Theses and Dissertations

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Author: search.filters.author.Jhala, Y.V.Subject: search.filters.subject.Population density

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    Spatial abundance of ungulates and role of predation on chital (Axis axis) demography and behaviour in Corbett Tiger Reserve, Uttarakhand, India.
    (Wildlife Institute of India, Dehradun, 2022) Banerjee, Sudip; Jhala, Y.V.; Qureshi, Qamar
    To address the first objective which was to estimate the abundance of ungulates in different habitats of CTR, I have used line transect-based distance sampling approach to estimate the density of four major ungulate species (chital, sambar deer, barking deer, and wild pig) of CTR in ~520 sq. km of the Corbett National Park (CNP) region. Density was estimated using 156 spatial transects replicated 1 to 4 times over four sampling years. Both year-wise and pooled (weighted average of four years) density estimates were highest for chital followed by sambar. Barking deer had the lowest density. Chital density has remained stable over the years. Post-stratifying the densities of the four ungulates by three major habitat types of CNP (grassland, saldominated, and mixed deciduous) exhibited the highest density of chital in the grassland and lowest in the sal-dominated forest. Sambar density on the other hand was highest in the mixed deciduous and lowest in the grassland. Barking deer also exhibited a similar trend of habitat-wise density. A significant part of my thesis was focused on the objective of evaluating the precision and cost-effectiveness of three different density estimation techniques. The diverse ungulate assemblage and complex terrain of CNP provided an excellent environment to conduct this experiment.
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    Occupancy and abundance of tigers and their prey in Terai Arc Landscape, Nepal.
    (Wildlife Institute of India, Dehradun, 2012) Karki, Jhamak Badur; Jhala, Y.V.; Pandav, Bivash
    The occupancy, distribution and tiger density are important information for management and conservation policy formulation. Realizing this need, this study was undertaken. The major wild prey species of tiger are spotted deer (Axis axis), wild pig (Sus scrofa), sambar (Rucervus unicolor), swamp deer (Rucervus duvaucelli duvaucelli), barking deer (Muntiacus muntjak), hog deer (Heylaphus porcinus) and gaur (Bos gaurus) in Nepal. To evaluate the occupancy of tiger in Nepal's Terai Arc landscape (TAL), sign survey was conducted in 96 grids (area 225 Km2 ) in 14 districts, including PAs. To assess correlation of the tiger occupancy with the availability of wild prey, and the human disturbance with the habitat use by the tiger, the sign of human disturbances (fire, timber cut, fuel wood collection, sign of poaching) and prey presence were recorded during the winter season. To estimate the density of tigers wild prey in PAs of Nepal's TAL, distance sampling was conducted along the predefined line transects during the summer season
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    Abundance, Habitat Relationships and Behavior of the Semi-Fossorial Indian Desert Jird, Meriones hurriancae, in Kachchh, Gujarat
    (Wildlife Institute of India, Dehradun, 2011) Ramesh, Divya; Jhala, Y.V.; Qureshi, Qamar
    Population sizes, habitat relationships and behaviour are among basic ecological aspects pivotal to demystifying a species and its place in the ecosystem. Numerous in species and number, desert rodents offer immense scope for such investigations. The Indian desert jird, Meriones hurrianae, though common, is remarkably little known. This study, conducted in Kachchh, Gujarat, estimates population sizes, examines factors in the habitat likely to influence their occurrence, and elucidates the activity pattern and time budget across 2 land use types, agricultural and natural areas, during winter (December February) and summer (March-May). Animals were caught in 9 colonies using Sherman traps and population estimated under closed population Capture-Mark-Recapture framework in Program MARK, using individual covariates (age class, gender, body weight, site). Colony parameters (length, width, number of holes) were regressed against known Mark-Recapture (MR) population estimates to develop predictive models for estimating population size from indices. Population sizes varied from 2 to 10 individuals. Number of holes in a colony provided robust estimates of the number of individuals in that colony (N=16, R2=0.96, t=18.19, p
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    Evaluating Tiger (Panthera tigris) Population Estimation Approches in a High Density Area in Kanha Tiger Reserve
    (Wildlife Institute of India, Dehradun, 2005) Sharma, Rishi Kumar; Jhala, Y.V.
    Reliable estimates of status and population trends are critical for the conservation of large terrestrial carnivores as they play an important role in evaluating effectiveness of conservation efforts and also provide benchmark data for future management decisions. Camera trapping technique have been widely used for population estimation of cryptic carnivores including tigers, but the issues regarding sampling design and effort required to effectively sample an area have been paid less attention. An attempt was made to deal with these issues in the present study. The use of intensive search effort for tiger density estimation was also evaluated. Over a 30- day survey period, 33 camera trap sites were sampled in Kanha meadows of the Kanha Tiger Reserve. A total sampling effort of 330 trap nights yielded 39 photocaptures of 12 individual tigers over 10 sampling occasions that effectively covered a 111-km2 area. The model M(o) fitted the capture history data well. The estimated capture probability/sample, p-hat = 0.22, resulted in an estimated population size and standard error (N(SE TV)) of 13 (1.19), and a density (D(SE Z))) of 11.71 (1.74)7100 km2. Camera spacing was found to considerably influence the population estimation. An increase in camera spacing from 1.5 to 2.5 km resulted in a loss of 35% (n=7) of photo captures which consequently decreased the precision of the estimates, though accuracy was not affected. A reduction in the trapping effort in terms of reduced trap nights resulted in lower level of precision though the accuracy of estimates was not affected. Increase in the camera spacing from 1 to 2 km with a decrease in the number of sampling occasions (six) resulted in the loss of 42% of photo captures (n=12) and loss of 25% of individual tigers (Mz+/=9) thus underestimating the true tiger population by 16% ((N(SE N)) being 10(1.84) The data also suggests that the photo-captures are not likely to generate abundance index for species other than tigers, since the cameras are placed to maximize tiger captures in space and time. My results suggest that a thorough reconnaissance survey is of utmost importance for camera trapping studies as it can help to maximize the capture probability of tigers and circumvent the sampling problems. The different statistical estimator’s viz. capture-recapture, jackknife and bootstrap did not show significant differences in the population estimation. Bootstrap estimator performed better than jackknife in terms of greater precision. The differences between the density estimates generated by “camera trapping” (D=l 1.71/100 km2, S.E.=1.74) and “intensive search effort” (0=12.74/100 km2, S.E.=2.27) for tigers were not significantly different. Our results suggest that “intensive search effort” for tigers if used within capture-recapture framework can be used to arrive at reliable population estimation