The Fate of Wild Tigers

BioScience, Journal Year: 2007, Volume and Issue: 57(6), P. 508 - 514

Published: June 1, 2007

Wild tigers are in a precarious state. Habitat loss and intense poaching of their prey, coupled with inadequate government efforts to maintain tiger populations, have resulted dramatic range contraction populations. Tigers now occupy 7 percent historical range, the past decade, area occupied by has decreased as much 41 percent, according some estimates. If survive into next century, all governments throughout species' must demonstrate greater resolve lasting commitments conserve habitats, well stop trade products from wild captive-bred sources. Where national governments, supported part NGOs (nongovernmental organizations), make consistent substantial commitment conservation, do recover. We urge leaders tiger-range countries support help stage regional summit for establishing collaborative conservation ensure that habitats protected perpetuity.

Language: Английский

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The predator-prey power law: Biomass scaling across terrestrial and aquatic biomes

Science, Journal Year: 2015, Volume and Issue: 349(6252)

Published: Sept. 3, 2015

A general scaling law for ecology Despite the huge diversity of ecological communities, they can have unexpected patterns in common. Hatton et al. describe a that relates total predator and prey biomass terrestrial aquatic animal communities (see Perspective by Cebrian). They draw on data from many thousands population counts ranging plankton to large mammals, across wide range biomes. find ubiquitous pattern scaling, which may suggest an underlying organization ecosystems. It seems follow systematic changes structure dynamics environmental gradients. Science , this issue 10.1126/science.aac6284 ; see also p. 1053

Language: Английский

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Interactions between protected areas and their surroundings in human-dominated tropical landscapes

Biological Conservation, Journal Year: 2010, Volume and Issue: 143(12), P. 2870 - 2880

Published: March 15, 2010

Language: Английский

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Monitoring carnivore populations at the landscape scale: occupancy modelling of tigers from sign surveys

Journal of Applied Ecology, Journal Year: 2011, Volume and Issue: 48(4), P. 1048 - 1056

Published: May 11, 2011

1. Assessing spatial distributions of threatened large carnivores at landscape scales poses formidable challenges because their rarity and elusiveness. As a consequence logistical constraints, investigators typically rely on sign surveys. Most survey methods, however, do not explicitly address the central problem imperfect detections animal signs in field, leading to underestimates true habitat occupancy distribution. 2. We assessed for tiger Panthera tigris metapopulation across c. 38 000-km2 India, employing spatially replicated detections. Ecological predictions about presence were confronted with detection data generated from sampling 205 sites, each 188 km2. 3. A recent model that considers Markovian dependency among replicates performed better than standard (ΔAIC = 184·9). formulation this fitted best showed density ungulate prey levels human disturbance key determinants local presence. Model averaging resulted replicate-level probability 0·17 (0·17) estimate 0·665 (0·0857) or 14 076 (1814) km2 potential 21 167 In contrast, traditional presence-versus-absence approach underestimated by 47%. Maps probabilities site clearly identified source populations higher densities matched observed variations, suggesting utility population assessments scales. 4. Synthesis applications. Landscape-scale surveys can efficiently assess carnivore elucidate factors governing presence, provided ecological observation processes are both modelled. Occupancy using be used reliably identify sources help monitor metapopulations. Our results reinforce earlier findings depletion drivers extinctions tigers persist even human-dominated landscapes through effective protection populations. facilitates efficient targeting conservation interventions and, more generally, provides basis reliable integration monitoring between

Language: Английский

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Tigers on trails: occupancy modeling for cluster sampling

Ecological Applications, Journal Year: 2010, Volume and Issue: 20(5), P. 1456 - 1466

Published: June 22, 2010

Occupancy modeling focuses on inference about the distribution of organisms over space, using temporal or spatial replication to allow detection process. Inference based strictly requires that replicates be selected randomly and with replacement, but importance these design requirements is not well understood. This paper an increasingly popular sampling are expected exhibit Markovian dependence. We develop two new occupancy models for data collected under this sort design, one underlying Markov model dependence other a trap response detections. then simulated fit standard models. Bias estimates was substantial models, smaller model, negligible process model. also from large‐scale tiger survey recently conducted in Karnataka State, southwestern India. In addition providing evidence positive relationship between habitat, selection statistics strongly supported use provides another tool decomposition process, which sometimes needed proper estimation may permit interesting biological inferences. designs employing replication, we note likely existence many replication. The developed here will useful either directly, minor extensions, as well. believe represent important additions suite tools now available conservation monitoring. More generally, work represents contribution topic cluster situations there need specific (e.g., reflecting dependence) variable(s) interest among subunits.

Language: Английский

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Spatio-temporal interactions facilitate large carnivore sympatry across a resource gradient

Proceedings of the Royal Society B Biological Sciences, Journal Year: 2017, Volume and Issue: 284(1848), P. 20161860 - 20161860

Published: Feb. 8, 2017

Species within a guild vary their use of time, space and resources, thereby enabling sympatry. As intra-guild competition intensifies, such behavioural adaptations may become prominent. We assessed mechanisms facilitating sympatry among dhole ( Cuon alpinus ), leopard Panthera pardus ) tiger tigris in tropical forests India using camera-trap surveys. examined population-level temporal, spatial spatio-temporal segregation them across four reserves representing gradient carnivore prey densities. Temporal overlaps were higher at lower Combined overlap was minimal, possibly due to chance. found fine-scale avoidance behaviours one high-density reserve. Our results suggest that: (i) patterns spatial, temporal sympatric carnivores do not necessarily mirror each other; (ii) are likely adopt as alternative facilitate sympatry; (iii) show adaptability resource availability, driver inter-species competition. discuss that permit co-occupy rather than dominate functional niches, varying intensities shape structure dynamics guilds.

Language: Английский

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A hierarchical model for estimating density in camera‐trap studies

Journal of Applied Ecology, Journal Year: 2008, Volume and Issue: 46(1), P. 118 - 127

Published: Nov. 20, 2008

Summary Estimating animal density using capture–recapture data from arrays of detection devices such as camera traps has been problematic due to the movement individuals and heterogeneity in capture probability among them induced by differential exposure trapping. We develop a spatial model for estimating camera‐trapping which contains explicit models point process governing distribution their traps. adopt Bayesian approach analysis hierarchical technique augmentation. The is applied photographic on tigers Panthera tigris Nagarahole reserve, India. Using this model, we estimate be 14·3 animals per 100 km 2 during 2004. Synthesis applications. Our modelling framework largely overcomes several weaknesses conventional approaches estimation trap arrays. It effectively deals with key problems individual probabilities, traps, presence potential ‘holes’ array ad hoc sample area. formulation, thus, greatly enhances flexibility conduct field surveys well data, studies that may involve physical, or DNA‐based ‘captures’ animals.

Language: Английский

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Assessing the viability of tiger subpopulations in a fragmented landscape

Journal of Applied Ecology, Journal Year: 2006, Volume and Issue: 43(3), P. 576 - 586

Published: March 29, 2006

Summary Conservation managers require accurate and timely information on the occurrence, size viability of populations, but this is often difficult for cryptic species living at low densities over large areas. This study aimed to provide such tigers in 36 400‐km 2 Kerinci Seblat (KS) region, Sumatra, by identifying assessing subpopulation under different management strategies. Tiger occurrence was mapped within a geographical system (GIS) using repeat detection–non‐detection surveys incorporate function detection probability into logistic regression model. The landscape variables that influenced tiger occupancy were then used construct spatially explicit habitat model identify core number each area estimated calculating forest types their respective as determined through camera trapping. assessed scenarios population analysis (PVA). negatively correlated with distance public roads. Four areas identified, all predominantly located KS National Park, support subpopulations 21, 105, 16 three adult tigers, respectively. PVA showed larger could be demographically viable if well protected. However, poaching removed ≥ 3 per year, only largest would not reach extinction 50 years. Connectivity ensure survival smaller subpopulations, providing source offset losses. Synthesis applications. Our key recommendations region Sumatra stress importance maintaining connectivity between area, minimizing these More widely, our research has shown feasibility combined spatial modelling conservation management.

Language: Английский

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Diet and prey profiles of three sympatric large carnivores in Bandipur Tiger Reserve, India

Journal of Zoology, Journal Year: 2007, Volume and Issue: 273(2), P. 169 - 175

Published: June 29, 2007

Abstract We conducted a field study of diets three sympatric large carnivores, the tiger Panthera tigris , leopard pardus and dhole Cuon alpinus in Bandipur Tiger Reserve, India, based on analyses 381, 111 181 scats, respectively. The frequency occurrence prey items scats was converted to relative biomass number consumed using regression equations earlier feeding trials. results showed that although these predators kill ∼11–15 species vertebrate prey, relatively abundant ungulate provide 88–97% by them. Although dietary niche overlap among high (Pianka's index 0.75–0.93), some specialized predation observed. largest ungulates, gaur Bos gaurus sambar Cervus unicolor provided 73% tigers, whereas medium‐sized chital Axis axis wild pig Sus scrofa formed 65 83% intake leopards dholes, In terms numbers animals killed predators, chital, which is most species, dominated their (tiger=33%, leopard=39% dhole=73%). study, conjunction with work, support prediction abundance as well availability different size classes, are both critical factors facilitate sympatry predators.

Language: Английский

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The impact on tigers of poaching versus prey depletion

Journal of Applied Ecology, Journal Year: 2008, Volume and Issue: 45(6), P. 1667 - 1674

Published: Aug. 22, 2008

Summary There exists a continuing dilemma in prioritizing conservation actions for large carnivores. Habitat loss, poaching, and prey depletion have often been cited as the three primary threats, but there is debate over relative importance of each. We assess poaching rates, use existing information literature multi‐type branching process deterministic felid population models to address four lines evidence used infer that tiger populations are inherently resilient high mortality rates. Our results suggest tigers, more so than leopards or cougars, require persist, quite susceptible modest increases mortality, less likely recover quickly after declines. Demographic responses would ensure persistence with rates sustainable cougars biologically unrealistic tigers. propose alternative interpretations tigers In contrast other solitary felids, breed later their inter‐birth interval larger, making them poaching. A model support contention has greater impact on appears be based false premises. Camera‐trapping data positive growth despite low survival rate cannot differentiate from emigration, does not varying different sex‐age classes; example, dispersers tolerable if adult breeding females high. Synthesis applications. While numbers essential sustain populations, our recovery efforts will sufficient reach 15%. Extrapolating demographic other, even closely related species develop strategies can misleading. Reduction human‐caused especially resident females, most short‐term effort must made. Since usually unknown generally stochastic nature, any management policy might reduce should firmly avoided.

Language: Английский

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