Theses and Dissertations

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Author: search.filters.author.Kher, VarunStart date: 2024

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    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.
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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.
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    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
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    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.