an exclusive area guaranteed of resources perennially is not possible, encounters were often avoided by spatial time-sharing. When encounters did occur, there would be aggressive territorial chases. But at super-abundant food resources, it was a common sight to see up to four individuals feeding at the same time. I soon realized that they maintained some distance (5-10 m) from each other and foraged in their own space, and only if any individual came close would there be a chase. This tolerance could be also related to some dominance hierarchies that existed; for example, the sub-adult male I followed, showed in several interactions that it was subordinate to the other two adults.
Towards April, when several squirrels had their pups, I watched mothers coaxing and teaching the pups to jump. The mother would jump first and turn around, waiting for the pup to follow. The pup would reach the edge and keep hesitating, and turn back. The mother would jump back, approach her pup, and then again jump across, as if to show the pup how to do it. Finally, after several attempts, the pup would jump. Studies show that pups stay with their mothers for eight months to a year.
Giant squirrels are believed to be completely arboreal and need canopy continuity in their habitats. However, one part of my main study site was in a disturbed area, with several breaks in the canopy, and a major one where a road cut across. On several occasions, I saw giant squirrels coming down to the ground to cross small stretches where they had no choice. Although this is risky for an arboreal animal, it was heartening to see that some individuals in the population had the ability to adapt to a disturbed habitat. Their diet also indicated their adaptability – I was often surprised when my focal animal fed on the flowers of exotic tree species which grew in certain areas.
I recorded some very unusual behaviour during the winter months. There was very little of the squirrels’ preferred food (unripe fruits and seeds), in the undisturbed riparian habitat. Given that, I expected the squirrels to move around a lot more, searching for food in new areas, or, make a dietary switch to eating more leaves and bark. Instead, to my surprise, they spent long hours simply resting and basking in the daytime. Though occasional forays were made to eat, these were of short duration, and no food was located. So, it appeared that in times of food shortage, these squirrels adopted a strategy of conserving energy and minimizing their requirements by resting.
I recorded another undocumented behaviour during April-May, when daytime temperatures were high. The squirrels started spending long hours in the nest in the daytime. The first day this happened, I worried if I had approached too close and disturbed the animals by my presence. However, over the next few days, it happened with all the individuals I was following, and I also noticed the non-focal individuals in the area doing this. They were all going into the nest at 9 or 10 am and coming out only after 3 or 4 pm, to do some quick feeding before dark. It was especially surprising because I spoke to a couple of biologists who had studied giant squirrels, and they had never observed long periods of daytime resting inside the nest. From watching them over days, I hypothesized that it was possibly too hot to spend time foraging, and instead of resting on branches where they may be at risk of predation by raptor species active at mid-day, they chose to go into the safety of their homes.
There was a fair bit of excitement during my study as I observed unsuccessful predation attempts by Crested-hawk Eagles on giant squirrels. One of the attempts occurred while I was observing a squirrel feeding on an Arjun tree. Two other squirrels were feeding on the same tree, while on a nearby Silk Cotton tree were two more individuals. A Crested-hawk Eagle flew in and perched on this tree; it did not seem to be hunting actively. The two squirrels immediately mobbed it and let out loud alarm calls repeatedly. The eagle responded with outstretched wings, but did not attempt to catch them. After a while, as one of the squirrels left the tree, the eagle swooped down to catch it. The squirrel, instead of fleeing, immediately turned around and faced the predator and called. In the meantime, the other squirrel also started mobbing the predator. The squirrels on the nearby tree also started alarm calling. The eagle made another half-hearted attempt at catching, and then flew away. It was surprising to see five different squirrels ganging up on a predator together.
On all occasions of such attacks I had observed, the squirrels responded by ‘mobbing’ the predator. In a behaviour which seemed suicidal, they approached the predator very close and gave repeated alarm calls in full view of the predator; startled by the prey’s response, the predators did not attempt to catch them after the repeated mobbing. But on occasions when raptors flew overhead, squirrels refrained from giving any alarm call and remained quiet by either becoming alert or flattening their body against a branch.
I have fond memories of those days spent watching the giant squirrels – my first foray into real field work and my first field research study. The insight and understanding one can get from following an animal and watching its behaviour over months is impossible to obtain from the mostly indirect methods we use to understand the lives of many species. My only grouse with watching them was the crick in my neck from looking up into the canopy all the time. That training was useful in the later years, as my field-work always involved arboreal creatures, from squirrels and primates to hornbills. So, every opportunity I could, I would try to lie down to watch them. I also got used to involuntarily scanning canopies. I remember Dr. AJT Johnsingh yelling at me while on a drive “Appu, stop looking up at the canopy and concentrate on looking out for terrestrial mammals now!”