How Many Tigers A Forest Can Hold
Preliminary findings of a study by the Wildlife Institute of India (WII) suggest that the density of tigers in the Sunderbans may have reached the carrying capacity of the mangrove forests, leading to frequent dispersals and a surge in human-wildlife conflict. Availability of food and space is the primary factor that determines how many tigers a forest can hold. And often, food is space for the tiger.
In the Terai and Shivalik hills habitat — think Corbett tiger reserve, for example — 10-16 tigers can survive in 100 sq km. This slides to 7-11 tigers per 100 sq km in the reserves of north-central Western Ghats such as Bandipur, and to 6-10 tigers per 100 sq km in the dry deciduous forests, such as Kanha, of central India. The correlation between prey availability and tiger density is fairly established. There is even a simple linear regression explaining the relationship in the 2018 All-India Tiger report that put the carrying capacity in the Sunderbans “at around 4 tigers” per 100 sq km. A joint Indo-Bangla study in 2015 pegged the tiger density at 2.85 per 100 sq km after surveying eight blocks spanning 2,913 sq km across the international borders in the Sunderbans. The ongoing WII study indicates a density of 3-5 tigers in the Sunderbans. Given that 88 (86-90) tigers were estimated in 2,313 sq km of the Sundarbans in 2018, the population has been close to its so-called saturation point in the mangrove delta for some time.
The Sunderbans, the world’s largest mangrove delta which is home to Royal Bengal Tigers, is spread across 10,000 sq km. More than 4,000 sq km is in West Bengal and the rest in Bangladesh. The Indian Sunderbans is split between the tiger reserve and populated pockets of South 24 Parganas. In the Bengal part, around 1,500 sq km of Bengal’s mangrove delta covers populated areas. In the 2014 national census, 76 tigers were traced in the zone. In 2018, the number of big cats was 88. The 2020-2021 Census conducted by the state forest department had found 96 tigers in the delta. The 2022 national census started in the first week of December.
The “peak density” of a forest is dependent on several parameters, such as prey base, human interference, and the male-female ratio of tigers. The mangrove delta has been ravaged by a welter of developments. The pandemic is said to have resulted in a manifold increase in human interference. The parameters have changed over time. There is no reason to believe that the parameters in 2022 should be the same as in 2018. Hundreds of thousands of villagers, who used to work in Bangladesh, have come over to the Sundarbans. To many or the most, the loss of livelihood has forced them to switch over to forestry in search of fish and crabs. Since 2020, more than 30 people have been killed in attacks by tigers. In many cases, villagers enter forests after breaching the nylon nets that mark their boundaries. Nonetheless, the forests with low density of the big cat population are said to be the “best possible option to curb the man-animal conflict”.
Artificially boosting the prey base in a reserve is often an intuitive solution but it can be counter-productive. While tackling external factors, such as bushmeat hunting, is necessary to ease pressure on the tiger, the government’s policies have discouraged reserve managers from striving to increase tiger densities by artificial management practices of habitat manipulation or prey augmentation. To harness the umbrella effect of tigers for biodiversity conservation, experts say, it is more beneficial to increase areas occupied by tigers. For many, the prescription is to create safe connectivity among forests and allow tigers to disperse safely to new areas. But though vital for genes to travel and avoid a population bottleneck, wildlife corridors may not be the one-stop solution for conflict.
However, as several studies have shown, removing tigers or any wildlife cannot eliminate the chances of future interface as another lot invariably turns up. The remedy, experts say, lies in smarter land use to minimise damage and adequate incentives to promote acceptance of wildlife. Generous compensation policies can take care of the financial cost of losing livestock or crops, or wasted man hours when a workplace is avoided due to a passing tiger. Besides, the percolation of financial benefits of having charismatic wildlife in the neighbourhood can also nudge some towards better tolerance.
Ultimately, it is the people of the Sunderbans who will decide how many tigers can be accommodated in their neighbourhood. In a landscape squeezed in by climate change, rising sea level and salinity, their future is nearly as precarious as the tiger’s. It is for the policymakers to give them enough reasons to make a balanced choice.