Browsing by Author "Dutta, Sutirtha"

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Drivers of community and functional assemblages in rocky intertidal ecosystems of the Goan coast
(Wildlife Institute of India, Dehradun, 2026) Prashant, Shreyas; Ghanekar, Chinmaya; Dutta, Sutirtha; Johnson, J.A.
Rocky intertidal ecosystems have long served as natural laboratories for testing fundamental ecological theories. However, much of our understanding of community assemblages in these systems comes from temperate shores. In contrast, tropical intertidal ecosystems remain largely understudied. The disparity in environmental conditions between the temperate and the tropical zones limits our understanding of ecological processes. Therefore, investigating how environmental and biotic factors drive tropical community assemblages is critical for assessing the generalizability of existing ecological theory. This study examines the effects of environmental stress gradients ranging from the upper to the lower intertidal zones on community and functional assemblages in Goa’s rocky intertidal ecosystem. The influence of predation on community composition is also investigated within this ecosystem. To understand the effects of the environmental stress gradient and multiple fine-scale habitat characteristics on the community, a transect-quadrat method was employed across three study sites. The environmental stress gradient was found to be the main factor influencing community composition and structure, while sand cover, wave action and substrate complexity operated at finer scales within the broader gradient. Functional traits were compiled for the organisms found within the quadrats. This trait matrix was then used to assess whether motile and sessile animals respond differently to gradients of environmental stress and algae cover. Motile animals showed functional dispersion along the biotic gradient, while sessile animals showed a functional trait shift along the stress gradient. This suggests that motile animals may respond through biotic facilitation, driven by the combined effects of decreased stress and increased algal cover. Lastly, predator-exclusion cages were deployed to investigate whether predators considerably affect community composition. The experiment used Indothais blanfordi, a predatory sea snail, as the focal predator of Brachidontes mussels. Indothais had a strong effect on both Brachidontes mussels and community composition. Together, the results show that the environmental stress gradient structured the community through environmental filtering. However, the mechanisms through which this occurs are nuanced and depend on organismal life histories, biotic interactions and fine-scale habitat mediators. These findings extend environmental stress gradients and environmental filtering theory, developed primarily along temperate shores, into an understudied tropical system. In doing so, it provides an ecological foundation and methodological framework from which further questions can now be pursued.
Ecology of the Great Indian Bustard (Ardeotis nigriceps) in Kachchh, Gujarat, with reference to resource selection in an agro-pastoral landscape.
(Wildlife Institute of India, Dehradun, 2013) Dutta, Sutirtha; Jhala, Y.V.; Rahmani, Asad R.
The Great Indian Bustard is an obligate grassland bird endemic to this region with a global population of only about 300 birds. Present study is based on Species's status, resource selection, behavioual aspects and socio-ecological context to reformate viable bustard conservation strategies. The study was conducted during 2007-11 in SW Kachchh (Gujarat, India)
HABITAT SELECTION BY DESERT FOX (Vulpes vulpes pusilla) IN HUMAN MODIFIED LANDSCAPE OF THAR DESERT
(Wildlife Institute of India, Dehradun, 2024) Krishnapriya, M.; Dutta, Sutirtha; Talukdar, Gautam
Knowledge about habitat use and selection helps to assess the impact of land use change on wildlife and inform conservation management. This study aims to understand habitat use and den site selection of Desert Fox (Vulpes vulpes pusilla) in the human modified landscape of Desert National Park and it adjoins in Rajasthan. The study was conducted from January 2024 to April 2024 that include the fox breeding season. Species occupancy inside and outside protected areas were examined to understand the effectiveness of protection. Den site selection was examined by comparing habitat, resource, and disturbance variables at the scale of core usage around the den and random control points. Protected area showed a positive effect on occupancy of foxes. Desert fox was found to be using diverse habitat types for denning, however, scrubland tended to be used more than availability and grassland was used less than availability, in the study area. Agriculture did not influence den site. Foxes showed strong avoidance to areas with high human and livestock disturbances and strong preference to areas with abundant Capparis fruiting for denning. Increase in human footprint in the landscape could potentially lower the survivability and reproductive success of foxes by making them prone to direct threats from humans and subsidized predators such as dogs.
Has conservation gone to the dogs? : ecological aspects of free ranging dogs of the Thar
(Wildlife Institute of India, Dehradun, 2017) Mohandas, Monisha S.; Jhala, Y.V.; Qureshi, Qamar; Dutta, Sutirtha
One of the few mammals to have a near-global distribution, dogs (Canis familiaris) are an introduced mammalian predator. Dogs have contributed to 11 vertebrate extinctions and are a potential threat to 188 threatened species globally. This study investigates population sizes, ranging patterns, behavioural activity, and resource utilisation of free-ranging dogs in Thar landscape, Rajasthan. 2. Using double sampling framework, I calibrated effort-standardized counts (C) with mark-recapture based abundances (𝑁̂) that was used to estimate dog abundances within human habitation. Landscape-scale dog abundance was estimated using vehicle transect based distance sampling. Home ranges of nine free-ranging dogs was determined using locations from radio-telemetry. Resource use was quantified as feeding durations on various food items based on continuous monitoring. Resource availability was quantified as wild prey and livestock carcass density using line transect based distance sampling. This study provides information on important aspects of free-ranging dog ecology and their impacts in Thar landscape. It provides the basis required for implementing dog control programs in the landscape focusing on the flagship and critically endangered great Indian Bustard Ardeotis nigriceps.
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.
Investigating the roles of fire and cattle grazing on vegetation, invasives, and their implications on Bengal Florican (Houbaropsis bengalensis) breeding habitat use
(Wildlife Institute of India, Dehradun, 2025) Thammaiah, Aadya; Nath, Anukul; Dutta, Sutirtha
Grasslands, though ecologically important, are often overlooked in conservation. These ecosystems are shaped by land-use practices such as fire and grazing, which can help maintain open habitats when appropriately applied. Mismanagement, however, can promote invasive species, threatening native biodiversity. The Bengal Florican (Houbaropsis bengalensis), a critically endangered grassland specialist, highlights the need for targeted conservation in such systems. This study assessed the combined effects of fire and grazing on grassland plant communities, including invasive plants, and Bengal Florican breeding habitat selection in Manas National Park. 2. For the vegetation survey, I selected study sites along gradients of fire frequency (based on 23 years of FIRMS data) and grazing intensity (using distance from human settlements as a proxy). At each site, I used circular plots to sample vegetation and assess species composition. To examine drivers of plant and invasive species abundance, I applied linear models (LMs), incorporating key covariates such as distance to forests, roads, and climate moisture index (CMI). I then used Indicator Species Analysis (ISA) to identify species associated with different fire-grazing regimes. I also performed a Linear Discriminant Analysis (LDA) to assess how well vegetation communities and structure could distinguish between different fire conditions. For Bengal Florican habitat assessment, I quantified vegetation structure visually and insect abundance using sweep netting in display and paired control sites. I used Binomial Generalised 8 Linear Models (GLMs) and Conditional Logistic Regression modelling to evaluate habitat selection by the species. 3. Tree and sapling densities peaked under intermediate fire, whereas shrubs and herbs had the highest density in low fire regimes. Saplings, shrub as well as grass cover peaked in low grazing regimes, but herb cover was highest in low grazing conditions. Among invasives, Leea asiatica and Chromolaena odorata were more frequent in intermediate fire, while Mikania micrantha and Ageratum conyzoides thrived under low fire. Grazing showed significant effects only on Mikania micrantha. ISA identified native species such as Dillenia pentagyna as indicators of low grazing and Cymbopogon flexuosus for medium and high fire regimes, among others. Bengal Florican selected sites with higher insect abundance, shorter vegetation (25–50 cm), with low (outside the PA) and high fire frequency (within the PA). 4. My results showed that plant communities showed species-specific responses to fire and grazing conditions. Bengal Florican habitat-use reflected a preference for open, short grasslands with high insect abundance. In conclusion, my study found that effective conservation requires tailored fire and grazing strategies that sustain open structure and control invasives, especially for the conservation of species such as the Bengal Florican.
Modernization at the cost of biodiversity and traditional livelihood in Kachchh
(Wildlife Institute of India, Dehradun, 2012) Dutta, Sutirtha; Bopanna, I.P.; Maurya, Kamlesh; Jhala, Y.V.
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.
Thermal Ecology of Spiny-tailed lizard and its vulnerability to climate warming.
(Wildlife Institute of India, Dehradun, 2021) Tatu, Avichal; Dutta, Sutirtha; Das, Abhijit
Lizards and other ectotherms survive within their thermal limits and have a well-defined range of body temperatures within which their performance is optimal. Hence, as climate warming accelerates, ectotherms like lizards become increasingly constrained. Saara hardwickii survives in areas where environmental temperatures are already extreme. Therefore, they may be at the risk of extinction due to rising temperatures. In the field, we collected data on field body temperatures and operative temperatures to evaluate and quantify the degree of thermoregulation observed in the lizard and to evaluate changes in activity pattern over months, In the laboratory, we quantified preferred temperature, thermal thresholds and locomotor of the lizard. Using a combination of field and laboratory data, we described how S. hardwickii uses burrows to thermoregulate and evaluated how climate warming will impact locomotor performance and hours of activity in the future. We found that burrows provide an exceptional buffer to the lizards as the temperatures deep inside (~1 m) do not exceed the preferred temperature of the lizard, even in the worst-case climate change scenario (RCP 8.5). Currently, the lizards are restricted to their burrows for six hours during their active period. According to our model, by 2100, the lizards might get restricted to their burrows for 7 hours in the best-case scenario, and for 9 hours in worst-case scenario. Our model suggested decrease in locomotor performance by 2.1%, 9.5% and 28.3% in the best- (RCP 2.6), intermediate- (RCP 4.5), and worst- (RCP 8.5) case scenarios by 2100. Hence, the synergistic effect of loss of activity hours and decline in locomotor performance might result in decreased fitness of S. hardwickii, potentially leading to its extirpation.