- A new study in central India looked at how changes in land use patterns and the development of roads are disrupting the genetic connectivity of two large herbivores — gaur and sambar.
- It found that both gaur and sambar responded negatively to land use changes, and the impact was more pronounced in gaur populations.
- The researchers hope that studies like this will help spur evidence-based approaches to maintaining connectivity for multiple endangered species in priority landscapes like central India.
Habitat loss and fragmentation, driven by human activities, have made large mammals highly vulnerable, as they need extensive home ranges, are migratory and have slow reproductive rates. Among the large animals, while the impact on large carnivores often receives attention, herbivores — who play a critical role in ecosystems by controlling wildfires, cycling nutrients, maintaining vegetation dynamics, and serving as the primary food source for carnivores and scavengers — are frequently overlooked. A new study from the National Centre for Biological Sciences (NCBS) is now addressing this oversight.
Set in central India, the study looks at how changes in land use patterns and the development of roads are disrupting the genetic connectivity of two large herbivores — gaur and sambar. The study, published in Molecular Ecology, is among the earliest studies to examine the genetic connectivity of large herbivores at a landscape scale in India.
“Both species are known to be crucial for maintaining carnivore habitats, but unfortunately, they are relatively understudied, especially at the genetic and population genomic levels. Our study focuses on understanding the population structure and connectivity of these species in central India,” says Abhinav Tyagi, lead author of the study and post-doctoral fellow at NCBS.
Focus area
Central India’s forest cover encompasses multiple protected areas (PAs), reserved, and territorial forests. This region faces significant threats from growing linear infrastructure such as highways and railway lines, an expanding road network, as well as changing land use patterns, mining activities, and other development projects. These hinder animal movement, creating fragmented populations confined within small habitat patches. This disconnection in turn disrupts their mating and genetic exchange, increasing the risk of species extinction.
The researchers decided to investigate the genetic connectivity of the gaur and sambar, two large herbivores found in the area. Both species are endemic to South and Southeast Asia, and rank among the top prey species for large carnivores such as tigers. They also have similar habitat association, preferring areas with high tree and shrub densities, and generally avoid anthropogenic disturbances.
The study focused on a landscape spanning the states of Madhya Pradesh and Maharashtra. “We chose central India because the region is well-studied in terms of carnivore connectivity, specifically for tigers and leopards. Our long-term focus is to study the connectivity of multiple species that vary in their ecological traits, such as body size, trophic level, dispersal distance, and social structure. Since connectivity information for carnivores is already available, we looked to quantify the connectivity of large herbivores,” says Uma Ramakrishnan, senior author and professor at NCBS.
The research team collected hundreds of faecal samples of gaur and sambar from several tiger reserves and wildlife sanctuaries, including Kanha, Pench, Nagzira-Nawagaon, Bor, Tadoba-Andhari, Umred Karhandla, and the wildlife corridor between Kanha and Pench. Using Next-Generation Sequencing (NGS), and a combination of population and landscape genetic tools, they investigated whether the species comprised a single contiguous population across the landscape or were fragmented into distinct groups. They also analysed the genetic diversity of gaur and sambar, which is crucial for any species to adapt to sudden environmental changes, diseases, climate shifts, and other stresses. Additionally, they examined natural and artificial landscape features that could hinder animal movement and studied whether gaur and sambar responded differently to those features.
Cause and effect
The study found that both gaur and sambar responded negatively to land use changes, but the impact was more pronounced in gaur populations. The results showed that gaur are highly vulnerable to changes, especially in agricultural areas. In contrast, sambar are more resistant in human-dominated landscapes. However, both species’ movement and gene flow are being affected by the changing landscape.
The findings showed high genetic differences in gaurs, meaning they live in small, isolated populations with little to no gene flow, as seen in Bor Tiger Reserve. These fragmented populations also have low genetic diversity. The researchers were especially concerned about the gaur population in Umred Karhandla Wildlife Sanctuary in Maharashtra.
“We found that the gaur population here shows very high genetic differentiation. Despite not being geographically distant and lying at the centre of three large tiger reserves (Tadoba, Nagzira, and Pench), this population is highly isolated,” says Ramakrishnan. “We believe this is due to the small population size in Umred, which may have led to genetic drift influencing the genetic structure of the gaur population. Additionally, the population is isolated from other gaur populations in terms of movement and gene flow.”
On the other hand, while sambar populations did not show much genetic differentiation, their low levels of genetic diversity are concerning. The researchers speculate that this could be attributed to the large population size of sambar. However, with more data, genetic differentiation may become evident.
The road ahead
This study sheds light on the pressing need for targeted conservation efforts to maintain genetic connectivity and prevent further isolation of herbivore populations in central India. It particularly highlights the urgent need for interventions to protect gaur populations in smaller protected areas like Umred Karhandla Wildlife Sanctuary. Researchers hope that studies like this will help spur evidence-based approaches to maintaining connectivity for multiple endangered species in priority landscapes like central India.
“Monitoring populations, and facilitating and restoring connectivity is crucial, especially for small populations like those in Bor Tiger Reserve and Umred Karhandla Wildlife Sanctuary. Large herbivore populations are becoming increasingly small and isolated, making it imperative to monitor their numbers and connectivity both within and outside protected areas,” says Tyagi.
Ensuring genetic flow and movement between habitat patches will help maintain the genetic diversity necessary for species to adapt to environmental changes and mitigate the risk of extinction.
Banner image: The movement and gene flow of both sambar and gaur are being affected by the changing landscape. Image by Abhinav Tyagi.
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