One of India’s most important biodiversity hotspots, Manas National Park and Tiger Reserve's resilience is a reflection of effective conservation policies, anti-poaching efforts, and strong governance which drove the recovery of endangered species in protected areas (PAs), said the study titled ‘Status of Endangered Large Prey Predators Following Civil Unrest in a Biodiversity Hotspot of India’, published in scientific journal Nature.
Situated within the Bodoland Territorial Area Districts of Baksa and Chirang in Assam, the Manas TR is spread over 2,837 sq km with a 500 sq km core. Serving as an important transboundary conservation landscape spanning north-eastern India and southern Bhutan, it is recognised for its biodiversity and holds multiple designations including UNESCO World Heritage Site.
Sharing its northern boundary with the Royal Manas National Park and Phibsoo Wildlife Sanctuary in Bhutan, the TR connects to Buxa in West Bengal to the west and is linked to Jomotsangkha Wildlife Sanctuary in Bhutan to the east. The transboundary landscape spans approximately 8,000 sq km across north-eastern India and southern Bhutan.
Located at the confluence of the Indo-Burma and Eastern Himalaya, Manas suffered extensive damage during civil unrest from the late 1980s to early 2000s which led to widespread habitat destruction, poaching and a collapse of its ecological management systems.
The study noted that forest personnel and facilities were targeted by armed rebels leading to deterioration of park management. Uncontrolled human access to the park added biotic pressure leading to massive land use change and habitat degradation. During this period, over 40 per cent of the primary forests were converted to agriculture and settlements.
The period saw a drastic decline in populations of flagship species including local extinction of the greater one-horned rhinoceros and the near extermination of tuskers due to organized poaching and ivory trade. The populations of the endangered eastern swamp deer also nearly extirpated during the conflict. Spotted deer and wild boar population also dwindled due to their high value as bushmeat.
However, following the resolution of civil unrest in 2003, there has been an encouraging recovery of tigers, leopards and several other wildlife species in the protected habitat, revealed the study carried out by Vaibhav Chandra Mathur, Jayanta Kumar Bora, Jyotishman Deka, Deb Ranjan Laha, Keshab Gogoi, Qamar Qureshi and Ujjwal Kumar during 2022–2023.
The study used elephant-back line transect distance sampling and camera trap-based spatially explicit capture-recapture techniques to assess the post-conflict recovery of endangered prey-predator guilds in the TR and found that habitat restoration, anti-poaching initiatives and community engagement programmes, initiated to restore Manas’ ecological integrity, gradually led to the recovery of several species.
A total of 50 spatial transects covering 408 km in 2022 and 51 transects covering 694 km in 2023 were walked to estimate ungulate densities. The 267 camera trap stations deployed helped detection of 57 tigers—26 female, 23 male and 8 unsexed—along with 38 leopards. The tiger density was found to be 7.91 per 100 sq km.
“The recovery of the tiger population in Manas, at a growth rate of 17 per cent annually, is driven by enhanced protection measures such as improved law enforcement and increased prey availability. With 57 adult individuals, including more than 20 breeding females, Manas serves as a critical source population for the transboundary Manas-Dooars landscape,” the survey underlined.
The study recorded high density of elephant (9.14 per sq km) and wild buffalo (4.47 per sq km). Leopards maintained a stable density of 4.77 per 100 sq km. Other species like gaur, sambar and barking deer showed stable density compared to 2015 baselines. Reintroduction of the rhinoceros in 2008 and the swamp deer in 2014 saw their population grow at a rate of around 17 per cent annually, marking a significant progress in restoring Manas’ biodiversity.
The survey, however, revealed decline in hog deer and wild pig populations and suggested persistent ecological vulnerabilities despite broader ecosystem recovery. The authors cautioned that umbrella species conservation approach, where recovery of the apex species is often evaluated as recovery of the overall ecosystem in India, may not always address the needs of habitat specialists.
The sharp decline of hog deer, for instance, calls for species-specific management such as translocation from more stable populations in Kaziranga and Orang Tiger Reserves and the establishment of predator-proof enclosures, they underlined.
Additionally, they stated that the continued decline of wild pigs, an important prey base for large carnivores, highlighted the need for intensified habitat protection and prey base restoration.
The researchers demonstrated that elephant-back line transects, instead of foot transects in tall grassland habitats, can effectively estimate the density of ungulates and mega herbivores and suggested that given the habitat complexity and northeast India’s strategic positioning in a biodiversity hotspot, the approach can be extended to other floodplain ecosystems to assess the abundance and distribution of ungulates and mega herbivores with more accuracy.