17 January,2021 07:15 AM IST | Mumbai | Prutha Bhosle
Pic/Swati Udayaraj
The Travancore flying squirrel, also known as the small flying squirrel, is found in Southern India. It's less sighted due to its crepuscular and cryptic habits. The Indian palm squirrel, on the other hand, adapts easily near human populations in urban areas, plantations and open rural areas. It is also known to be easily tamed by humans. This difference nudged biologist Nandini Rajamani to launch a social media campaign in 2020 that involved public participation. "Indian palm squirrels are commonly seen, and fed and touched by humans. But we don't know what exactly they eat, why they thrive around us unlike the Travancore flying squirrel, and what their life span is," she says, explaining the reason behind using social media and Citizen Science (scientific research conducted by amateur scientists).
Within a few months, Tirupati-based Rajamani and her team hit gold. "We got amazing responses on Instagram and Facebook from a large number of people sharing their observations with us. This was possible because the Indian palm squirrel is found in our backyards. An unknown author sent us a video that shows a female Indian giant squirrel leaping from a tree and across a highway to rescue a baby squirrel. This and many other instances proved that parental care is a vital characteristic of this mammal group," she adds.
Nandini Rajamani, biologist
During the lockdown, Rajamani launched the Instagram page, Squirrels of India. Here, followers can know all about the rodent; its behaviour, the many species that continue to thrive in India, and some rare others that are threatened by human settlements. Rajamani, who is an assistant professor at the department of biology, Indian Institute of Science Education and Research (IISER) Tirupati, explains, "These mammals are an important component of our biodiversity, as they form the prey base for many carnivores and raptors. They affect the plant kingdom, and so, are key to the functioning of the ecosystem. It's unfortunate that very little research has been done on them."
Rajamani and her team work out of the Sciurid Lab in Tirupati. Launched in 2016, the lab studies the behavioural ecology and evolutionary biology of animal populations, often within the context of environmental and habitat change. They work across multiple landscapes in India, including the Trans-Himalayas, Western Ghats and Eastern Ghats. "There are about 40 species of squirrels in India, and about 280 species in the world. Squirrels evolved in Southeast Asia, and then occupied many parts of the world, including India. All of this happened millions of years ago, and we don't know the exact timelines for when squirrels came to India," she says.
However, what is clear is that there is a high diversity of squirrels in India, including in the Northeast, but no real data available on exactly how many species. What makes it more challenging is that it's an animal that's cryptic and difficult to observe. What we do know is that every species has different requirements and that with deforestation and climate change, they are decreasing in number. Rajamani says, "It is crucial that we protect them. But before we get to that, we need to understand them."
In India, Himalayan marmots are found mainly in the UT of Ladakh with their range extending into other Indian Himalayan states as well as countries like Nepal, Bhutan, and China (around the Tibetan Plateau). Long-tailed marmots are found in Jammu and Kashmir and their range extends into Pakistan, Afghanistan, Tajikistan, Kyrgyzstan, Uzbekistan, and western China. Marmots are social squirrels that live in colonies. "They are cold-adapted species that live in high-altitude grasslands and dig burrows underground. In order to deal with adverse winter conditions, they hibernate anywhere between six to eight months. Soon after they emerge from hibernation in the summer, they mate and give birth to offspring underground. Marmots are mostly seen foraging in the day. They emit a sharp whistle-like call on sighting a threat," says Senan D'Souza, project fellow at IISER.
A detailed report on the status and distribution of the Travancore squirrels in the Western Ghats, submitted in 2015 by Rajamani, noted that its choice of habitat might be influenced by larger trees, which are conducive to larger trunk cavities and allow squirrels to glide more efficiently. "In the Western Ghats of Tamil Nadu and Kerala, the research was conducted for a period of four months from February 2000 to May 2000. The Travancore squirrels were encountered only in evergreen and moist deciduous forests. However, the encounter rate was significantly lower. This is because it's a shy and mysterious species. They are an evolutionary oddity. Very few mammals are like this. They don't have a loud call," says Rajamani. A few years ago, she was assigned to radio collar them in the forests. "It is interesting how once they were radio collared, they were never seen again. So even if the signal was strong and we knew they were somewhere close to us, we never saw them again. They are exceedingly shy."
Pic/Ramki Sreenivasan
For flying squirrels in general, females are larger in size than males, making the phenomena unusual for the mammal world. Rajamani says, "We know that from primates, lions and dogs that the norm is males are larger. In terms of flying squirrel, our theory has got a lot to do with aerodynamics of movement. The female has to carry a lot of excess load when she is pregnant. To compensate for this weight gain and not lose efficiency of locomotion, she has a bigger frame. The other explanation is dominance, so that females can protect the young better when they are larger than males." Another theory is that males are smaller because they display talent to mate. "When they do acrobatics display, it helps to be small and agile; the best get selected." The Indian giant flying squirrel, in particular, is a nocturnal arboreal mammal whose population in some sites across the Western Ghats seem to increase with disturbance. Their first instinct is usually to leave the hollow and glide off the tree rather than run up it, and in the process, some animals might fall or get injured. Small cats, leopards and large raptors, including the crested serpent and hawk eagles are all known predators of giant flying squirrels.
Pic/Harsha Kumar
The Indian palm squirrel - the one with three white stripes on its back - is generally seen around trees in south India and Sri Lanka, and eats tree fruit, seeds, and insects. In north India, the five-striped palm squirrel is commonly sighted. Rajamani says, "The five-striped squirrel has a brownish-grey dorsal surface with five pale longitudinal stripes set against a dark brown saddle patch. The three middle stripes are longer than the two lateral ones, and the mid-dorsal or central stripe extends to the tail." But it is the three-striped one that is most commonly known in India, courtesy Hindu mythology. According to the legend, Lord Rama stroked a squirrel's back. Three stripes, marks of his fingers, appeared on it. These live very close to human settlements and are seen nibbling on food, grooming their tails and scurrying up branches with agility. The three-striped palm squirrel is relatively active in the morning. "It actively forages during this time. Its activity is low during peak noon and resumes sometime in the afternoon till late evening. They are very vocal and make a loud chip-chip sound when they see a potential threat. Their lifespan in the wild is not well documented; however, captive individuals have lived for almost 5.5 years," adds Swati Udayraj, a PhD student at IISER.
