Heatwaves are killing India’s fruit bats, crucial to pollination and seed dispersal

Hundreds of Indian flying foxes (Pteropus medius formerly Pteropus giganteus), large fruit-eating bats, dropped dead in droves in the northern states of India due to intense heatwaves. In Rajasthan, where temperatures soared over 45 degrees celsius in May, there were multiple mass deaths, with 400 in one case, and 300 in another.

“They died as all water bodies near their roosts had dried up and they could not drench themselves in water to cool off,” said Dau Lal Bohra, a wildlife researcher and head of the Department of Zoology at Seth Gyaniram Bansidhar Podar College in Rajasthan. Municipal authorities sprinkled water near their roosts to provide some respite but the damage had already been done, Bohra said.

Bat deaths were also reported in Jharkhand, Delhi, Uttar Pradesh and Madhya Pradesh over the last month. While a number of flying foxes had died in the heatwaves last year, their numbers were in the dozens, unlike this year.

This particular bat species is found only in South Asia, and plays a vital ecological role as a pollinator, and the dispersal of seeds. Until recently, though, it has attracted little research interest. It is listed as being of “least concern” in the IUCN Red List, which means that although its population is declining, it is still plentiful in the wild.

There are no exact numbers available, but conflicts with fruit growers led to a culling of the flying fox in the Maldives, leading to 80% of the population being wiped out. More worryingly, heatwaves seem to be connected to the local extinction of the species in southern Pakistan, which borders northern India.

Vulnerable to heat

C Srinivasulu, professor of zoology and director at the Centre for Biodiversity and Conservation Studies at Osmania University in Hyderabad, said that extreme weather fluctuations have also led to mass bat deaths in Australia. In 2014, as Australia experienced one of its hottest summers, about 23,000 spectacled flying foxes – a related species – dropped dead.

Baheerathan Murugavel, research associate at the Indian Institute of Science Education and Research Mohali, said that Indian flying foxes spend the day hanging in open tree branches, thus exposed to bright sunlight, making them vulnerable to high temperatures.

But in India, there are few studies to estimate the impact of heat waves on bat populations. One such study reporting mass mortality due to a heatwave in West Bengal was done in 2010.

Sumit Dookia, assistant professor at the University School of Environmental Science, GGS Indraprastha University in New Delhi said that summer months are the calving season for these bats, which adds to the problem.

“These bats only have one pup a year, meaning that if these babies die due to heat with the mothers, the survival of the population will be at stake if no efforts are made to protect them,” he said

Ecological losses, zoonotic diseases

Indian flying foxes play an important part in seed dispersal, providing a key ecosystem service. When seeds pass through the guts of these mammals, the acid in the gut dissolves the outer layer of the seeds, increasing their chances of germination.

A report on sustainable management of forests through ecosystem services of bats states that bat-dispersed seeds affect the natural re-colonisation of the lost population of plant species as well as the propagation of many endemic trees that sustain other endangered fauna.

Srinivasulu told Dialogue Earth, “Though there are no scientific studies on this in India, [but our observations] have shown that in the places where fruit bat colonies have disappeared, regeneration of trees has gone down. We have around 200 species of trees in India that are dependent on bats for pollination,” he said.

“In a local ecosystem around 18 to 20% of plant species are night-blooming, and of these around 50% are dependent on bats for pollination. This means that if fruit bats disappear, the ecological losses will be huge.”

He added that fruit bats and plants dependent on them for pollination evolved together. The plants have wider funnels for the bats to drink nectar. As the bats drink, pollen from the plants gets stuck to their wide wings, and is then dispersed when the bats fly off, pollinating the area. If bats are lost, many of these plant species will be lost too.

Plants used in textiles, foods and medicine, like silk cotton tree (semal), bitter bean, cashew nut, and mahua are examples of a few bat-pollinated plant species in India. The economic benefits drawn from these plants are huge and spread across several sectors.

“Indian flying foxes can carry seeds to more than 100 kilometres… and the decline in these bat numbers will directly affect the ecosystem services we get from them. But unfortunately, we do not have much research in India to quantify the losses,” Murugavel explains.

Another concern is that, if the bat population falls steeply, there could be a spillover of diseases from them to humans. The Covid-19 pandemic was, according to some sources, linked to a virus found in bats.

Srinivasulu said, “When we disrupt bats’ habitats their stress mounts, rendering viruses more virulent. This stress-induced virulence can lead to the proliferation of viruses from one host to another, underscoring bats’ potential to disseminate zoonotic diseases.”

He added, “Every living organism, including humans, is a potential zoonotic vector. Some organisms harbour higher viral loads than others, while some, like bats, possess such robust immunity that pathogens have minimal impact on them.”

Nonetheless, he suggested that emphasising the risk of zoonotic diseases may be counterproductive, as misinformation about the large bats has already sparked unnecessary fears, leading to indiscriminate bat killings.

Stigma hinders conservation

Up until the latest amendment of the Wildlife Protection Act, 1972, the Indian flying foxes were listed under Schedule V of the Act, as vermin – making their killing acceptable – because they feed on fruit-bearing trees.

The caretakers and owners of such orchards considered such feeding as damage to their crops. Indian flying foxes, though, were moved to Schedule II, which has severe penalties for killing animals in its list, from Schedule V, after the latest amendment of the Act in 2022.

But the bats are suffering also as part of the overall degradation of ecosystems. A study from Haryana shows that these bats prefer tall trees with broad canopies, but such tree cover is becoming harder to find. According to Global Forest Watch lost 2.33 million hectares of tree cover from 2001 to 2023.

“Linear infrastructure development impacts these bat colonies as they roost for 50 to 60 years on the same trees. As urban areas expand laterally these bats will lose their suitable habitats. As per our estimates, around 80% of the Indian flying fox colonies currently known to us in India will be lost in the next 30 years,” added Srinivasulu.

Shuchita Jha is a freelance environment journalist based in India. Her work focuses on the interconnectedness of the environment, climate change, just transition, and human rights. Her handle on X is @Shu_cheetah and Instagram is @shuchitajha

This article was originally published on Dialogue Earth under the Creative Commons BY NC ND licence.