- Scientists analysed tiger faecal samples from five reserves and found that each population carries a distinct gut microbiome.
- Microbial communities varied with season and with levels of human disturbance between core and buffer zones.
- Researchers say gut microbes could become a non-invasive early indicator of environmental pressure on tiger populations.
On a cold morning in Corbett Tiger Reserve, a team from the CSIR–Centre for Cellular and Molecular Biology (CCMB) walked through the dense forest in search of fresh pugmarks. They were not tracking the tiger itself, but what it had left behind. The team collected similar faecal samples in Kanha, Bandhavgarh, Tadoba–Andhari and Periyar tiger reserves. Together, these samples showed the hidden microbes living inside the cats — their gut microbiome.
The researchers compared the gut bacteria of Bengal tigers across the multiple Indian reserves. In their new study, published in Global Ecology and Conservation, they explored whether human activities in tiger habitats leaves measurable traces inside the animals. Habitats and seasons can influence the bacterial community structures in the tiger, with potential implications for its health, the study found.
“Tigers in buffer zones experience more human and livestock presence compared to those in the core areas. We wanted to see if this difference is reflected in their gut microbes,” said Govindhaswamy Umapathy, chief scientist at the Laboratory for the Conservation of Endangered Species (LaCONES) and principal investigator of the study.
Microbial differences across reserves and seasons
Gut microbes play vital roles in digestion, immunity and disease resistance. A balanced microbial community supports health, while an imbalance can make animals more vulnerable to stress or illness.
Over two years, researchers collected faecal samples from five tiger reserves to assess how gut bacteria varied by location, season and disturbance. They used the technique, DNA metabarcoding to sequence the bacteria in the sample and catalogued thousands of bacterial species.
The results indicate that tigers in each reserve carried distinct microbial communities. Bandhavgarh tigers had distinct bacterial communities, while Kanha and Tadoba showed more similarity to each other. Seasonal shifts were also notable, with monsoon and winter samples differing significantly, possibly due to changes in prey and environmental conditions.
Across all samples, 36 bacterial genera formed the “core microbiome” typical of wild carnivores: groups such as Proteobacteria, Firmicutes, Bacteroidota, Fusobacteriota and Actinobacteria. Yet each reserve displayed its own microbial fingerprint — Bandhavgarh with more Bacteroides, Kanha and Periyar with higher levels of Fusobacterium.
Buffer zones around tiger reserves often overlap with villages and grazing lands where people, livestock and tigers share space. These interactions can introduce new bacteria or stressors. “We found variation in microbial diversity between disturbed and less disturbed habitats, but more detailed work is needed to understand the specific causes,” Umapathy said.
Similar trends across the border
Dibesh Karmacharya, wildlife geneticist and executive director of the Center for Molecular Dynamics Nepal, who was not involved in the research, called the study significant and said, “This study adds value by contributing to important gut microbiome and health baseline information for tigers from India.”
Karmacharya was involved in similar research from Nepal that supports the trends seen in this CCMB study from India. In 2019, he and his colleagues profiled the gut bacteria of 32 Bengal tigers from Chitwan, Bardia and Suklaphanta. The team found that tigers in more disturbed parks like Chitwan had higher microbial diversity compared to isolated populations in Suklaphanta. “The microbiome patterns (of the Indian tigers) reflected what we had already seen in tiger genetics,” Karmacharya said. “Populations that were genetically connected had similar microbes, while isolated ones showed distinct bacterial profiles.”
The CCMB team used computational tools to predict microbial functions. Some bacteria aided digestion and vitamin production. Others were associated with breaking down industrial pollutants such as hydrocarbons.
“In Tadoba, where there are coal mines and power plants nearby, we found bacterial groups known to break down hydrocarbons,” Umapathy said. A similar trend appeared in Nepal’s Chitwan, where microbial pathways suggested exposure to environmental chemicals.
For Karmacharya, this points to a broader role for gut microbes: “The microbiome acts as an early-warning sensor. It tells us about exposure and stress long before visible signs appear.”
In their study, the CCMB researchers note that such microbial shifts could also become valuable, non-invasive indicators of habitat disturbance. Changes inside the gut may reveal stress, poor diet or environmental contamination before they manifest in behaviour or population decline.
Karmacharya underlined the stakes: the gut microbiome “plays an important role in the overall health of mammals, including tigers, and therefore their long-term survivability.” Human activities, he noted, can alter this balance. “Land conversion, habitat encroachment and exposure to human settlements or animal production sites near tiger habitats can greatly influence and eventually alter the gut health of tigers and hence their overall health. Therefore, a good and effective buffer around protected habitats can help maintain tiger gut microbiome health — conservation of gut microbiome equals conservation of the species.”
Both the Indian and Nepali studies, however, relied on 16S rRNA analysis, which offers limited resolution. As Karmacharya cautioned, “Reliance on predictive rather than empirical functional data means that pathways were inferred rather than directly measured. Future studies using metagenomics or metabolomics will provide a more complete picture.”
Earlier evidence of rising stress
The new microbiome findings build on previous work by Umapathy’s team. In 2019, they examined tiger stress in Kanha and Bandhavgarh by measuring faecal glucocorticoid metabolites (fGCM). They collected samples from tourist-heavy zones and quieter areas, and repeated the work during the monsoon closure.
They found a clear pattern: stress levels were higher during tourism season and increased with the number of safari vehicles. Human and cattle movement also pushed hormone levels up. The study indicated that tourism, even when carefully managed, can add significant pressure on tigers already coping with fragmented, human-dominated landscapes.
For conservation managers, these internal markers may provide an early signal of how well big cats are coping in shared and changing landscapes.
Read more: Tracking tigers as they move from comfort zones to independence
Banner image: A tiger attempts to find its way through a throng of safari vehicles in Ranthambhore Tiger Reserve. Human disturbance can shift prey availability and diets, which in turn affects the gut microbiome of wild tigers. Image by Vanished2009 via Wikimedia Commons (CC BY-SA 4.0).
