Browsing by Author "Kher, Varun"

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Dietary habits and competitive interactions of scavenging raptors in the Thar desert
(Wildlife Institute of India, Dehradun, 2025) Shukla, Manas; Kher, Varun; Kolipakam, Vishnupriya
Scavenging raptors, especially vultures, play a crucial role in recycling nutrients and curbing pathogen prevalence in an ecosystem. Their populations in the Indian subcontinent have declined substantially in the past few decades, primarily due to the presence of toxic non-steroidal anti-inflammatory drugs (NSAIDs) in livestock carcasses. This problem worsens for vultures in the Thar desert landscapes, where large numbers of migratory vultures visit in the winter months and increase competition for resident vultures, reducing their access to resources in their critical breeding months. Therefore, understanding their dietary dependence on livestock and their interactions with other scavengers is essential for implementing targeted conservation measures. This study examines the dietary and competitive ecology of White-rumped vulture (Gyps bengalensis), other sympatric vultures, and mammalian scavengers in the Thar Desert, with additional focus on assessing risk from NSAID poisoned livestock carcasses and identifying ecological pressures from carcass use dynamics. For dietary analysis, fecal samples of White-rumped vulture (n = 10) and other migratory vultures (n = 22) of the same foraging guild collected from their identified nesting and roosting sites respectively, and were analysed using DNA metabarcoding to assess dietary composition and overlap. Questionnaires (n = 128) with pastoralists and pharmacy surveys (n = 4) were used to evaluate NSAID usage patterns, along with a geographic hotspot analysis of toxic NSAIDs. Camera traps (n = 34) were opportunistically placed at carcasses to record scavenger presence, feeding time, and aggressive interspecific interactions. Interference and exploitative competition was quantified by developing dominance and efficiency indices, and constructing hierarchies of aggressive dominance and foraging efficiency, followed by the analysis of their ecological predictors using generalised linear models.
Droppings and densities: can sprainting intensity predict otter abundance
(Wildlife Institute of India, Dehradun, 2026) Balaji, Pritham; Pandav, Bivash; Kher, Varun
Reliable estimates of population abundance are fundamental to understand population dynamics and inform conservation management. However, obtaining robust abundance estimates for rare and elusive species remains challenging because rigorous population estimation methods are often not feasible on large scales, require long survey periods, resources and technical expertise. Consequently, wildlife monitoring efforts frequently rely on population indices derived from indirect evidence of the species of interest or proportion of sites occupied. Although the relationship between these indices and population abundance is seldom evaluated. This uncertainty is particularly relevant for otters, which have primarily been studied using their indirect signs which were developed to monitor population status. Smooth-coated otters (Lutrogale perspicillata), a semi-aquatic carnivore for which ecological studies have traditionally relied on indirect signs to study their habitat and diet preferences. Despite its threatened status, there is very little quantitative information on population sizes and trends. This study aimed to estimate the population status of smooth-coated otters inhabiting three Himalayan foothill rivers using multiple complementary approaches and to evaluate whether spraint encounter rates could provide a reliable indication of relative abundance. Camera trap distance sampling, N-mixture modelling based on direct sightings were used to estimate otter populations in each river. Sign surveys were conducted to obtain relative abundance indices such as encounter rates or occupancy probability from each river. By incorporating the use of camera traps, insights into their activity pattern was analysed in these rivers which are outside a protected area that vary in levels of anthropogenic disturbance. The N-mixture model produced highly uncertain abundance estimates because of low detection probability and high variability in count data, indicating that direct-sighting approaches are unlikely to provide reliable abundance estimates for smooth-coated otters under similar field conditions. Camera trap distance sampling generated substantially larger datasets and yielded more precise estimates of detection probability and density, demonstrating greater potential for estimating otter populations. Nevertheless, the number of detections remained insufficient to estimate abundance independently for each river, highlighting the need for increased sampling effort and more rigorous approaches, such as non-invasive genetic approaches or telemetry information, to obtain robust population estimates. Single-season occupancy modelling was of limited value for comparing relative abundance because otters occupied nearly all sampling units within the study area, providing no variation in occupancy estimates between rivers. Similarly, indirect sign surveys for spraint sites failed to show a significant relationship with camera trap encounter rates or estimated population status. Although Khoh exhibited substantially higher camera trap encounter rates than Kolhu, spraint encounter rates showed the opposite pattern, suggesting that sprainting intensity alone is not a reliable proxy for smooth-coated otter abundance in these river systems. These findings support evidence that social behaviour, communal latrine use and habitat-specific detectability can weaken the relationship between spraint site encounter rates and population size. Activity pattern analyses revealed that smooth-coated otters were primarily diurnal and crepuscular. However, otters in the more disturbed Khoh River exhibited a pronounced shift towards crepuscular and nocturnal activity compared with those in Kolhu. This demonstrates the behavioural adaptability of smooth-coated otters to human disturbance in their habitat. Therefore, this study provides one of the first quantitative assessments of smooth-coated otter populations using multiple abundance estimation frameworks in the Himalayan foothills. Although constrained by sample size and limited to two rivers, the study establishes important baseline estimates and demonstrates both the potential and limitations of current monitoring approaches which have been used for other taxa. The findings suggest that camera trap distance sampling currently represents the most promising non-invasive method for estimating smooth-coated otter populations, whereas spraint encounter rates should be interpreted cautiously and not used as a standalone indicator of abundance. Future studies incorporating larger spatial scales, increased sampling effort and rigorous abundance estimation methods will be essential for validating these findings and improving conservation monitoring of this threatened freshwater carnivore.
Effect of land use change on the habitat and abundance of Grizzled giant squirrel in and around Srivilliputhur-Meghamalai Tiger reserve, Srivilliputhur Division, Tamil Nadu
(Wildlife Institute of India, Dehradun, 2024) Bevoor, Shilpa; Gopi, G.V.; Kher, Varun; Goyal, S.P.
Human activities, especially energy extraction and food production, have drastically altered the global environment, impacting many wild species. Since 1990, around 420 million hectares of forests have been lost mainly due to agricultural conversion, significantly affecting biodiversity. In biodiversity hotspots like India's Western Ghats, agricultural expansion, monoculture plantations (tea, coffee, rubber), and non-timber forest product harvesting have fragmented protected areas, altered plant communities, disrupted nutrient cycles, and reduced carbon sequestration. While monoculture plantations reduce biodiversity, they can still provide habitats for some threatened species. Wildlife such as nilgai, blackbuck, elephants, and giant squirrels in India have adapted to these altered landscapes for food, water, and shelter, demonstrating resilience amidst habitat changes. This study focuses on the impact of converting barren lands into mango and coconut plantations around the Srivilliputhur-Megamalai Tiger Reserve in southern India on the grizzled giant squirrel population and habitat. Over the past three decades, these changes have enhanced connectivity between natural forests and agricultural areas, offering energy-rich fruits that attract wildlife, including GGS. This shift has altered ecological dynamics, making wildlife more reliant on cultivated foods and affecting their movement patterns. Density estimates reveal higher concentrations of GGS and nesting sites (dreys) in plantations compared to protected areas, with mixed plantations showing the highest densities due to the availability of nesting sites and year-round fruiting trees. Seasonal variations in GGS distribution highlight preferences for specific tree species based on fruit availability and habitat characteristics. The study also examines drey site preferences, noting GGS preference for mango trees in plantations over coconut trees due to structural attributes that provide better support and protection. These findings underscore the species' adaptation to plantation environments while emphasizing the critical role of specific habitat features for nesting and overall habitat suitability. Local farmers report conflicts with GGS due to crop damage, particularly affecting coconut, mango, tamarind, and other fruit-bearing trees. Perceived economic losses from GGS feeding habits often exceed actual damage levels, emphasizing the need for accurate assessment and targeted mitigation strategies to reduce conflict. Conservation implications stress the importance of maintaining critical habitats within protected areas, establishing buffer zones between plantations and natural forests, and promoting biodiversity-friendly practices in monoculture plantations. Community-based conservation efforts and adaptive management strategies are essential for mitigating human-wildlife conflicts and ensuring the sustainable coexistence of GGS and agricultural livelihoods in this biodiversity hotspot
Heat Hardening and the Influence of Thermal Heterogeneity of Habitat on Aboveground Activity in Spiny-tailed Lizard (Saara hardwickii)
(Wildlife Institute of India, Dehradun, 2025) Vassa, Chirag Nimish; Dutta, Sutirtha; Kher, Varun
Human induced climate change has challenged the persistence of many organisms at different biotic levels and alter their interaction with the environment. Ectotherms are particularly vulnerable to anthropogenic climate change due to their reliance on external environment for various life history traits. Thermoregulatory behaviour is often used by many ectotherms especially reptiles to regulate their body temperature and will be crucial in imminent future with intensification of climate change. Although behavioural thermoregulation is widely studied, but studies looking at influence of thermal heterogeneity of a habitat on aboveground activity is limited. Moreover, with escalation in global warming ectotherms might have to rely on another mechanism in addition to thermoregulatory behaviour to combat the effect. One such physiological mechanism is heat hardening a quick response to thermal tolerance that temporarily enhances thermal tolerance, allowing lizards to withstand greater temperatures for a short period. Despite its importance very limited data is available for heat hardening capacity in reptiles. This study examined the influence of thermal heterogeneity of a habitat on aboveground activity in spiny-tailed lizard (Saara hardwickii) and assessed their heat hardening capacity. Additionally, trade-off hypothesis was also tested which has been recently proposed to explain the dynamics of thermal tolerance plasticity. I found positive influence of habitat heterogeneity on aboveground activity of the lizard. However, individuals in both the conditions spent similar amount of time in different behaviours. With respect to phenotypic plasticity i.e. heat hardening, I did not find any evidence of thermal tolerance plasticity during my experimental trials but few individuals did show increased thermal tolerance implying intraspecific variation. Additionally, the results from heat hardening experiments found no support for trade-off hypothesis. My study underscores the importance of habitat heterogeneity for species like spiny-tailed lizard which thrives in extreme temperatures. Furthermore, Lack of phenotypic plasticity in thermal tolerance increases it’s risks to overheating and dependency on behavioural thermoregulation.
Leveraging citizen science for bird monitoring: A case study assessing the impacts of urbanization on bird assemblages of the Nilgiris
(Wildlife Institute of India, Dehradun, 2024) Phinehas N, David; Kher, Varun; Robin, V.V.; Jha, Ashish
Anthropogenic alteration of habitats is the leading cause for biodiversity loss across the world. To accommodate the ever increasing human population, intensification of urbanised areas have led to the most extreme forms for habitat alteration (Batáry et al., 2018) and imposes a unique set of ecological filters. 2. Over that last 2 centuries during the colonial past, the Nilgiris has witnessed large-scale change in the landscape structure from native shola-grassland matrix to extensive tea and eucalyptus plantations. Currently it has emerged into a tourist haven, attracting millions every year, leading to expansion of the urban cover to accommodate the growing demand. 3. This study illuminates the profound effects of urbanization on bird communities in the Nilgiris, showcasing how habitat transformation alters community parameters such as, species richness, abundance, and composition. My results indicate a stark pattern: as urbanization intensifies, species richness declines, while a select few generalist species thrive in high abundance. 4. My findings reveal that settlements and proximity to remnant shola patches are the primary factors influencing avian community structure. Areas with higher settlement percentages and greater distances from shola patches exhibit reduced species richness and diversity. In contrast, less urbanized areas, closer to natural habitats, maintain higher biodiversity. This aligns with the hypothesis that urban environments simplify habitat structures, creating 'filter' that only a limited number of species can pass through, thereby fostering biotic homogenization. 5. Urban generalists, such as the House Sparrow, Rock Pigeon, and House Crow, flourish in highly urbanized zones due to their ability to exploit the abundant food resources and nesting sites provided by human activities. These species benefit from the homogenized urban landscape, which offers ample opportunities for foraging and nesting, often at the expense of more specialized species. Conversely, endemic shola forest specialists, such as the Nilgiri Laughing thrush and the Black-and-orange Flycatcher, suffer due to their stringent habitat requirements and limited dispersal abilities. These findings highlight the ecological trade-offs imposed by urbanization, where habitat degradation and loss disproportionately impact species with narrow niche widths. 6. This study also highlights the usefulness of citizen science as a tool for collection of largescale data in a short time span. I also tested for the accuracy of the citizen science data against a research-grade benchmark, ie, data collected by me. The results suggest that no significant variations were detected between the two datasets. 7. Conservation Implications: Monitoring species with vulnerable traits to keep track of further degradation of the habitat and involvement of the local citizens is needed. The study highlights a critical need to preserve remaining shola fragments and implementation of biodiversity friendly urban planning.
Patterns of Bird Community Structure in Relation to Land-Use Driven Habitat Changes in the Arid Grasslands of Thar Desert
(Wildlife Institute of India, Dehradun, 2019) Kher, Varun; Dutta, Sutirtha; Uniyal, V.P.; Page, Navendu V.
The Indian Thar desert has seen a massive loss of grassland habitat in the last few decades. The main driver of this habitat loss has been the large-scale change in landuse from pastoralism to agriculture, leading to expansion of cultivated land over grasslands. This expansion, further compounded by a simultaneous rise in livestock population has drastically increased grazing pressure on the remaining rangelands. To complicate things further, irrigation schemes (notably the Indira Gandhi Canal) have led to intensification of agriculture in many areas. Protected area network in this landscape is minimal and ineffective, making the multiple-use agro-pastoral landscapes very important for conservation of wildlife. The largest protected area in the landscape – the “DNP WLS” – is also a multiple-use landscape and home to more than 50k people whose livelihood is tied to the federal mandate of conservation in the sanctuary. 1. Understanding the impact of land use change on native biodiversity is thus very important for conservation of biodiversity in this critical habitat. In this context, my study tries to find effects of land-use change on community structure of birds in the arid grassland of Jaisalmer district in the Thar Desert. 2. Understanding ecology or distribution and abundance of species is incomplete without holistically understanding the patterns and processes occurring at the community level. To this end, I explored the patterns of bird community structure in the Thar Desert and tried to understand how these properties change with land-use driven habitat change, by comparing fundamental properties of biological communities like species richness, abundance and composition. Additionally, I tried to find out potential habitat correlates of these properties, so as to shed some light on the processes that might be driving community assembly in response to land-use change. 3. Bird community structure: My results indicate that local-scale species richness,abundance and composition did not differ significantly between protected grasslands, rangelands and extensive rain-fed croplands, during either of the seasons. However, intensive irrigated croplands had a notably different community structure with higher species richness and abundance, during both winter and summer. The change is community structure of intensive croplands was influenced by the change in native species along with ingression of newly colonised species. Most of the newly colonised species were restricted to areas with intensive agriculture where their survival was potentially facilitated by the new microhabitats created by irrigation and associated changes (Rahmani & Soni, 1997). 4. Regional species pool: Intensive agriculture increased the overall species of birds in the region by sustaining newly colonised bird species; while the number of native species in this pool was only marginally lower than protected grasslands and comparable to all the other land-uses in both the seasons. Considering both the seasons together, protected grasslands had the highest naïve and estimated number of native species while the naïve and estimated number of native species in other three land-uses – Rangelands, extensive croplands and intensive croplands – was only marginally lower. This signifies that most species found in the region can use the entire gradient of land-use types at their current levels of intensification. Although this result by itself does not indicate that, all land-use types can sustain all the native species. 5. Seasonality of patterns: In winter, protected grasslands, rangelands and extensive croplands had similar bird communities, which together were significantly different from the communities in intensive croplands. The same pattern repeated in summer, but the magnitude of difference between bird communities in intensive agriculture and other land-uses was much lower. This pattern was correlated to the pattern shown by vegetation structure of intensive agriculture, which also became more similar to other land-uses after harvesting of crops in the summer. This potentially suggests that bird communities are influenced by vegetation structure and areas with similar vegetation structure would have similar bird communities. 6. Habitat correlates of species richness and bird community composition: In both the seasons, species richness was positively associated with the foliar volume of woody vegetation and negatively associated with forb volume (which in turn was negatively correlated with grass volume). During winter, species richness was positively related to crop volume and during summer, with compositional diversity of vegetation. Community composition like richness was influenced significantly by woody plant foliar biomass in both the seasons. Crop volume also had a significant influence on bird communities during both winter and summer, whereas grass volume was significantly influential only in winters. Conservation implications: This study corroborates many others in indicating that low-impact land-uses are important secondary habitats for conservation of grassland species (Dutta & Jhala, 2014; Wright, Lake, & Dolman, 2012). The inferences further support the commonly advocated approach of conserving grasslands at a landscape scale by strategically placing them as mosaics of low-impact agro pastoral land-use with small protected areas embedded within them (Dutta & Jhala, 2014; Dutta, Rahmani, & Jhala, 2011; Singh et al., 2006).
Population and behavioural responses of rodents and reptiles to woody encroachment in the Thar desert
(Wildlife Institute of India, Dehradun, 2026) Pawar, Himani; Dutta, Sutirtha; Kher, Varun
Woody encroachment is increasingly modifying open ecosystems worldwide, often altering trophic-level interactions and species composition. In the Indian Thar Desert, Calotropis procera is rapidly expanding across grassland and scrubland habitats, but its ecological consequences for desert fauna remain poorly understood. This study assessed the effects of varying levels of Calotropis procera encroachment on habitat structure, predation pressure, and behaviour and abundance of nocturnal rodents and two diurnal lizard species in and around Desert National Park, Jaisalmer. Field surveys were conducted across no, moderate, and high encroachment levels of C. procera during 2025–2026. Responses of nocturnal rodent community were assessed through burrow counts and giving-up density (GUD) experiment. Reptile responses were assessed through abundance surveys and flight-initiation distance (FID) experiment, and clay model experiment was designed to quantify predation pressure. Rodent abundance, measured through active burrow counts, declined from no encroachment plots to moderate and high encroachment levels. Conversely, giving-up density at artificial food patches was greater in no encroached plots - indicative of greater predation risk perception - compared to moderately and highly encroached habitats. Lunar illumination interacted with encroachment level to influence rodent foraging decisions, indicating the role of habitat structure and environmental conditions in shaping behavioural responses to predation risk. Reptile species exhibited contrasting responses to woody encroachment. Acanthodactylus cantoris showed declines in abundance with increasing encroachment. Behavioural response mirrored this pattern. Flight-initiation distance of Acanthodactylus cantoris decreased substantially with increasing encroachment. In contrast, Trapelus agilis occurred at higher densities in highly encroached areas than non-encroached areas and its FID was primarily influenced by refuge availability and starting distance rather than encroachment level. Predation-risk experiment revealed context-dependent effects of encroachment. In scrubland habitat, predation was faster in moderate and high encroachment plots than in no encroachment. Habitat influenced predation pressure too, as clay models faced higher predation rate in grassland than scrubland. This study demonstrates that woody encroachment produces species-specific ecological consequences, and continued expansion of Calotropis procera has the potential to reshape community composition through behavioural responses and trophic interactions, in the Thar Desert. Management interventions aimed at maintaining and preserving open habitats may therefore be important for conserving faunal diversity in this important conservation ecosystem.