The Supreme Court ordered the Union Environment Ministry to conduct a fresh survey of India’s elephant corridors and report the reasons for obstructions within them by October 14. The Court made its order on August 17 while hearing a petition against the practice of using fireballs and other harmful methods to deter elephants from entering human dominated landscapes.

The Court observed that though guidelines existed to ensure the smooth passage of elephants, “owing to certain local factors, the elephant corridors have been impeded/blocked/obstructed.” Elephant corridors are strips of land that facilitate the movement of elephants between two or more viable habitat patches.

In his oral remarks, Chief Justice Surya Kant reportedly said that no state could obstruct such corridors. “Construction of any kind of obstacle or creating blockades in elephant corridors is not acceptable. We are very clear that there cannot be obstacles in the way of wildlife,” the three-judge Bench stated, as per media reports.

The Wildlife Institute of India identified 150 elephant corridors in the country in 2023. Most of these corridors fall outside protected areas and national parks, and are encroached by settlements, agriculture, fences, and other infrastructure projects. Out of the 150 corridors identified, 15 were found to be impaired, 29 were found to be used in decreasing frequency, and no information was available for another 18.

The Supreme Court instructed the Ministry to conduct a fresh survey and submit a comprehensive report “including the necessary steps taken by them to prevent such obstruction.” It also said the status report should include the progress on steps taken to prohibit the use of fireballs, mashaals (fire torches), or any other coercive measure to divert the natural movement of the elephants.

“A specific ban on ‘Hulla Parties’, etc. would also be required in this regard, and this Court shall be apprised about the action taken on the same through the aforesaid status report,” says the order. Hulla parties are groups of people who are tasked with scaring elephants away, often using spiked rods and fireballs. In West Bengal, these groups are recruited by the state government.

Elephants are a Schedule 1 species under the Wildlife (Protection) Act, afforded the highest protections under the law. A contempt plea was filed against the West Bengal government in 2024, after a pregnant female elephant was attacked by a hulla party. The elephant died after a fire-spiked rod pierced her back.

Banner image: A group of elephants crossing the Nepal-India border. Image by Nissan Sharma via Wikimedia Commons [CC BY-SA 4.0].

A new study finds that closely-related Western Ghats frogs living together tend to differ in body size, suggesting that competition and species sorting help determine which species can coexist.

Scientists at the Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, examined body-size differences among species belonging to three frog genera in the Western Ghats: Nyctibatrachus and Micrixalus, which are endemic to the region, and Hylarana, which is more widely distributed. They also examined the frogs’ phylogenetic relationships, distribution and microhabitat use.

The scientists found that stream-dwelling frogs showed patterns of body-size assortment. This was especially evident in the endemic Nyctibatrachus and Micrixalus, where species occurring together were significantly more different in body size than would be expected by chance.

For example, among 27 three-species Nyctibatrachus assemblages, 23 contained species belonging to different body-size classes. Among the 19 two-species Micrixalus assemblages, every pair belonged to different size classes.

The paper’s first author, Kartik Shanker, says the pattern appears to have resulted from competition and “species sorting”, an ecological process in which competition can exclude species with similar traits from local communities while allowing more dissimilar species to coexist.

This pattern, however, was missing in Hylarana. “The two clades (Nyctibatrachus and Micrixalus) appear to have adapted early on in their evolution to streams and ponds, creating a separation,” Shanker says.

The size differences were particularly pronounced among species living in the same habitat. The study found that body-size differences between sympatric Nyctibatrachus species were greater than between species occurring in adjacent but separate areas.

The study also found an association between body size and microhabitat in Nyctibatrachus. Larger frogs tended to occupy faster-flowing sections of streams, while smaller species were more often found along stream edges, away from the strongest flow. Such differences could allow species to use different parts of the same stream and reduce competition.

“Larger bodies allow them to hold on to the rocks in the faster-flowing parts of the streams, smaller bodies allow them to hide in the leaf litter,” Shanker points out as an example of an ecological advantage of this pattern.

However, this relationship was not significant in Micrixalus or Hylarana, suggesting that other forms of ecological niche partitioning may be operating in those groups.

Importantly, the researchers did not find strong evidence that competition directly drove the evolution of body size. Shanker says: “We find that competition did not lead to evolutionary divergence. Thus, the pattern may have come about by species sorting, that is, after divergence into different species, thus more at an ecological than an evolutionary scale. But the driver is competition.”

The study therefore provides evidence that competition can structure biodiversity without necessarily driving adaptive evolution. A potential conservation implication, Shanker says, is that changes to microhabitats could threaten species even when the broader forest habitat remains the same.

Banner image: The Micrixalus kottigeharensis frog species. Image by Dhritiman Mukherjee.

Species File: Exploring India’s biodiversity, one species at a time.

Every winter, hundreds of colossal, leathery-shelled reptiles arrive at Galathea Bay on Great Nicobar Island. They dig deep trenches, lay their eggs, and cover them with sand before heading back into the waters. In around two months, the eggs begin to hatch, and baby turtles take their first steps and head into the ocean, as their ancestors have for millions of years. But now, a large trans-shipment port, planned as part of the Great Nicobar Island project, could threaten the turtle’s survival on this beach.

The leatherback turtle (Dermochelys coriacea) is the largest of all living sea turtles and is the only one without a hard shell. It instead has a leather-like, flexible carapace that allows it to dive deeper (up to 1,000 metres) than other turtles. Adults can grow nearly two metres long and weigh as much as a compact car (1,000 kilograms). The turtles feeds almost entirely on jellyfish, helping keep their populations in check and maintaining ecosystem balance.

Leatherbacks are found in every ocean except the Arctic and Antarctic and spend most of their lives in open waters. The females of the species migrate thousands of kilometres from foraging grounds to nest on open sandy beaches in tropical and subtropical countries. In India, they nest almost exclusively in the Andaman and Nicobar Islands, with Galathea Bay being the largest nesting ground in the northern Indian Ocean. Other major global nesting spots are located in Gabon, Trinidad and Tobago, Suriname, Costa Rica, Indonesia, Papua New Guinea, and Mexico.

The IUCN lists the leatherback turtle as globally vulnerable due to declining populations. In India, it has the highest legal protection under Schedule I of the Wildlife (Protection) Act, 1972, offering it the highest protection from hunting, poaching and trading.

Loss of nesting sites, due to development activities and beach erosion, is one of the key threats to the turtles’ survival. They also get caught as bycatch in fishing operations, collide with boats and ingest plastic waste. Artificial lighting near nesting beaches also deters adult females from nesting and also disorients the baby turtles. Particularly in Nicobar, the ₹81,000 crore (₹810 billion) trans-shipment project includes building an international container port on the leatherback turtle nesting site, as well as an airport, gas and solar power plant, and township which will lead to the felling of a million trees.

Read more about the leatherback turtle conservation in the Little Andamans, environmental clearances surrounding the Great Nicobar project, and how turtles adapt to climate change.

Banner image: A juvenile leatherback turtle. Image by Ken Clifton via Flickr (CC BY-NC 2.0).

Species File: Exploring India’s biodiversity, one species at a time.

In the forests of northeast India, a series of whoops and hoots rises through the canopy in a melodious crescendo every morning — the unmistakable song of the western hoolock gibbon. Pairs often duet to mark their territory, reinforce pair bonds and communicate with their family members.

The western hoolock gibbon (Hoolock hoolock) is India’s only ape. While adult males have a fully black coat, females are buff to golden-brown. Exclusively arboreal, which means they spend their lives on trees, they use their long arms to swing between branches with ease. They feed primarily on fruits, and occasionally leaves and insects, making them vital for seed dispersal and forest regeneration.

In India, the species is found in the tropical and subtropical forests of the northeast, across Assam, Arunachal Pradesh, Meghalaya, Manipur, Mizoram, Nagaland, and Tripura, with populations extending into Bangladesh, Myanmar, and perhaps southern Tibet. Two other hoolock gibbon species — the eastern hoolock gibbon (Hoolock leuconedys) and the Gaoligong hoolock gibbon (Hoolock tianxing) — are found in Myanmar and China.

An estimated 90% of the global hoolock gibbon population has been lost over the past three decades. Around 3,000 western hoolock gibbons are believed to remain; 2,600 of them in India. According to the IUCN Red List, the western hoolock gibbon is listed as endangered, as is the Gaoligong hoolock gibbon; the eastern hoolock gibbon is listed as vulnerable. The species receives the highest level of legal protection in India, under Schedule I of the Wildlife (Protection) Act, 1972.

Hoolock gibbons require contiguous, closed-canopy forests for survival, and are thus highly vulnerable to habitat loss and fragmentation. The loss of even a single connecting tree can render fragments unreachable. Hunting and the illegal pet trade compound the pressure.

In an earlier story published by Mongabay-India in 2019, primatologist Narayan Sharma, Cotton University, Assam, said: “When a contiguous habitat is reduced to scattered smaller fragments, they become ‘habitat islands’ in an inhospitable sea of degraded habitat. This could result in inbreeding. The resultant offspring are often weak, sometimes sterile or may have little reproductive fitness.”

Read more about the hoolock gibbon in our stories on saving India’s only ape, community conservation efforts, and how tree bridges could help connect fragments.

Banner image: A western hoolock gibbon in Namdapha Tiger Reserve. While adult males have a fully black coat, females are buff to golden-brown. Image by Rohit Naniwadekar via Wikimedia Commons (CC BY-SA 4.0).

Global biodiversity assessments have often suggested that the impacts of invasive alien species are greatest in wealthy countries of the Global North. A new study, however, challenges this notion and establishes that the severity of environmental impacts is generally higher in the Global South and calls out research bias for distorting the global picture.

The study, published recently in Science journal, combines two global datasets: GIDIAS, which contains more than 22,000 documented impacts involving over 3,300 invasive alien species from more than 6,700 scientific and grey-literature sources across 172 countries, and SInAS, which records the distribution of more than 39,700 alien species worldwide.

Considering research effort and the number of reports are much higher in the Global North, simply counting invasive species or documented impacts can make the region appear disproportionately affected. To better understand the impact, researchers, Sven Bacher, Petr Pyšek and Hanno Seebens used the IUCN’s Environmental Impact Classification for Alien Taxa (EICAT) under which an impact is considered severe when an invasive species causes a decline in a native population, local extirpation or global extinction.

Rather than simply counting how many invasive species or impacts have been recorded in a region, the researchers calculated average impact severity: the proportion of documented impacts that are severe. This was intended to reduce the effect of differences in research effort between countries.

The key findings include higher average impact severity in the Global South, the influence of research bias on assessments of invasive species impacts, the particular vulnerability of emerging economies, and the role of governance and management capacity in determining impact severity than large economies in the Global North.

The paper identifies India as one of the large, high-income developing economies where this pattern is visible. India has relatively high absolute numbers of documented impacts, but also a distinctly higher average impact severity than large economies in the Global North.

One of the biggest takeaways from the study is that weak governance and limited management capacity act as major drivers of high impact severity. Failure to recognise the Global South as facing the highest IAS impacts diverts attention away from the most threatened regions.

Previous research has identified emerging economies as countries likely to see the largest increases in alien species numbers in the near future as a result of strong economic development, potentially leading to more impacts, many of them severe. By contrast, wealthy countries of the Global North may have high introduction rates of alien species but also stronger governance and better management capacity as compared with the Global South, allowing them to implement policies and manage invasive species more effectively. The paper shows that good governance and effective management can reduce the impacts of biological invasions across most taxa and ecosystems.

Banner image: Invasive giant African snails spotted in Kerala. Image by Drajay1976 via Wikimedia Commons (CC BY-SA 3.0).

Species File: Exploring India’s biodiversity, one species at a time.

They sleep upside down and hunt for prey in the dark using sound waves — what can’t bats do? The only mammals capable of true flight, bats are remarkably adaptable, found on every continent except Antarctica. They offer critical ecosystem services by preying on insect populations, including agricultural pests and disease-carrying insects. For example, the critically endangered Kolar roundleaf bat (Hipposideros hypophyllus) that survives in a single cave in Karnataka is known to munch on 4,100 species of insects, including mosquitoes that transmit dengue and malaria.

India has roughly 135 species of bats — about 10% of global diversity — of which around 16 are endemic. The Western Ghats alone host at least 63 species, including the rare Wroughton’s free-tailed bat (Otomops wroughtoni). The Western Himalayas are home to 53 species of bats, including the East Asian free-tailed bat (Tadarida insignis), which until recently, was not recorded in India. Bats have also adapted to cities, roosting in old trees, under roofs, temple groves or heritage buildings.

The ecology of bats can vary surprisingly. The Indian flying fox (Pteropus giganteus), India’s largest bat with a wingspan of up to 1.5 metres, forages by sight and smell rather than echolocation. The palm-sized painted bat (Kerivoula picta), with its bright orange fur and black wings is vulnerable to the illegal wildlife trade.

Aside from insectivorous bats that control pests, India also hosts nectar- and fruit-feeding bats that pollinate flowers and disperse seeds, while their guano enriches soil with key nutrients.

Despite the many crucial roles played by them, bats remain among India’s least protected wildlife. Only six of the species found in India carry the highest legal protection under Schedule I of the Wildlife (Protection) Act. According to Bat Conservation International, of the 122 Indian bat species assessed by the IUCN, only 23% have stable populations, while the rest are declining.

Threats include habitat loss from deforestation and agricultural expansion, roost destruction in caves and old buildings, persecution linked to myths and fears of disease, and, increasingly, collisions with wind turbines.

In a story published by Mongabay-India in 2023, agroecologist Iqbal Bhalla, said: “There is no doubt that bats are incredibly important to agricultural landscapes. I hope that in the next few years we can get to a more definite answer as to exactly what their economic value is in Indian agriculture.”

Read more about bats in our stories on Meghalaya’s bat diversity, and Tamil Nadu’s bats being erased by urbanisation.

Banner image: An Indian flying fox perches on a banana tree. Image by Praveen P. via Flickr (CC BY-SA 2.0).