- A study across five tiger reserves in India found that the big cats exposed to higher levels of tourism and other human disturbance had elevated stress hormone levels.
- Female tigers appeared to favour less disturbed areas for breeding, although the researchers caution that the findings show associations rather than cause and effect.
- The authors recommend improving wildlife tourism management, including limiting safari vehicles and reducing crowding, while emphasising that tourism and the revenue it generates remains important for conservation.
India’s tiger reserves have become both conservation success stories and tourism magnets. Every year, thousands of safari vehicles enter India’s protected forests, generating revenue for conservation and local communities. But a recent study suggests that this growing human footprint may also come at a physiological cost for the country’s national animal, and may even influence where female tigers establish breeding areas.
“Wildlife tourism is growing rapidly around our protected areas. It funds conservation, but more people also means more stress for the animals,” says Govindhaswamy Umapathy, chief scientist at the Laboratory for the Conservation of Endangered Species, CSIR-Centre for Cellular and Molecular Biology, and the study’s corresponding author. “Earlier Indian studies looked at just one or two reserves and focused on stress. We wanted the full picture across the country, not only where tigers are stressed, but where tigresses choose to breed,” he adds.
However, industry experts also caution against treating tourism as a bigger threat than habitat loss or large-scale development pressures.
Tracking stress without disturbing tigers
The study was conducted between November 2020 and February 2023, in five tiger reserves: Corbett Tiger Reserve in Uttarakhand, Tadoba-Andhari Tiger Reserve in Maharashtra, Kanha Tiger Reserve and Bandhavgarh Tiger Reserve in Madhya Pradesh, and Periyar Tiger Reserve in Kerala.
The choice of reserves was deliberate. “We picked the five reserves that between them cover very different tiger densities, habitats and tourism styles, including Periyar’s year-round boat tourism. That range is what makes the findings national rather than local,” Umapathy says.
Rather than capturing or collaring tigers, the researchers used a non-invasive approach. They collected 728 scat samples across tourism and non-tourism periods. Genetic analysis confirmed that 610 belonged to tigers. Of the genetically sexed samples, 185 were from males and 291 from females. The researchers then measured faecal glucocorticoid metabolites, a widely used indicator of physiological stress, in all tiger-positive samples, and analysed faecal progesterone metabolites in female samples to assess reproductive activity.
The researchers first compared hormone levels across tourism and non-tourism periods, core and buffer zones, seasons and areas experiencing different levels of human disturbance. They then used statistical models to examine how tourist vehicle numbers, anthropogenic activity, reserve zones and distance from tourism roads, villages and water bodies influenced stress levels, while also testing how these factors interacted.
“We were careful not to blame everything on tourism. For each of the 610 confirmed tiger samples, we recorded the different pressures separately — the number of tourist vehicles that day, how close we were to a tourism road, to a village, to water, and whether there was grazing, farming or tree-lopping nearby — and then tested them against each other in the models,” says Umapathy. This allowed them to see distinct patterns. Stress rose specifically with tourist vehicle numbers and close to tourism roads. It also rose, separately, with year-round pressures like cattle grazing. “Comparing tourism and non-tourism seasons, and core versus buffer zones, let us pull the tourism signal apart from the rest,” he adds.
Human disturbance associated with higher stress
The clearest finding was that tigers exposed to higher levels of human disturbance, including tourism, livestock grazing, agriculture and habitat degradation, showed elevated stress hormone levels.
Across the reserves, stress hormone levels were generally higher during the tourism season than during periods when tourism was absent or reduced. Tigers also experienced higher stress in areas with more tourist vehicles, greater anthropogenic activity and closer proximity to tourism roads and villages. Overall, tigers in buffer zones had higher stress hormone levels than those in core areas, reflecting greater levels of human activity. However, the researchers also found that tigers in core zones became particularly sensitive when tourism or other disturbances occurred there, suggesting these normally quieter habitats may act as important refuges from human disturbance.
Core-zone tigers also reacted more sharply to disturbance than buffer-zone tigers. “Animals in the buffer live with people all year, so they’ve grown used to it, but a tiger in the core is hit hard by a sudden burst of tourism,” says Umapathy. He adds that Corbett was an exception to this pattern, with tigers in the core showing higher stress, which the researchers attributed to unusually high tiger density and competition rather than tourism.
Disturbance may influence breeding
By comparing reproductive and stress hormone levels, the researchers found that potential breeding locations for female tigers generally occurred in areas where they experienced relatively low stress. Across the five reserves, potential breeding hotspots and high-stress locations were mostly separate, although there were some overlaps.
“Tigresses showed higher reproductive hormone levels exactly where their stress levels were lowest, and on our maps the breeding areas sat apart from the disturbed areas. In other words, females seem to seek out calm pockets to breed. That worries me, because if disturbance keeps creeping into those quiet refuges, we lose breeding habitat even in forests that still hold tigers,” says Umapathy.
The authors, however, caution that potential breeding locations were inferred from hormone patterns rather than direct observations or GPS tracking of individual tigers. The findings show associations rather than proving that tourism directly causes higher stress or determines where females choose to breed. They note that factors such as tiger density and prey availability could also influence hormone levels, and recommend future studies that track individual animals over time to better understand how human disturbance affects stress and breeding behaviour.
Implications for tourism
The study does not argue against wildlife tourism. Instead, it recommends managing tourism more carefully to minimise disturbance in ecologically sensitive areas. The authors recommend limiting the number of safari vehicles entering reserves, preventing vehicle crowding at tiger sightings, shortening safari duration, strengthening protection in heavily disturbed buffer zones, and minimising disturbance in areas that may be important for breeding.
The findings should also be viewed in the broader context of the many pressures facing India’s tigers. “Wildlife tourism, despite its drawbacks, is one of the few industries that can coexist with nature. Mining, roads, urbanisation and other forms of infrastructure development have a far greater impact on tiger habitats, while tourism can generate revenue and incentives that support forest protection and wildlife conservation,” says Anish Andheria, president and CEO of the Wildlife Conservation Trust. He is not associated with the study.
Umapathy suggests trimming the morning and evening safaris by about an hour and guard core zones, because these serve as important refuges. Buffer management, including patrolling, controlling grazing and preventing tree lopping in reserves such as Tadoba and Bandhavgarh, should also be strengthened, he notes. “Train and empower safari drivers to follow ethical rules and end the practice of paying for guaranteed sightings. And monitor stress and breeding hormones every year, so we know where the tigresses are breeding and can quietly keep tourists out of those areas at the right time. Done well, tourism and tiger reproduction can coexist,” says Umapathy.
Tourism should continue to evolve to minimise disturbance while ensuring that local communities remain among its primary beneficiaries, Andheria notes. But he cautions against treating it as a greater conservation concern than habitat loss, fragmentation and other large-scale development pressures.
Banner image: A tiger walks past a vehicle carrying tourists in Ranthambore National Park in 2010. (AP Photo/ Mustafa Quraishi, File)
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