Theses and Dissertations

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    Assessing Ghost crab distribution, abundance and habitat use along the Coromandel Coast, Tamil Nadu
    (Wildlife Institute of India, Dehradun, 2025) Keerthi V; Gopi, G.V.
    Sandy beach ecosystems around the world are facing numerous threats and tremendous pressure due to ever increasing human population. One such threat, relevant to the Indian coastline, is the large scale plantations of shelterbelts of the exotic pine, Casuarina equisetifolia, which alters beach geomorphology. The effects of such plantations on permanent shore-dwelling organisms are poorly studied. Hence Ocypode crabs, the most conspicuous macro-invertebrate on sandy beaches, has been used as a model taxon to study the effects of different kinds of inland vegetation (Casuarina plantations, Mangrove plantations, native dune vegetation) on beach geomorphology and consequently, shore dwelling ghost crabs. The present study aims to - (1) Assess the density, distribution and demography of ghost crabs across treatments (2) Understand variations in habitat use and burrow architecture across treatments (3) Understand the effects of inland vegetation on beach geomorphology 2. A total of 24 transects, temporally replicated thrice each month between January 2025 - April 2025, were walked to estimate densities of ghost crabs using burrow counts as a proxy. 87 burrows across the treatments were cast using a mixture of Plaster of Paris and water and traits such as depth, diameter, shape and branching patterns were studied. Coast characteristics like slope, compactness, beach width, moisture and temperature were recorded at each study site. 3. Mean burrow densities and across shore distribution of Ocypode ceratophthalmus differed across the treatment types, with lowest densities in beaches adjacent to Casuarina plantations. This however wasn't statistically significant. The burrow structures also differed in complexity across treatments with the major drivers for this 7 difference being the size of the crab and the type of inland vegetation. Environmental variables were not found to have significant effects on burrow architecture. 4. The results indicate that the type of inland vegetation affects the population of ghost crabs through changes in beach geomorphology. Ghost crabs were also found to modify the structure of their burrows with changes in the habitat quality and environmental conditions, which gives insights into their adaptive capacities. The study, thus raises questions on the effects of certain management interventions, like the planting of shelterbelts on habitat quality and on the ecology of the species dwelling in the said habitats.
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    Pollinator Visitation and Reproductive Success in Two Species of Mangrove Plants, in Bhitarkanika Wildlife Sanctuary, Orissa
    (Wildlife Institute of India, Dehradun, 1997) Pandit, Shalini; Choudhury, B.C.
    Visitation patterns to the flowers of Sonneratia caseolaris and Aegiceras corniculatum were investigated between December 1996 and April 1997, in the mangrove forests of Bhitarkanika Wildlife Sanctuary, Orissa. The objectives of the study were to determine the pollination effectiveness of the different categories of visitors by quantifying their rate of visitation. The effect of environmental variables on visitation was examined, and the importance of the visitors to the reproductive success of the plant was investigated by conducting exclusion experiments (Le. bagging flowers to prevent visitation). Nectar was analysed for volume and sucrose content in S. caseolaris, and the impact of predation on the reproductive success of the plant was examined. The results of the study indicated that the flowers of both plant species attracted a wide array of visitors and did not show a specialised relationship with anyone visitor species/category. Different categories of visitors were seen to vary in their pollination effectiveness for the two plant species. Environmental variables such as temperature, sun intensity and wind velocity were seen to influence the visitation of Lepidoptera to the greatest extent, and Hymenoptera to a lesser extent. Visitation by birds was found to be independent of the environmental variables. The territorial behaviour of purple-rumped sunbirds at the S. caseolaris site was seen to reduce visitation of other birds and of bees to the flowers of this species. Results of the bagging set-ups indicated that there was no difference in the pollinator effectiveness of the nocturnal and diurnal visitors. Reproductive success was not pollinator-limited in either of the two plant species.