A major challenge in conserving our national biological resources is the lack of scientific understanding of how meta-populations (spatially separated sub-populations linked to each other through occasional dispersal) of endangered, wide-ranging and elusive species of mammals function at macro-ecological scales (i.e. at large spatial and temporal scales). Furthermore, the functioning of meta-populations of apex predators such as the tiger (Panthera tigris) is closely linked to the dynamics of their prey species (in this case seven herbivore species) and syntopic predators (two species: leopard, P. pardus and dhole, Cuonal pinus). The primary goal of the project “Meta-population dynamics of tigers in the Malenad-Mysore Landscape of Karnataka” was to scale up insights gained from earlier site-level research in reserves to understand the meta-population dynamics of tigers, co-predators and prey across the 38,000 km2 Malenad-Mysore Tiger Landscape in Karnataka. Another important goal of the project was the development of appropriate field survey designs, population models and other technical tools needed to address these study questions.
Under the project, the Centre for Wildlife Studies (CWS) carried out intensive annual monitoring of tigers across 6 protected areas within the MMT Landscape. These intensive monitoring sites covered 6,000 km2 in area. Each year the monitoring team carried out camera trap surveys across 713 camera trap locations, investing over 23,000 trap-days of effort, to monitor tiger and leopard populations within a spatial capture-recapture framework. They also carried out line transect surveys using over 230 permanently-marked line transect samplers (each 3.2 km-long), investing approximately 5,700 km of walk effort annually to estimate densities of principal prey species of tigers.
They also carried out habitat occupancy surveys to assess the distribution of tigers across the entire MMT Landscape, and to understand the role of ecological and anthropogenic factors in determining where tigers occur. The first surveys were carried out in 2006-2007 (i.e. prior to the project period) and during the project the team carried out the second landscape-wide tiger occupancy surveys in 2014-2015. They invested over 5,000 km of survey effort in surveying for tiger detections across 208 grid cells (each 188-km2 in size), which yielded 564 detections of tiger presence across the landscape.
CWS also carried out surveys to collect tiger scat samples according to strict field protocols. Scat samples were also collected opportunistically by CWS field teams during other fieldwork, and these samples were sent to the National Centre for Biological Sciences (NCBS) for subsequent DNA extraction, genotyping and analysis. The analyses of the tiger genetic data from across the MMTL revealed a north-south gradient in genotypes, with Kali and Bhadra Tiger Reserves being quite distinct from BRT. Further analysis of the data show that there seems to be greater connectivity among tigers in the MMTL relative to those in central India. Using genetic markers known as single nucleotide polymorphisms (SNPs), NCBS scientists also assessed connectivity between tigers in the MMTL and other regions, finding that tigers across India segregate genetically into four distinct clusters, with southern India being separated from central, north and north-eastern India.
The intensive field monitoring has continuously informed the management of tiger populations across the MMTL, in several ways. The long-term monitoring shows that tiger and prey populations occur at high densities at Nagarahole, Bandipur and BRT but are nonetheless subject to high temporal fluctuations that are a natural feature of populations, due to demographic and environmental stochasticity. In Bhadra, prey and, recently, tiger populations are showing clear signs of recovery following conservation interventions catalyzed and facilitated by CWS over a decade ago. In other sites subject to human pressures (Kali, Cauvery-MM Hills, Kudremukh), tigers and prey continue to be suppressed at low densities. Such understanding of local population dynamics and the context in which conservation needs to be carried out is vital to determining the optimal management actions, which need to be tailored very differently for these different conservation and ecological contexts. The long-term monitoring has also recorded medium to long-range dispersal events by individual tigers and leopards, which has shed new insight into the movement of individuals and actual functional connectivity across sites within the MMTL. The study team continues to provide real-time inputs to park managers in the event of big cat poaching and other mortality, based on rapid, automated pattern matching of tiger stripes and leopard rosettes for comparison with individuals in CWS’ long-term database. As in the case of tiger mortality, they also provide details of the origin, past history, relatedness, confirmed age and any other pertinent information in the case of individuals that come into conflict with human communities, or disperse into human-dominated areas, so that management actions are informed by the best available scientific information.
CWS scientists, in collaboration with scientific partners in premier research institutes worldwide, have also contributed immensely to the development of methodologies for researching and monitoring wildlife populations. An incomplete list includes the development of camera trap sampling of tigers and leopards within a capture–recapture framework, protocols for faecal DNA-based species identification of wild tigers, Bayesian approaches to spatial capture–recapture analysis, software for automated comparison and matching of tiger stripe and leopard rosette patterns, software for analysis of spatial capture–recapture data, statistical models for analysis of data from occupancy sampling using spatial replication, faecal DNA-based individual identification of tigers and estimation within a capture–recapture framework, statistical methods to combine camera trap-based and faecal DNA-based tiger captures within a spatial capture–recapture framework, application of abundance-induced heterogeneity occupancy models to estimate prey abundance, examination and determination of statistical relationship between tigers – tiger sign, Bayesian continuous-time spatial capture–recapture models, approaches to estimating tiger abundance at large spatial scales combining data sources, use of single-nucleotide polymorphism (SNP) markers to estimate and understand tiger meta-populations, among many others.
These numerous and varied insights into the ecology and conservation of large predators and their prey, as well as the many methodological developments that the study team scientists have pioneered have been widely disseminated among the larger scientific community, park managers and the general public, through a variety of fora. In terms of scientific publications, CWS scientists have published over 85 (and counting!) peer-reviewed papers on tigers and their prey in international scientific journals and published multi-authored technical manuals (including the recently published Methods for Monitoring Tiger and Prey Populations, edited by K. U. Karanth & J. D. Nichols).