Advancing evidence-based tiger conservation

In the world’s most populated nation, natural landscapes are dramatically and rapidly being altered by human enterprise. In this context, Pranav Chanchani advocates for data-driven policymaking to sustain tigers in India – encompassing appropriate linkages to information on social and ecological drivers of tiger population. He emphasises developing a nuanced understanding of where and how tigers can be conserved beyond Protected Areas, reconsidering entrenched assumptions about what works for conservation, redefining criteria and milestones for success, and interdisciplinary scientific inquiry.

This post is the third in a three-part series on tiger conservation in India

When we cast an eye over India’s vast tiger landscapes, what do we see? Maps of the species’ occurrence and density that have emerged from the government’s extensive monitoring programme present a complex picture. Areas with tiger presence stand out against an expansive patchwork of forests where the species is absent, which represent over 75% of surveyed habitats. If two key goals of tiger conservation in India are to bring the species back to areas where populations are now locally extinct, and to sustain populations at the highest densities that can be ecologically and socially supported, then the chances of making headway in the next decade can be improved if interventions and planning are strongly data driven. Strengthening the application of evidence-based tiger conservation in India, where nearly 70% of the world’s tigers share space with 1.4 billion people, is also important to effectively manage adverse human-tiger interactions.

In this post, I outline some prominent spatial patterns in the occurrence and density of tigers in India, identify key gaps in our understanding of processes and mechanisms underlying these patterns, and outline how data can be brought to bear in shaping strategies and priorities to advance tiger conservation in multi-use landscapes over the next decade.

Making sense of spatial variation in tiger distribution and density

Across India’s tiger-bearing Protected Areas and reserved forests that collectively hold over 3,600 tigers, there is a 15-fold variation in the species’ densities. A large part of this variation is because not all habitats are equally productive for wild herbivores (tiger prey species such as deer, pigs, antelope, etc.). For example, the forest understory in tropical wet evergreen forests provides less palatable forage for prey relative to forest-grassland mosaics of central India and the terai, where wild ungulates (hoofed mammals) occur at high densities. While habitat productivity sets a ceiling on how many wild herbivores an area can support, realised tiger densities are also determined by human impacts on habitats and corridors – and on the demography, physiology and behaviour of herbivores (and tigers) – in ways that are not always direct or evident. I describe four general sets of patterns in the distribution and density of tigers that are the result of complex interactions between the social and ecological elements of landscapes.

Figure 1. Estimated tiger densities for 101 Protected Areas and reserved forests in India

Note: The following Protected Areas and Reserved Forests Referenced in the post are numbered on the map: 1. Kaziranga Tiger Reserve, 2. Corbett Tiger Reserve, 3. Sathyamangalam Tiger Reserve, 4. Wayanad Wildlife Sanctuary, 5. Ramnagar Forest Division, 6. Ranipur Tiger Reserve, 7. Dholpur - Karauli Tiger Reserve, 8. Palamau Tiger Reserve, 9. Sinilipal Tiger Reserve, 10. Satkoshia Tiger Reserve, 11. Dampa Tiger Reserve, 12. Chandrapur Forest Division.
Abundance has been mapped for sites where density estimates were not available.

Source: Density and abundance estimates used in this map are from Qureshi et al. (2023)

Disclaimer: This map is not a legal description or a reflection of opinion or advice of any nature and does not claim accuracy or representation of the current situation or warrant specification of limitations. The depiction is strictly representational and should not be relied upon. WWF-India shall neither be responsible for this map being misused or misrepresented by a third party/entity, nor be responsible for any damages, consequential losses, costs, expenses incurred basis any action/commission.

First, large tiger populations at high densities occur in areas where prey is both very abundant and widely distributed. There are at least two underlying ecological pre-requisites for these conditions to be met: year-round availability of nutritious forage and vegetation cover across an area; and population growth rates (from birth and immigration) that match or exceed losses (from emigration, or mortality, natural or otherwise). Undoubtedly, these conditions are amply met in about 10 Protected Areas and reserved forests in India, where tigers occur at densities of eight or more per 100 square kilometres (sq. km). Notably, barring Kaziranga National Park, these sites are all ensconced within or connected with larger blocks of tiger habitats.

Second are the 30 or so areas, which hold densities of approximately between two and eight per 100 sq. km. A few variables are very informative about whether these sites are at capacity, or if they have the potential to support higher densities. Key among these are habitat (vegetation, terrain, resource availability) related constraints on herbivore occurrence and densities, which cause species such as sambar and chital to only occur at high densities within ‘pockets’, rather than more widely. Pronounced spatial structure in the wild herbivore densities is often an outcome of the patchy distribution of resources and local hunting, but data on resource distribution and hunting pressure does are very deficient in most contexts – leaving this to be ascertained. Other related variables to scrutinise are survival (age- and sex-specific) rates and other demographic parameters of prey and predator, and relating these to variables like law enforcement monitoring, and structural and functional connectivity with other tiger habitats. Notably, sites like Sathyamangalam Tiger Reserve in Tamil Nadu, Wayanad in Kerala and Ramnagar in Uttarakhand support tigers at densities ranging from four to 11 tigers per 100 sq. km – even as these areas accommodate several thousand human residents. This is to make the case that the relationships between human disturbance and conflict are complex – given that resources (food, cover) are adequate and protection is effective, areas with high levels of human use can also support high tiger densities (Chanchani et al. 2024).

Third are sites where tigers occur at densities below two individuals per 100 sq. km. Such low densities are typically indicative of low prey densities because the habitat is unproductive or unsuitable for gregarious grazing species like chital. This is exemplified by some tropical evergreen forests in southern India, and Himalayan ecosystems. Additionally, in some cases, acute anthropogenic pressure on wildlife (including hunting – whether customary or for illegal trade) and their habitats, that have not been adequately addressed by past and present management, may also be the key drivers. Such low-density tiger habitats do not necessarily lie outside of Protected Areas. Some recently established Tiger Reserves (for example, Ranipur in Uttar Pradeshand Dholpur-Karauli in Rajasthan) and others that are many decades old (for example, Palamau in Jharkhand and Similipal in Odisha) fit within this category.

Finally, the latest iteration of the National Tiger Conservation Authority’s national tiger monitoring exercise in 2022 indicated that about 80% of sampled 100 sq. km grids (surveyed tiger habitats) did not appear to currently support the species. Tigers became locally extinct in these areas for diverse reasons: hunting and persecution (of tigers and their prey), both before and since India’s independence. Hunting pressures were likely exacerbated by progressive habitat fragmentation and degradation in some areas. When tigers have wandered or been translocated into some such areas, like Lalgarh in West Bengal and Satkoshia Tiger Reserve in Odisha, they have been attacked and lynched by local communities for whom memories of living alongside tigers have faded, or because of apprehensions about shifts to tiger-centric forest management. In other areas, where the ecological and social fabric have been eroded by a history of insurgency, wildlife conservation is not an immediate concern. In such areas, tiger population recovery may not be a tenable goal in the foreseeable future, but relevant data can inform strategies to create enabling conditions (both social and ecological) to wildlife and maintain ecosystem integrity over the long term.

Linking patterns to underlying mechanisms

Setting goals for tiger conservation in landscapes, with a focus on sustaining populations in some areas and recovery in others, thus needs to be informed by data on wildlife demography on the one hand, and diverse social and ecological factors on the other. This raises the question: do granular data on tiger and wild herbivore populations and associated factors exist? And if so, are these data consistently and rigorously brought to bear on the conservation of India’s national animal?

The answer is that while extensive data on tiger and herbivore populations and a few relevant habitat variables have been collected through large-scale monitoring exercises, data on social, economic and cultural variables that can affect tiger conservation outcomes are scant. Much more can be done to meaningfully link data on wildlife occurrence and abundance back to management and conservation planning. For example, while the national four-yearly tiger monitoring exercise generates periodic snapshots of population abundance and density, trends in these parameters are not systematically linked back to variables including the spatial variation in the density of wild herbivores, measurements of forage quality and availability, land use change in corridors or to data on the intensity and extent of patrolling by forest guards and beat watchers. Social and human behaviour data on, for example, how people use forests and interact with wildlife, whether they are willing and able to share space with wildlife, and underlying social, economic, cultural and political underpinnings, are all but absent in most contexts.

A result of the patchy application of available ecological and social data is that management and conservation planning are typically only thinly informed by evidence that incorporates complexity and uncertainty. Such evidence is just as relevant to devise appropriate inclusive strategies to bring tigers back to reserves such as Palamau in Jharkhand and Dampa in Mizoram, as it is to inform how human-tiger conflict may be effectively managed in areas like Chandrapur in Maharashtra and the terai in Uttar Pradesh.

The decade ahead

In addition to making evidence more central to conservation planning and decision-making, pivoting to evidence-based tiger conservation will also require rethinking some entrenched assumptions about what works for conservation, recalibrating how success and progress in tiger conservation are typically measured, and devising pathways to integrate local knowledge and understanding with socio-ecological research to plan and set priorities for tiger conservation. To conclude, I briefly dwell on these three dimensions.

First, several entrenched assumptions guide tiger conservation practice. Many of these have some empirical basis, but some such assumptions need to be periodically tested, in the light of newer evidence. For instance, it is commonly assumed that tigers cannot thrive in areas that also accommodate people, and that only inviolate Protected Areas are a panacea for tigers. Undoubtedly, the species populations have dwindled or been precluded from many areas with high human use. Yet, evidence to the contrary is steadily emerging, including about the persistence of tigers in some forests with sizeable human populations and the species’ prolific occurrence along forest edges bordering farmlands and settlements (see, for example, Rayan and Mohamad (2009), Carter et al. (2012), Chanchani et al. (2016), Kafley et al. (2016) and Warrier et al. (2020)). Similarly, it is commonly assumed that rising tiger populations will inevitably lead to marked increases in human casualties, even as attacks on humans are rare events around Tiger Reserves like Kaziranga and Corbett that support the highest densities of tigers globally. It is clear that these assumptions – which are the basis of consequential decisions including conservation zonation and conflict management strategies – need to be rubbed against data to derive insights on mechanisms (both generalisable and context-specific) that drive tiger abundance and persistence and underlie human-tiger interactions.

Thoughtfully re-examining these assumptions will also require collating and generating data on the diversity of forest governance and management structures, and human disturbance regimes under which tigers have persisted. Equally important are investigations of the socio-cultural conditions under which tigers can co-exist with people, and to carefully assess the contributions of other mechanisms that can stress or impact populations. For example, the deleterious impacts of habitat fragmentation, such as large highways cutting across tiger habitats, need to be dexterously teased apart from potential impacts of forest-dependent humans and livestock. Such assessments will encourage broadening approaches and strategies for tiger conservation in areas beyond extant Protected Areas – including, for example, in community-managed forests. They will also reveal where tiger recovery ought not to be the primary conservation focus, potentially opening up important opportunities to focus on other taxa and species, and vital ecosystem processes and services.

Second, even as it is important to hone monitoring programmes that yield estimates of tiger abundance, density and related demographic parameters, equal emphasis is needed on assessing the status of enabling social and ecological conditions required to restore and sustain resilient landscapes that support thriving tiger populations. This will enable us to re-calibrate parameters of conservation success, which are often narrowly centred on tiger numbers. For instance, monitoring the efficacy of invasive species removal and carefully crafting multi-pronged strategies to measure and address change in the illegal and unsustainable hunting of wild herbivores, are critical to understanding progress towards tiger conservation. Ultimately, it will also be important to generate evidence that enables the synergistic management of habitats to support biodiversity and a suite of endangered species. For example, endangered hispid hares, Bengal floricans and swamp deer all rely on alluvial grasslands but may benefit from differing management strategies (such as cutting/burning), without singularly prioritising tigers. All of this can be expedited by establishing systems and processes that make the vast repository of data on wildlife populations and habitats more accessible, while also encouraging interdisciplinary research.

Finally, for evidence-based conservation to be locally appropriate, it needs to be well-aligned with the values, lived experiences, and aspirations of people who share space with wildlife, and also be informed by the experience of forest managers and frontline staff who are intimately familiar with the habitats they are mandated to protect. There are several ways in which such alignments can built. For example, the keen understanding of people living in and around tiger habitats and foresters can inform assumptions and hypotheses, help set and recalibrate conservation targets and enable the filtering of strategies that are better aligned with local or regional priorities that balance concerns of the environment and human well-being. Doing so will be a step in the direction of diversifying solutions and strengthening partnerships for the inclusive stewardship of India’s diminishing natural heritage.

Opinions expressed in this post are that of the author, and may not necessarily be those of WWF-India/their organisation, or of the I4I Editorial Board

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