Abstract
Occupying only 7% of their historical range and confined to forested habitats interspersed in a matrix of human dominated landscapes, tigers (Panthera tigris) typify the problems faced by most large carnivores worldwide. With heads of governments of tiger range countries pledging to reverse the extinction process and setting a goal of doubling wild tiger numbers by 2022, achieving this target would require identifying existing breeding cores, potential breeding habitats and opportunities for dispersal. The Terai Arc Landscape (TAL) represents one region which has recently witnessed recovery of tiger populations following conservation efforts. In this study, we develop a spatially explicit tiger occupancy model with survey data from 2009–10 based on a priori knowledge of tiger biology and specific issues plaguing the western TAL (6,979 km2), which occurs in two disjunct units (Tiger Habitat Blocks; THBs). Although the overall occupancy of tigers was 0.588 (SE 0.071), our results clearly indicate that loss in functionality of a regional corridor has resulted in tigers now occupying 17.58% of the available habitat in THB I in comparison to 88.5% in THB II. The current patterns of occupancy were best explained by models incorporating the interactive effect of habitat blocks (AIC w = 0.883) on wild prey availability (AIC w = 0.742) and anthropogenic disturbances (AIC w = 0.143). Our analysis has helped identify areas of high tiger occupancy both within and outside existing protected areas, which highlights the need for a unified control of the landscape under a single conservation unit with the primary focus of managing tigers and associated wildlife. Finally, in the light of global conservation targets and recent legislations in India, our study assumes significance as we identify opportunities to secure (e.g. THB II) and increase (e.g. THB I) tiger populations in the landscape.
Highlights
Fragmentation and the loss of connectivity between suitable habitats have led to range wide population declines among many mammalian species [1]
Studies have demonstrated that effects of fragmentation are most severely realized by larger carnivores, which thereby are not being able to persist in human dominated landscapes with weak or no linkages to suitable habitat tracts [6]. Given their critical role in ecosystems, large carnivores often serve as umbrella species, garnering support for conservation, and serve as effective focal species to assess the impact of anthropogenic disturbances across large landscapes [7]
As we had assumed that surveys could begin on any randomly chosen replicate, we estimated the probability of presence on the first replicate [^h0(SE[^h0])] as 0.394 (0.03) in Tiger Habitat Blocks (THBs) I and 0.794 (0.06) in THB II
Summary
Fragmentation and the loss of connectivity between suitable habitats have led to range wide population declines among many mammalian species [1]. Studies have demonstrated that effects of fragmentation are most severely realized by larger carnivores, which thereby are not being able to persist in human dominated landscapes with weak or no linkages to suitable habitat tracts [6]. Given their critical role in ecosystems, large carnivores often serve as umbrella species, garnering support for conservation, and serve as effective focal species to assess the impact of anthropogenic disturbances across large landscapes [7]. While studies have delineated and prioritized landscapes as the best options for securing tiger metapopulations for long-term conservation [8], ensuring population persistence requires that landscapes remain permeable to tiger movement, and source sites are secured within them [10,11]
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