- Journal Article2013Antelope mating strategies facilitate invasion of grasslands by a woody weed.Oikos. 122(10): 1441-1452.Download
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Intra and interspecific variation in frugivore behaviour can have important consequences for seed dispersal outcomes. However, most information comes from among-species comparisons, and within-species variation is relatively poorly understood. We examined how large intraspecific differences in the behaviour of a native disperser, blackbuck antelope Antilope cervicapra, influence dispersal of a woody invasive, Prosopis juliflora, in a grassland ecosystem. Blackbuck disperse P. juliflora seeds through their dung. In lekking blackbuck populations, males defend clustered or dispersed mating territories. Territorial male movement is restricted, and within their territories males defecate on dung-piles. In contrast, mixed-sex herds range over large areas and do not create dung-piles. We expected territorial males to shape seed dispersal patterns, and seed deposition and seedling recruitment to be spatially localized. Territorial males had a disproportionately large influence on seed dispersal. Adult males removed twice as much fruit as females, and seed arrival was disproportionately high on territories. Also, because lek-territories are clustered, seed arrival was spatially highly concentrated. Seedling recruitment was also substantially higher on territories compared with random sites, indicating that the local concentration of seeds created by territorial males continued into high local recruitment of seedlings. Territorial male behaviour may, thus, result in a distinct spatial pattern of invasion of grasslands by the woody P. juliflora. An ex situ experiment showed no beneficial effect of dung and a negative effect of light on seed germination. We conclude that large intraspecific behavioural differences within frugivore populations can result in significant variation in their effectiveness as seed dispersers. Mating strategies in a disperser could shape seed dispersal, seedling recruitment and potentially plant distribution patterns. These mating strategies may aid in the spread of invasives, such as P. juliflora, which could, in turn, negatively influence the behaviour and ecology of native dispersers.
- Journal Article2013People, predators and perceptions: patterns of livestock depredation by snow leopards and wolves.Journal of Applied Ecology 50 (3), 550-560
- Journal Article2013Understanding the patchy distribution of four-horned antelope Tetracerus quadricornis in a tropical dry deciduous forest in Central IndiaJournal of Tropical Ecology, 1-10. doi:10.1017/S0266467413000722
At the landscape level, the four-horned antelope is confined to tropical dry deciduous forests and within these, their distribution is patchy. Various factors have been proposed as determinants for their patchy distribution within landscapes, but none provided an adequate explanation. We hypothesized that availability of a constant supply of forage influenced the species distribution.We found that the four-horned antelope mainly fed on fruits and flowers, and that a total of 60% of the tree species in Panna Tiger Reserve bore fruits at different times of the year. High tree species richness in habitat patches was considered a surrogate for constant supply of forage for the four-horned antelope. Data from 547 sighting locations between 2002 and 2006 and six spatial layers were analysed using maximum entropy to produce a probability distribution model for the four-horned antelope in Panna Tiger Reserve. Our model predicted that habitat patches summing up to only 9.5% of the 543 km2 of Panna Tiger Reserve had high probability of distribution (>0.5) of four-horned antelope. Although all variables contributed to the distribution model of the four-horned antelope, explanatory power was highest for tree species richness within habitat patches. The distribution of four-horned antelope within tropical dry deciduous forests can be treated as an indicator of high tree diversity and hence habitat quality.
- Journal Article2013Design and Evaluation of a Robust Optical Beam-Interruption-Based Vehicle Classiﬁer SystemIEEE Transactions on Intelligent Transportation Systems 14(3): 1043-1052Download
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This paper presents the design and development of a novel optical vehicle classifier system, which is based on interruption of laser beams, that is suitable for use in places with poor transportation infrastructure. The system can estimate the speed, axle count, wheelbase, tire diameter, and the lane of motion of a vehicle. The design of the system eliminates the need for careful optical alignment, whereas the proposed estimation strategies render the estimates insensitive to angular mounting errors and to unevenness of the road. Strategies to estimate vehicular parameters are described along with the optimization of the geometry of the system to minimize estimation errors due to quantization. The system is subsequently fabricated, and the proposed features of the system are experimentally demonstrated. The relative errors in the estimation of velocity and tire diameter are shown to be within 0.5% and to change by less than 17% for angular mounting errors up to 30°. In the field, the classifier demonstrates accuracy better than 97.5% and 94%, respectively, in the estimation of the wheelbase and lane of motion and can classify vehicles with an average accuracy of over 89.5%.
- Journal Article2013Green turtle herbivory dominates the fate of seagrass primary production in the Lakshadweep islands (Indian Ocean)Marine Ecology Progress Series. 485:235-243
Historical global declines of megaherbivores from marine ecosystems have hitherto contributed to an understanding of seagrass meadow production dominated by detrital path- ways — a paradigm increasingly being questioned by recent re-evaluations of the importance of herbivory. Recoveries in green turtle populations at some locations provide an ideal opportunity to examine effects of high megaherbivore densities on the fate of seagrass production. We conducted direct field measurements of aboveground herbivory and shoot elongation rates in 9 seagrass meadows across 3 atolls in the Lakshadweep Archipelago (India) representing a gradient of green turtle densities. Across all meadows, green turtles consumed an average of 60% of the total leaf growth. As expected, herbivory rates were positively related to turtle density and ranged from being almost absent in meadows with few turtles, to potentially overgrazed meadows (ca. 170% of leaf growth) where turtles were abundant. Turtle herbivory also substantially reduced shoot elongation rates. Simulated grazing through clipping experiments confirmed this trend: growth rates rapidly declined to almost half in clipped plots relative to control plots. At green turtle den- sities similar to historical estimates, herbivory not only dominated the fate of seagrass primary pro- duction but also drastically reduced production rates in grazed meadows. Intensive turtle grazing and associated movement could also modify rates of detrital cycling, leaf export and local carbon burial, with important consequences for the entire seascape.
- Journal Article2013Globalization of the Cashmere Market and the Decline of Large Mammals in Central AsiaConservation Biology 27, no. 4 (2013): 679-689
- Journal Article2013Influence of gaze and directness of approach on the escape responses of the Indian Rock Lizard, Psammophilus dorsalis (Gray, 1831).Journal of Biosciences. 38(5): 829–833.Download
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Animals often evaluate the degree of risk posed by a predator and respond accordingly. Since many predators orient their eyes towards prey while attacking, predator gaze and directness of approach could serve as conspicuous indicators of risk to prey. The ability to perceive these cues and discriminate between high and low predation risk should benefit prey species through both higher survival and decreased energy expenditure. We experimentally examined whether Indian rock lizards (Psammophilus dorsalis) can perceive these two indicators of predation risk by measuring the variation in their fleeing behaviour in response to type of gaze and approach by a human predator. Overall, we found that the gaze and approach of the predator influenced flight initiation distance, which also varied with attributes of the prey (i.e. size/sex and tail-raise behaviour). Flight initiation distance (FID) was 43% longer during direct approaches with direct gaze compared with tangential approaches with averted gaze. In further, exploratory, analyses, we found that FID was 23% shorter for adult male lizards than for female or young male (FYM) lizards. In addition, FYM lizards that showed a tail-raise display during approach had a 71% longer FID than those that did not. Our results suggest that multiple factors influence the decision to flee in animals. Further studies are needed to test the generality of these factors and to investigate the proximate mechanisms underlying flight decisions.
- Journal Article2013Role of Tibetan Buddhist Monasteries in Snow Leopard ConservationConservation Biology. DOI: 10.1111/cobi.12135
- Journal Article2013Globalization of the Cashmere Market and the Decline of Large Mammals in Central AsiaConservation Biology 27: 679-689
- Journal Article2013Large carnivores and low diversity of optimal prey: a comparison of the diets of snow leopards Panthera uncia and wolves Canis lupus in Sarychat-Ertash Reserve in KyrgyzstanOryx DOI:10.1017/S0030605313000306
- Journal Article2013Reversible immobilization of free-ranging snow leopards (Panthera uncia) using a combination of Medetomidine and Tiletamine-ZolazepamJournal of Wildlife Diseases DOI: 10.7589/2012-02-049
- Journal Article2012Structure and dynamics of South East Indian seagrass meadows across a sediment gradientAquatic Botany, 98 (1): 34-39Download
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In this study we examine the influence of non-monsoon sediment arrival on the high-diversity SE Indian seagrass meadows of the Palk Bay and the Gulf of Mannar. We used a gradient-based approach to examine the influence of increasing sediment loads on species composition and shoot density. In addition, for the ubiquitous seagrass (Cymodocea serrulata), we tested the influence of sediment on its biomass and productivity. We identified three sites in Palk Bay and four sites in Gulf of Mannar (SE India) along a gradient of sediment input. At each of the seven locations, sediment traps were deployed to measure sedimentation rates. Nine seagrass cores were taken systematically along 50 m transects at a constant sub-tidal depth to measure shoot density and biomass. A few shoots of C. serrulata were marked to estimate the above ground seagrass growth rate. Our results indicate that sedimentation rates that ranged from 8.6 to 62.4 mg DW cm−2 d−1 could not explain species composition of the meadow or shoot density of the observed species. C. serrulata was, by far, the most abundant species and present in all sediment condi- tions. Sedimentation rates did not alter shoot elongation rates in C. serrulata, ranging from 1.54 ± 0.29 SD to 0.25 ± 0.02 SD cm d−1 , but in contrast, increased vertical rhizome elongation rate. This increase was reflected in an increase in below ground biomass along the sediment gradient (R2 = 0.582, p = 0.01). C. serrulata appears to be able to adapt to the sediment dynamics in this area by allocating resources to rhizomes and roots to counteract burial and stabilizing sediments. Given that siltation is one of the most important threats to seagrass meadows, understanding the species-specific adaptive mechanisms of seagrass species in these high-sediment, high diversity South Asian meadows is an important first step in ensuring their long-term survival and functioning
- Journal Article2012Streamside amphibian communities in plantations and a rainforest fragment in the Anamalai hills, IndiaJournal of Threatened Taxa 4: 2849–2856.Download
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Stream amphibian communities, occupying a sensitive environment, are often useful indicators of effects of adjoining land uses. We compared abundance and community composition of anuran amphibians along streams in tea monoculture, shade coffee plantation, and a rainforest fragment in Old Valparai area of the Anamalai hills. Overall species density and rarefaction species richness was the highest in rainforest fragment and did not vary between the coffee and tea land uses. Densities of certain taxa, and consequently community composition, varied significantly among the land uses, being greater between rainforest fragment and tea monoculture with shade coffee being intermediate. Observed changes are probably related to streamside alteration due to land use, suggesting the need to retain shade tree cover and remnant riparian rainforest vegetation as buffers along streams.
- Journal Article2012Distance-related thresholds and influence of the 2004 tsunami on damage and recovery patterns of coral reefs in the Nicobar IslandsCurrent Science 102:1199–1205
The earthquake and tsunami of 2004 resulted in the devastation of marine and coastal ecosystems across the Indian Ocean. However, without adequate baseline information it has been difficult to properly gauge its full impact. The reefs of the Nicobar Islands in the Bay of Bengal lie on a path that ranges from 190 to 500 km from Banda Aceh, the epicentre of the 2004 tsunami. In 2008, we recorded benthic damage as a result of the tsunami to reefs off 14 Nicobar Islands across a gradient of distance from the epicentre. A clear pattern was observed in the demographic structure of the most abundant coral genera, Acropora and Porites across the distance gradient. Significantly, for the largest coral individuals of both genera (> 50 cm diameter), there were distinct threshold effects – their abundance declining dramatically in reefs closer than 350 km from the epicentre. Corals between 20 and 50 cm diameter also increased with distance from the epicentre, but in a more linear fashion. Smaller size classes either showed no apparent trend (Acropora) or decreased linearly (Porites) with distance. These gen- era represent very different life-history strategies: Acropora is fast-growing and highly susceptible to a range of disturbances, while Porites typically grows slowly but is resistant to disturbance. The fact that both genera showed similar thresholds indicates that, close to the epicentre, the impact of the earthquake and tsunami was large enough to override any species- specific resistance. Also, algal cover was also much higher than at locations further north, linked to higher coral mortality at these locations. However, the fact that smaller size class coral individuals were rela- tively abundant and even increased close to the ep centre indicates possible paths of reef recovery after the catastrophe.
- Journal Article2012Averting biodiversity collapse in tropical forest protected areas.Nature 489: 290-294.
- Journal Article2012Standardizing the double-observer survey method for estimating mountain ungulate prey of the endangered snow leopardOecologia DOI: 10.1007/s00442-011-2237-0
- Journal Article2012Impact of vehicular traffic on large mammal use of highway-edges in southern IndiaCurrent Science 102(7): 1047-1051Download
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India’s phenomenal economic growth over the last decade has been accompanied by a much-needed expansion and improvement in transport and other infrastructure networks. While there are legally mandated assessments of the potential ecological impacts of such infrastructure projects prior to implementation, rarely are there post-implementation assessments of their real ecological impacts. In this communication, we present results of a preliminary study examining the impact of vehicular traffic on the usage of road edges by large mammals along a highway passing through Nagarahole Tiger Reserve, southern India. We estimated large mammal encounter rates at remotely triggered camera traps on two consecutive sections of the same highway – one closed to vehicular traffic and the other open to vehicles only during daytime. We observed lower encounter rates of chital, gaur and elephants at camera traps in the highway segment with higher vehicular traffic density, suggesting that these species avoided busy highways. Based on our findings, we emphasize the importance of continued ecological impact assessments of development projects to identify and mitigate unforeseen impacts. Further, an approach to development planning that integrates conservation concerns, especially where development projects coincide with ecologically critical areas, is urgently needed in India.
- Journal Article2012Socio-economic drivers of Forest Cover Change in Assam: A Historical PerspectiveEconomic and Political Weekly 47(5): 64-72Download
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This article analyses the historical context of forest cover change in the upper Brahmaputra Valley of Assam during the precolonial, colonial and the postcolonial periods, locating these changes within the political economy and demographic milieu of each regime.In the current context of rising populations linked to immigration from neighbouring regions, dwindling share of agriculture in the state’s gross domestic product, and recent incentives to small tea growers in risk-prone agricultural landscapes, serious challenges remain to securing forests in this region. Empowering local communities and institutions, understanding tea plantation dynamics and managing the causes and consequences of recent demographic change are crucial to the conservation of forests there.
- Journal Article2012Optimizing individual identification and survey effort for photographic capture–recapture sampling of species with temporally variable morphological traitsAnimal Conservation 15(2): 174-183
Endangered, wide-ranging megafauna have many threats to contend with during their struggle for survival in an ever-increasing human dominance of the environment. Reliable monitoring of endangered large mammal populations is therefore a critical conservation requirement. Photographic capture–recapture (CR) techniques have opened up avenues for population monitoring of individually recognizable large mammal species. The efficient application of these techniques, however, can be constrained by challenges in reliably identifying individuals arising from the use of multiple, and potentially variable traits, as well as issues of temporal sampling of populations in the field. We address these key problems by describing an automated process of rapidly identifying individual Asian elephants (Elephas maximus) from photographs, and comparing resultant CR-based population parameter estimates with those obtained using supervised visual identification of individuals. In addition, we assess the temporal effort necessary for robust estimation of demographic parameters in our study population. Morphological traits that maintain constancy over time, including variations in tusk characteristics, and ear fold and lobe shape, proved the most reliable for individual identification and subsequent estimation of population parameters. The use of temporally variable traits contributed to high probabilities of misidentification and biased estimates of population size. We found a minimum of seven sampling occasions necessary for reliable population estimation. Our study contributes to design issues for CR studies by providing insights into optimality of sampling effort such that precision of parameter estimates are not compromised while minimizing survey costs. We demonstrate the importance of accurate individual identification in the context of such studies and recommend the use of fixed morphological traits as the optimal individual identification strategy for species where animals are distinguished on the basis of multiple attributes, including some that may be variable over time.
- Journal Article2012Conservation needs of the Coconut Crab (Birgus latro) on the Nicobar Islands, IndiaOryx, 46: 175-178.Download
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We describe the distribution of the coconut crab Birgus latro, categorized as Data Deficient on the IUCN Red List, local perspectives towards the species, and its conservation needs on the Nicobar Islands in the eastern Indian Ocean. The species is threatened with extinction across most of its range and in India it is found only on a few islands in the Andaman and Nicobar archipelagoes. We carried out informal discussions with Nicobari commu- nities to examine issues regarding conservation of the species and conducted timed searches in areas where coconut crabs were likely to be found. The discussions revealed that there are social taboos against hunting the coconut crab on most of the Nicobar Islands. However, on some islands these taboos are not being followed and community members may hunt the crab for consumption. Athough the coconut crab is legally protected under the Indian Wildlife Protection Act none of the villagers were aware of this. Of the six islands surveyed we recorded the presence of 17 and 14 crabs on two islands, respectively. On four islands villagers reported the presence of the crab prior to the tsunami of 2004, and on two of these islands the species may now be locally extinct. A small population size and a fragmented distribution in areas of coconut planta- tions suggest that the species is threatened. We recommend monitoring and detailed research on the ecology and genetics of the coconut crab, along with community-based conservation initiatives to conserve the species and its habitat.