Theses and Dissertations
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Item Evaluating the Impact of Introduced Spotted Deer (Axis axis) on Forest Floor Herpetofauna of Andaman Islands(Wildlife Institute of India, Dehradun, 2013) Mohnty, Nitya Prakash; Vasudevan, K.; Sivakumar, K.It is common knowledge that organism in an ecosystem, are connected to each other through trophic levels. Even though the importance of interactions among trophic levels is well established in theory, demonstration of such interactions is not always easy. Over the years, studies that focus on the trophic interactions among starkly different taxonomic groups have come to the fore. These studies have furthered our understanding of ecosystems by demonstrating relationships between trophic levels so apart, the connection among which may not be apparent at first. Along these lines, the situation of introduced spotted deer in the Andaman Islands presented an ideal opportunity to understand the potential effect of a mammalian invasive herbivore on native, insectivorous forest floor herpetofauna. I hypothesised that herbivory is likely to depress folivorous arthropod abundance, which in turn may lead to a decline of insectivorous forest floor herpetofauna. Additionally, reduction in vegetation cover may render the habitat unsuitable for herpetofauna and make them vulnerable to predation. The objectives of this study were to evaluate the effect of chital on the forest floor herpetofaunal abundance and to determine the pathway of interaction between them. A contrasting effect of herbivory by chital on reptiles and on amphibians in the Andaman Islands was observed during the dry season. Forest floor reptiles, which included agamids, geckos and skinks showed reduced abundance in the presence of chital in comparison to an island where chital was absent. This effect of chital on reptiles was found to be mediated by vegetation cover. Chital significantly reduced the vegetation cover below their maximum browse height (1.5 m) in the Islands and which in turn led to a reduction in reptile abundance. Although, it was not clear if any of the observed species was benefitted in the presence of chital, the semi-arboreal Coryphophylax subcristatus appeared to be affected. Amphibian abundance on the other hand seemed to be unaffected by the use of the habitat by chital. Litter arthropods influenced the densities of amphibians the most. This study brought to light a pathway of indirect interaction between a mammalian herbivore and insectivorous herpetofauna. In doing so it raised conservation concern about the capability of an introduced species to alter an island ecosystem drastically and acutely impact several endemic fauna.Item Computing Biomass Consumption from Prey Occurrences in Scats of Tropical Felids(Wildlife Institute of India, Dehradun, 2013) Chakrabarti, Stotra; Jhala, Y.V.; Qureshi, QamarA robust understanding of prey use and selection by carnivores provides crucial insights into their ecology, conservation and management. In majority of the cases, scat analysis is most effective to assess diet spectrum of carnivores, but require correction for potential biases for estimating biomass contribution of different prey items. Since small prey have higher indigestible matter per unit body mas~ due to higher surface area-to-volume ratio, relative frequencies of prey remains in scats do not represent their consumed biomasses. Thus ~ to accurately estimate the proportions of different prey consumed, it is necessary to develop relationships between biomass consumed per field collectable scat and prey weight through feeding experiments. However, no such relationship exists for felids of the Indian sub-continent. The studies on diet of big cats like lion (Panthera leo), tiger (Panthera tigris) and leopard (Panthera pardus) have used a similar relationship based on cougars (Puma concolor) by Ackerman et al. 1984 owing to the unavailability of any species specific relations. Methods: A series of feeding trials were used on Asiatic lion (Panthera leo persica), leopard and jungle cat (Felis chaus) to develop prey incidence to biomass conversion equations (hereafter mentioned as biomass models or biomass equations). Principal findings: All the models showed satiating relationships between biomass consumed per collectable scat and prey weight given by asymptotic exponential functions. However, carnivore specific models when scaled to their respective body weights did not differ significantly between each other, allowing derivation of a generalized biomass model for tropical felids. Inferences using present study models refined existing representation of diet of tropical carnivores. Significance: Results from the present study have strong implications on feeding ecology of tropical felids. Present study refined previous understanding of biomass contribution of different prey species in large felid diet by substantially increasing roportion of medium prey consumption. Such inferences question niche separation of sympatric large felids on the basis of prey species of different sizes, where large carnivores like tiger optimizing on large prey like gaur (Bos gaurus) and sambar (Rusa unicolor). while medium felids like leopard maximizing on chital (Axis axis). Domestic livestock significantly reduced in carnivore diet, reducing livestock depredation rates. indicating lower human-carnivore conflict levels.Item A Study of Vigilance Behaviour of Chital (Axis axis) in Pench Tiger Reserve, Madhya Pradesh(Wildlife Institute of India, Dehradun, 2009) Ghuman, Sartaj S.; Sankar, K.Predation is an important agent of natural selection in animal communities and so vigilance behaviour has very high selection pressure acting upon it. During feeding bouts, unless plant density and biomass are high and food intake is limited only by the processing rates, herbivores tend to experience a trade-off between vigilance and feeding. Thus, vigilance as a behaviour pattern ought to be tightly regulated by the cost-benefit ratios. A study on vigilance behaviour of chital (Axis axis) was conducted at Pench Tiger Reserve, Madhya Pradesh from December 2008 to April 2009. The objectives of the study were to examine the determinants of individual and group vigilance in chital; and also to examine the t effect of conspecific behaviour on individual vigilance. I used scan sampling with fixed interval recording to estimate group vigilance and focal animal sampling with continuous recording to estimate individual vigilance levels. Three main factors that are known to affect :, vigilance from studies on other herbivores were examined: group size, density of animals in the group and visibility. Scanning behaviour was used as an estimate of vigilance. 'Scanning' refers to the state when the animal has its head above shoulder level and the senses of sight, smell and hearing are actively 'scanning' the environment. Individual vigilance was found to decrease with increasing group size, decreasing density and increasing visibility. In large groups adult males, fawns and adult females with fawns were found to be significantly more vigilant than females without fawns and yearling males. Group vigilance level was found to increase significantly with increasing group size, even as the group scan level decreased. Individuals seemed to reduce vigilance with relation to group size rather than the group vigilance level. The results suggest that individual chital do not adopt levels of scanning that maximize cooperative predator detection. The benefits of the group size effect vary with age-sex classes and other probable internal and external predation risk Factors and so vigilance is more likely governed by a combination of dilution and detection hypotheses mechanisms, the focus changing from one to the other with individual risk.