M Sc Dissertation(WII)
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Item Evaluating the importance of scale in estimating tiger populations(Wildlife Institute of India, Dehradun, 2007) Contractor, Deep; Jhala, Y.V.; Qureshi, QamarPopulation estimation is one of the most important aspects of ecological studies as it plays a pivotal role in establishing priorities for species specific conservation and for delineating management practices. The tiger serves as a flagship and umbrella species for conservation efforts in the Indian subcontinent but, unfortunately wild tiger populations are on a drastic decline owing to factors like poaching, habitat fragmentation and degradation. In such a scenario reliable population estimates prove to be of vital importance. Camera trapping technique has been widely used for population estimation of cryptic carnivores including tigers. An attempt was made, through this study, to arrive at population and density estimates for Corbett NP through camera trapping technique following the mark recapture framework and answering some key questions regarding the importance of sampling effort required for arriving at such reliable estimates. A total of 7865 trap nights yielded 358 captures of 103 individual tigers within an intensively sampled area of (MCP) 420.86 km2. The estimated density of tiger was 16.01 (±1.6) per 100 km2 for RPSV, a new approach to calculate effectively sampled area. These estimates coincided with the estimates using full MMDM method. Also, the conventional method of using half MMDM seems to overestimate the density. The estimated sampling effort required for arriving at accurate and precise estimates of the true population in terms of sampling occasions amounted to 35 - 40 days. Evaluation of the influence of trap density revealed that high trap density (25 traps/km2 ca.) is required to get reliable estimates of population irrespective of the underlying population/density gradient.Item 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 estimationItem Aspects of Foraging, Activity, Habitat Use and Demography of Rhinoceros (Rhinoceros unicornis Linn.) in Royal Chitwan National Park, Nepal(Wildlife Institute of India, Dehradun, 2003) Kandel, Ram Chandra; Jhala, Y.V.The study was conducted between November 2002 to June 2003 in the Royal Chitwan National Park, in Central Terai which arbors the largest population of the Great One-honed Rhinoceros (Rhinoceros unicornis Linn) in Nepal. I studied time Activity budget, Habitat use, preference, food habits and ranging pattern of free ranging rhinos by continuously monitoring them from elephant back for 130.5 hrs (10 sessions of 7-24 hr each)Item Home Range, Ranging Patterns and Abundance Estimation of Golden Jackals in the BHAL Region of Gujarat(Wildlife Institute of India, Dehradun, 2001) Aiyadurai, Ambika; Jhala, Y.V.Studied Golden Jackals (Canis aureus) in the Bhal area of Gujarat using radiotelemetry. Six jackals were trapped in Velavadar.National Park during November and December 2000 using rubber-padded leg-hald traps. The average home range size of jackals was estimated to be 14. 30 ± 4.06 sq. km. The core areas of jackal home ranges were highly correlated with vegetation cover. Habitats preferred for core areas were Prosopis juliflora and grasslands. Jackals ranged an average distance of 6.8 ± 0.91 km in a night. Most movements were out of the park to surrounding villages, which were rich in food resources for jackals. I evaluated two techniques to estimate jackal abundance namely the track plot method and simulated howling responses method in six areas differing in jackal abundances in the Bhal and Kutch regions. The latter technique gave a better resolution of abundance categories within the study sites.Item Evaluation of Pugmark Census Technique(Wildlife Institute of India, Dehradun, 2001) Sharma, Sandeep; Jhala, Y.V.Effective conservation strategies hinge on reliable population estimation technique. The potential of pugmark as a tool for population estimation of tigers was statistically examined. Eleven variables were selected and they were found effective in discrimination between individual tigers. These variables also discriminated between male & female in a population of 10 known tigers with 100% accuracy. This sex discrimination modal was found 97.4% accurate during validation over three new known tigers. The above said variables were also robust for pooling left and right pugmark. The soil depth of range 0.5 cm to 2 cm was found to be ideal for PI P preparation, since the 11 predictor variables were examined to be insensitive towards shape and size change of pugmark due to substrate condition. Classification of 17 individual tigers was achieved with 97% accuracy using stepwise discriminant function analysis. The statistical protocol developed in this study was found to be 100% accurate in predicting the correct number of tigers and correct classification of pugmarks, during validation in a blind set simulated 'census-exercise' from a known number of tigers (some of the track sets used for this analysis were not used for developing the DFA model). Variability in pugmark tracings due to tracer's effect was found to be significant. ANOVA (p-value 0.002 with df-1, df-53) results suggest a significant difference between variables measured from tracings and those from photos. However, DFA was unable to discriminate between tracings and photographs suggesting that either could be used in the model. Seventy five percent of the "experts" (n=8) were 100% correct in deciphering individual tigers in a blind test involving 15 tiger pugmarks from 7 individual tigers. The remaining 2 experts overestimated the tiger numbers by 1. The experts had an accuracy of 92% (sd = 7.8) in correct classification of tiger pugmarks. The other groups of respondents, ecologists (n=11) and lay persons (n=15) overestimated the tiger numbers and had an accuracy rate of 670/0 (sd = 24), and 640/0 (sd = 6) respectively in classifying pugmarks correctly. This study suggests that pugmarks can be used as a tool for population estimation of tigers, if subjected to analytical protocol developed here in within the constraints outlined.