Maansi Rawat*

I vividly remember that during the COVID lockdown, I used to go to our terrace just to catch a glimpse of the big and mysterious creatures flying in the sky at dusk. As the sun continued to set and the clouds turned shades of twilight, the sky became their playground. These creatures were bats, the only mammals to have evolved the mechanism of true flight because of their modified forelimbs (see Image 1). It was only during my Master’s internship that I learned they were fruit bats named Pteropus medius (formally known as Pteropus giganteus). I had the opportunity to further investigate these creatures against the backdrop of the urban ecosystem. This blog, inspired by my internship experience, explores the diurnal roosts (the sites used for sleeping and protection during the daytime) of Pteropus medius, present within the dynamics of the urban. This exploration highlights the importance of understanding and appreciating the intricacies of wildlife survival in our changing cities.

Fruit bats, as the name suggests, forage on fruits and flowers. Pteropus medius, commonly known as the Indian Flying Fox, is the biggest and most conspicuous fruit bat found in the Indian mainland (Menon, 2014). Its head is chestnut-brown with pointed black ears, and its body is tan or orange-coloured, resembling fruits and dried leaves (Kunz, 2011). The wings are notably black, with a wingspan of more than a metre. It is further characterised by a lengthy and hairy snout, giving it the appearance of a fox, hence the name Flying Fox (Blanford, 1898; Menon, 2014). Indian Flying Foxes are unable to echolocate, and therefore have well-developed sight and olfaction to locate ripe fruits and flowers (Menon, 2014). Their diet mainly consists of mangoes, bananas, guavas, figs and other available fruits (Senthilkumar & Marimuthu, 2012 ; Dey et al., 2013; Kumar & Kanaujia, 2015). They are responsible for seed dispersal and pollination of many flowering tree species like Kigelia africana (Sausage tree), Haplophragma adenophyllum, Oroxylum indicum (Indian trumpet flower) and Crescentia cujete (Mishra et al., 2020) . Despite performing these ecosystem services, fruit bats are often persecuted due to their utilization for bushmeat and medicinal purposes (Singaravelan et al., 2009). Not too long ago, fruit bats were declassified as vermin following the amendment of Indian Wildlife (Protection) Act in the year 2022.

My friend Anjali and I, as part of our internship, were assigned the task of studying fruit bats in the bustling metropolis of Delhi. Our search for fruit bats around the city took us to old monuments, baolis and buildings. But they turned out to be dead ends because the bats we encountered were insectivorous, whereas we were specifically looking for fruit bats. It was then that a friend mentioned the sighting of fruit bats in Hauz Khas Park. We decided to investigate whether that location could serve as our potential study area. As we neared the Hauz Khas Lake, we observed hundreds of Indian Flying Foxes hanging from the trees (see Image 2) and decided to conduct our internship study at this very site.

The roosts, also known as ptero camps, were observed using binoculars and a camera during the month of July. Direct visual count was employed using the double observer method to estimate the bat population (Thomas, 1989; Mishra et al., 2020). This method involves having two independent observers simultaneously count the same group of animals to reduce potential bias and enhance accuracy. For a significantly large roost, specific branches of the trees that were both visible and easily countable were selected. After completing the counts on these selected branches, the observed numbers were extrapolated, by assuming that the chosen branches provide an accurate representation of the total population present in the roost. This method, known as branch estimation method, is often used to estimate the population of roosting animals.

At Hauz Khas, amidst heritage buildings, reservoirs and sprawling urban culture, we observed thousands of bats. Living in large aggregations, the roosts of Indian Flying Foxes are said to be gregarious, a phenomenon also observed in our study (Dey et al., 2013). Our study roost was also very noisy due to the constant screeching sounds made by the bats (Kunz, 2011; Senthilkumar & Marimuthu, 2012). They were observed to be engaged in various activities, including sleeping, foraging on the fruits, flapping their wings, fighting, copulating, and even rearing their young ones. Further, the Indian Flying Foxes exhibit distinctive preferences for roosting locations. They were often observed roosting on the branches of old, tall and well-canopied trees in proximity to human settlements and water bodies (Senthilkumar & Marimuthu, 2012; Mishra et al., 2020). They were roosting in multiple tree species, suggesting a scattered roost, meaning various trees are used for roosting by individuals. In our study, bats were roosting in 25 trees of 6 different species. The trees were Azadirachta indica (Neem), Syzygium cumini (Jamun), Ficus religiosa (Peepal), Ficus virens (Pilkhan), Bombax ceiba (Semal), Morus alba (Toot), and Acacia nilotica (Babool) (see Image 3). Neem stood out as the preferred choice for roosting, hosting a maximum of 12 roosts (see Image 4). Additionally, as Indian flying foxes have external roosts because of which they tend to lose a lot of water via evaporation (Kunz,2011), roosting near water bodies is vital for their survival. In our study site, we observed roosts near lakes, which served as their drinking source and helped in coping with the ambient temperature (Mishra et al., 2020). Bats used to consume water before leaving their roosts at dusk for foraging. They glided above the lake, dipping their heads and bodies into the water before taking off for their foraging quests (Kumar & Kanaujia, 2015).

Witnessing a mega roost of flying foxes in an urban park piqued our curiosity, leaving us wondering about the factors that make cities suitable habitats for these creatures. Fruit bats are known for their high adaptability and opportunism in selecting roosting locations. Kunz (2013) aptly describes bats as synanthropes, emphasizing their remarkable ability to coexist closely with humans and derive advantages from human environments and activities. As we delve further into the literature, we come across discussions about how urban environments provide advantageous conditions for fruit bats to thrive. These conditions include a warmer climate attributed to the urban heat island effect, ease of navigation facilitated by distinctive landmarks, the presence of fruit-bearing trees throughout the year (Egert-Berg et al., 2021), and a denser distribution of tree species in urban environments compared to rural or natural settings, owing to habitat heterogeneity (Kowarik, 2011).

Fruit bats have become dynamic participants in urban ecosystems, no longer confined solely to natural habitats. Their coexistence with humans reflects a fascinating interplay between wildlife and urbanization, defying traditional notions of nature devoid of humans. Through their ability to adapt and be resourceful in an urban environment, bats and other wildlife not only survive but often thrive in the midst of human activities, contributing to the biodiversity of cityscapes in unexpected and intriguing ways.

References

• Blanford, W. T. (Ed.). (1898). The Fauna of British India: Including Ceylon and Burma. (Vol. 4). Taylor & Francis.
• Egert-Berg, K., Handel, M., Goldshtein, A., Eitan, O., Borissov, I., & Yovel, Y. (2021). Fruit bats adjust their foraging strategies to urban environments to diversify their diet. BMC Biology, 19(1), 123. https://doi.org/10.1186/s12915-021-01060-x
• Kowarik, I. (2011). Novel urban ecosystems, biodiversity, and conservation. Environmental Pollution, 159(8–9), 1974–1983. https://doi.org/10.1016/j.envpol.2011.02.022
• Kumar, J., Kanaujia, A., & Verma, R. (2021). Various threats to survival of bats in district Lakhimpur-Kheri, Uttar Pradesh, India. Asian Journal of Conservation Biology, 10(2), 337-342.
• Kunz, T. H. (Ed.). (2013). Ecology of bats. Springer Science & Business Media.
• Menon, V. (2014). Indian mammals: A field guide. Hachette India.
• Mishra, R., Dookia, S., & Bhattacharya, P. (2020). Avenue Plantations as Biodiversity Havens: A Case Study of Population Status of the Indian Flying Fox, Pteropus giganteus Brunnich, 1782 and Implications for Its Conservation in the Urban Megacity, Delhi, India. Proceedings of the Zoological Society, 73(2), 127–136. https://doi.org/10.1007/s12595-019-00308-3
• Rawat, M. (2022). Day Roost Characterization and Species Interaction of Indian Flying Fox (Pteropus giganteus) at Hauz Khas District Park. Dr. B.R. Ambedkar University, Delhi.
• Senthilkumar, K., & Marimuthu, G. (2012). Tree roosting fruit bats (Chiroptera: Pteropodidae) in Southern Tamil Nadu. International Journal of Applied Bioresearch, 14, 4-10.
• Singaravelan, N., Marimuthu, G., & Racey, P. A. (2009). Do fruit bats deserve to be listed as vermin in the Indian Wildlife (Protection) & Amended Acts? A critical review. Oryx, 43(04), 608. https://doi.org/10.1017/S0030605309990391
• Dey, S., Roy, U., & Chattopadhyay, S. (2013). Distribution and abundance of three populations of Indian flying fox (Pteropus giganteus) from Purulia district of West Bengal, India. Taprobanica: The Journal of Asian Biodiversity, 5(1).
• Thomas, D. W., & West, S.D. (1989). Sampling methods for bats. U.S Department of Agriculture.

Featured Image Credit: Maansi Rawat and Anjali Lomas