- Tigers in Nepal are increasingly isolated in protected areas and facing difficulties moving within the country due to human activities and habitat fragmentation.
- Domestic corridors in the Siwalik hills could connect the tiger populations and increase their genetic diversity and viability.
- Conservationists recommend involving community forest user groups and implementing wildlife-friendly infrastructure guidelines to manage and protect the domestic corridors.
KATHMANDU — When India announced the results of its national tiger census in April this year, it added a new habitat for the big cats: the Suhelwa Wildlife Sanctuary in Uttar Pradesh, which borders Nepal.
Researchers had captured images of two tigers in the sanctuary, one of which had the same stripes as a tiger photographed in Nepal’s Banke National Park, suggesting that it had crossed the border.
“This was a sign that the transboundary corridors connecting tiger populations in India and Nepal were functional and that tigers could move from one protected area to another,” said conservationist Hem Sagar Baral, co-author of a recent modelling study to identify and assess both domestic and transboundary potential tiger corridors.
It also highlights the landscape-based approach that the two countries adopted in the early 2000s to save the tigers in the Terai Arc Landscape (TAL), a flatland region along the Ganges and its tributaries, said Tek Raj Bhatt, lead author of the study.
But while tigers can cross borders, they face more challenges moving within Nepal, conservationists say. “We have invested so much in transboundary corridors, protected areas and buffer zones, but not adequate attention has been paid to domestic corridors,” Bhatt told Mongabay.
The TAL in Nepal used to be a continuous forest where tigers roamed freely until the 1960s, when an east-west highway was built across it. The forests were cleared for the highway, which brought migration and made human travel easy but blocked the tigers’ movement.
In recent times, human activities such as development of new settlements and roads and mining have further fragmented the tiger habitat, confining them to protected areas in Chitwan and Parsa in the east and Banke-Bardiya and Shuklaphanta in the west. All this is believed to have reduced their genetic diversity and made them vulnerable to inbreeding and diseases.
Official data show that Nepal is now home to 355 wild tigers, nearly triple the figure of 121 from 2010.
A study in 2017 identified three distinct subpopulations of tigers in Nepal’s TAL and found that only a few tigers had migrated between them.
Another camera trap survey by the semi-governmental body National Trust for Nature Conservation in the Siwalik (Chure) hills, the outer Himalayan hills on the edge of the TAL, corroborated this as tigers were spotted outside the protected areas, indicating that they were trying to disperse.
Bhatt and his team wanted to find out where tigers could potentially move around between different areas easily and where they faced difficulties. They mapped the tigers’ energy costs of traveling based on factors such as terrain, vegetation and human density. They also consulted experts who had studied tiger movement and used a method called circuit theory to chart the best routes for connecting tiger habitats.
They found nine potential tiger corridors within Nepal and adjacent areas in India—some new, some previously identified—that could facilitate tiger movement. Most of them were located in the Siwalik hills.
But these hills are also where human activities have increased rapidly in recent years, threatening the corridors. Baral said that although the forest cover was intact, it was getting difficult for tigers to use them. “We also need to look at the prey densities. Tigers can’t move around without eating for long periods of time,” he added.
The study suggested that tigers moving between the Chitwan-Parsa-Valmiki complex and Banke-Bardiya complex could use protected areas south of the border such as Suhelwa Wildlife Sanctuary as stepping stones. Similarly, Katarniaghat Wildlife Sanctuary and Dudhwa National Park could help tigers move from the Banke-Bardiya complex to Shuklaphanta.
“If we could facilitate the movement of tigers through the Siwalik range, there’s potential to increase the population in habitats such as Shuklaphanta,” Bhatt said. “In addition to this, if the tigers can move freely, we may have fewer incidents of negative interactions.”
The study’s co-author, Ali Chauvenet, senior lecturer at Griffith University in Australia and biodiversity theme leader at Center for Planetary Health and Food Security, said the study presented not just issues related to connectivity among isolated subpopulations of tigers in the Terai Arc Landscape in Nepal and India, but also a promising solution to improve.
Bhatt, the lead author, said that Nepal’s community forest program, hailed globally as a successful initiative, could be roped in to help manage corridors in the Siwalik region. “If the community is involved, it could be more sustainable,” he added.
Similarly, the recent wildlife-friendly infrastructure guidelines need to be implemented strictly so that roads that cross tiger habitats don’t impede their movement, he added.
Conservationist Babu Ram Lamichhane, who wasn’t involved in the study, said the main takeaway from the study is that the Siwalik hills (Chure) are important not just for hydrogeological reasons, but also for tigers and biodiversity. He said this should be one more reason to save the hills.
Banner Image: Tigers photographed by a camera trap in Nepal. Photo credit: DNPWC/NTNC/Panthera/WWF/ZSL
Bhatt, T., Baral, H. S., Thapa, K., & Thapa, G. J. (2021). Identifying potential corridors for tiger movement in Nepal’s Terai Arc Landscape. Ecology and Evolution, 11(2), 1014–1027. https://doi.org/10.1002/ece3.10140
Sadhu, A., Patra, M. K., Bhattacharya, Y., Ojha, P., Jain, D., Thakar, R., … V. Jhala, Y. (2022). Recolonisation of tigers recorded from camera trap survey in Suhelwa WLS in India. CATnews. Retrieved from https://www.researchgate.net/profile/Ayan-Sadhu-2/publication/362850461_Recolonisation_of_tigers_recorded_from_camera_trap_survey_Suhelwa_WLS_India/links/6303c829eb7b135a0e53d242/Recolonisation-of-tigers-recorded-from-camera-trap-survey-Suhelwa-WLS-India.pdf
Thapa, K., Manandhar, S., Bista, M., Shakya, J., Sah, G., Dhakal, M., … Karmacharya, D. (2018). Assessment of genetic diversity, population structure, and gene flow of tigers (Panthera Tigris Tigris) across Nepal’s terai arc landscape. PLOS ONE, 13(3), e0193495. doi:10.1371/journal.pone.0193495
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