IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Karanth, K.U.; Nichols, J.D. | |
| Ecological status and conservation of tigers in India | |
| 2000 Full Book | |
Tiger (_Panthera tigris_) has been an important flagship species for biodiversity and wildlife conservation in India over the past thirty years. However, tigers are still considered highly endangered and have been targeted for a major recovery effort by the Indian government and conservation agencies. It is now recognized that such recovery efforts are seriously handicapped by a lack of baseline ecological information on tigers and their prey species. Consequently, the urgent need to develop suitable methods to gather baseline data and to monitor the recovery efforts is being increasingly recognized. We carried out this study to address a critical conservation need for developing rigorous methods to monitor tiger and prey populations and to obtain benchmark estimates of their densities under conditions that prevail in Indian Reserves. We investigated the use of two current animal population-sampling approaches to estimate the abundances of tigers and their principal prey species in nine ecologically representative nature reserves in India, between the years 1995-2000. Tigers were photographed using self-activated camera traps to obtain pictures from which individuals were identified using differences in stripe patterns. We analyzed the 'capture history' data from such identified individuals in a framework of formal capture-recapture sampling, using appropriate stochastic models to estimate capture probabilities and to derive estimates of tiger densities. We also carried out Line transect sample surveys on foot or fromelephant-back, in seven of these sites to estimate densities of the tiger's principal prey species. We found that generally camera-trapping protocols worked satisfactorily at densities higher than 3 tigers/ 100 km2, enabling the use of relatively more sophisticated and robust capture-recapture models that incorporate heterogeneous capture probabilities among different individual tigers. However, even at lower tiger densities, we found the capture-recapture sampling approach to camera-trapping to be superior to ad hoc camera-trapping methods. The line transect surveys of prey species generated reasonable estimates based on stochastic distance sampling models. Therefore, we recommend the application of the above two approaches for monitoring tiger and prey populations in high-density, priority conservation areas. The estimated densities of tigers over one year of age (expressed in number of tigers/100 km2) at different sites we surveyed were as follows: Pench = 4.9; Kanha = 11.7; Kaziranga = 16.8; Nagarahole = 11.9; Bhadra = 3.42; Bandipur = 11.97; Ranthambore = 8.2; and Sundarbans = 0.84. The tiger densities in Namdapha were too low to permit effective camera-trapping. The estimated combined densities (numbers/km2) of large ungulate prey at the above sites were, respectively: 63.8; 57.3; 58.1; 56.1; 16.8; 35.2 and 60.6. However, due to logistical and other constraints, we could only derive indices of prey abundance based on dung counts in Namdapha and could not derive any estimates of prey abundance in Sundarbans. The project has already generated one publication in the journal Ecology from its early results. We propose to publish several more scientific papers/monographs based either fully or partially on the results of this study. In addition, we are currently in the process of editing a technical manual for estimating and monitoring the abundance of tigers and prey species. Another technical product from this project consists of the design and development of an innovative protective shell to guard camera traps against theft and damage. This project also met its ancillary goals of local professional development and capacity building reasonably well. One project Research assistant went on to enroll in a Doctoral Program, two assistants completed their Master's degrees and three more are currently enrolled in Masters degree programs. Four more former assistants are currently pursuing careers in wildlife conservation. Additionally, 120 volunteer assistants who participated in the project field activities were trained in animal population survey methods and given certificates of proficiency. However, the goal of the project to train wildlife personnel managing the study areas could not be fully achieved due to a lack of adequate response at some sites. As a follow-up to this project, we also organized a higher-level technical workshop in association with Project Tiger for Indian and international participants to increase their exposure to the current sampling-based population estimation methods used in this study. The conservation implications of this study suggest that tigers in prime habitats in India can attain high densities of 10-20 animals/100 km2, figures much higher than those estimated based on radio telemetry studies earlier in Nepal and elsewhere. Furthermore, these optimal tiger densities in prime protected areas of India are 10-20 times higher than those reported in poor habitats. The related demographic modeling work done by the principal investigator suggests that even small reserves in India can maintain demographically viable populations of tigers, if they are adequately managed to maintain high prey densities. Based on this study, we make several specific management recommendations concerning the monitoring of tiger populations in India at different spatial scales and levels of manpower and resources availability. These recommendations include: geo-referenced mapping of tiger distribution on a country wide scale; application of sampling-based abundance indices based on signs of tigers and their prey in most reserves; establishment of potential carrying capacities for tigers using line transect surveys of principal prey in critically important reserves; and, monitoring absolute abundance of tigers using the camera-trap capture-recapture sampling at high-priority sites where adequate resources and skills are available. |
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