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Miller DL, Fifield D, Wakefield E, Sigourney DB. Extending density surface models to include multiple and double-observer survey data. PeerJ 2021; 9:e12113. [PMID: 34557355 PMCID: PMC8418794 DOI: 10.7717/peerj.12113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/14/2021] [Indexed: 11/30/2022] Open
Abstract
Spatial models of density and abundance are widely used in both ecological research (e.g., to study habitat use) and wildlife management (e.g., for population monitoring and environmental impact assessment). Increasingly, modellers are tasked with integrating data from multiple sources, collected via different observation processes. Distance sampling is an efficient and widely used survey and analysis technique. Within this framework, observation processes are modelled via detection functions. We seek to take multiple data sources and fit them in a single spatial model. Density surface models (DSMs) are a two-stage approach: first accounting for detectability via distance sampling methods, then modelling distribution via a generalized additive model. However, current software and theory does not address the issue of multiple data sources. We extend the DSM approach to accommodate data from multiple surveys, collected via conventional distance sampling, double-observer distance sampling (used to account for incomplete detection at zero distance) and strip transects. Variance propagation ensures that uncertainty is correctly accounted for in final estimates of abundance. Methods described here are implemented in the dsm R package. We briefly analyse two datasets to illustrate these new developments. Our new methodology enables data from multiple distance sampling surveys of different types to be treated in a single spatial model, enabling more robust abundance estimation, potentially over wider geographical or temporal domains.
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Affiliation(s)
- David L Miller
- Centre for Research into Ecological and Environmental Modelling and School of Mathematics and Statistics, University of St Andrews, St Andrews, Scotland
| | - David Fifield
- Wildlife Research Division, Science and Technology Branch, Environment and Climate Change Canada, Mount Pearl, NL, Canada
| | - Ewan Wakefield
- Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, Scotland
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Gogoi K, Kumar U, Banerjee K, Jhala YV. Spatially explicit density and its determinants for Asiatic lions in the Gir forests. PLoS One 2020; 15:e0228374. [PMID: 32074110 PMCID: PMC7029878 DOI: 10.1371/journal.pone.0228374] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 01/14/2020] [Indexed: 12/05/2022] Open
Abstract
Asiatic lions (Panthera leo persica) are an icon of conservation success, yet their status is inferred from total counts that cannot account for detection bias and double counts. With an effort of 4,797 km in 725 km2 of western Gir Protected Area, India, we used polygon search based spatially explicit capture recapture framework to estimate lion density. Using vibrissae patterns and permanent body marks we identified 67 lions from 368 lion sightings. We conducted distance sampling on 35 transects with an effort of 101.5 km to estimate spatial prey density using generalized additive modeling (GAM). Subsequently, we modeled lion spatial density with prey, habitat characteristics, anthropogenic factors and distance to baiting sites. Lion density (>1-year-old lions) was estimated at 8.53 (SE 1.05) /100 km2 with lionesses having smaller movement parameter (σ = 2.55 km; SE 0.12) compared to males (σ = 5.32 km; SE 0.33). Detection corrected sex ratio (female:male lions) was 1.14 (SE 0.02). Chital (Axis axis) was the most abundant ungulate with a density of 63.29 (SE 10.14) as determined by conventional distance sampling (CDS) and 58.17 (SE 22.17)/km2 with density surface modeling (DSM), followed by sambar (Rusa unicolor) at 3.84 (SE 1.07) and 4.73 (SE 1.48)/km2 estimated by CDS and DSM respectively. Spatial lion density was best explained by proximity to baiting sites and flat valley habitat but not as much by prey density. We demonstrate a scientifically robust approach to estimate lion abundance, that due to its spatial context, can be useful for management of habitat and human-lion interface. We recommend this method for lion population assessment across their range. High lion densities in western Gir were correlated with baiting. The management practice of attracting lions for tourism can perturb natural lion densities, disrupt behavior, lion social dynamics and have detrimental effects on local prey densities.
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Affiliation(s)
- Keshab Gogoi
- Wildlife Institute of India, Chandrabani, Dehradun, Uttarakhand, India
| | - Ujjwal Kumar
- Wildlife Institute of India, Chandrabani, Dehradun, Uttarakhand, India
| | - Kausik Banerjee
- Wildlife Institute of India, Chandrabani, Dehradun, Uttarakhand, India
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Carter NH, Levin SA, Grimm V. Effects of human-induced prey depletion on large carnivores in protected areas: Lessons from modeling tiger populations in stylized spatial scenarios. Ecol Evol 2019; 9:11298-11313. [PMID: 31641474 PMCID: PMC6802045 DOI: 10.1002/ece3.5632] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 07/30/2019] [Accepted: 08/01/2019] [Indexed: 11/17/2022] Open
Abstract
Prey depletion is a major threat to the conservation of large carnivore species globally. However, at the policy-relevant scale of protected areas, we know little about how the spatial distribution of prey depletion affects carnivore space use and population persistence. We developed a spatially explicit, agent-based model to investigate the effects of different human-induced prey depletion experiments on the globally endangered tiger (Panthera tigris) in isolated protected areas-a situation that prevails throughout the tiger's range. Specifically, we generated 120 experiments that varied the spatial extent and intensity of prey depletion across a stylized (circle) landscape (1,000 km2) and Nepal's Chitwan National Park (~1,239 km2). Experiments that created more spatially homogenous prey distributions (i.e., less prey removed per cell but over larger areas) resulted in larger tiger territories and smaller population sizes over time. Counterintuitively, we found that depleting prey along the edge of Chitwan National Park, while decreasing tiger numbers overall, also decreased female competition for those areas, leading to lower rates of female starvation. Overall our results suggest that subtle differences in the spatial distributions of prey densities created by various human activities, such as natural resource-use patterns, urban growth and infrastructure development, or conservation spatial zoning might have unintended, detrimental effects on carnivore populations. Our model is a useful planning tool as it incorporates information on animal behavioral ecology, resource spatial distribution, and the drivers of change to those resources, such as human activities.
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Affiliation(s)
- Neil H. Carter
- School for Environment and SustainabilityUniversity of MichiganAnn ArborMIUSA
| | - Simon A. Levin
- Department of Ecology & Evolutionary BiologyPrinceton UniversityPrincetonNJUSA
| | - Volker Grimm
- Department of Ecological ModellingHelmholtz Centre for Environmental Research – UFZLeipzigGermany
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Harihar A, Chanchani P, Borah J, Crouthers RJ, Darman Y, Gray TNE, Mohamad S, Rawson BM, Rayan MD, Roberts JL, Steinmetz R, Sunarto S, Widodo FA, Anwar M, Bhatta SR, Chakravarthi JPP, Chang Y, Congdon G, Dave C, Dey S, Durairaj B, Fomenko P, Guleria H, Gupta M, Gurung G, Ittira B, Jena J, Kostyria A, Kumar K, Kumar V, Lhendup P, Liu P, Malla S, Maurya K, Moktan V, Van NDN, Parakkasi K, Phoonjampa R, Phumanee W, Singh AK, Stengel C, Subba SA, Thapa K, Thomas TC, Wong C, Baltzer M, Ghose D, Worah S, Vattakaven J. Recovery planning towards doubling wild tiger Panthera tigris numbers: Detailing 18 recovery sites from across the range. PLoS One 2018; 13:e0207114. [PMID: 30408090 PMCID: PMC6224104 DOI: 10.1371/journal.pone.0207114] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 10/23/2018] [Indexed: 11/18/2022] Open
Abstract
With less than 3200 wild tigers in 2010, the heads of 13 tiger-range countries committed to doubling the global population of wild tigers by 2022. This goal represents the highest level of ambition and commitment required to turn the tide for tigers in the wild. Yet, ensuring efficient and targeted implementation of conservation actions alongside systematic monitoring of progress towards this goal requires that we set site-specific recovery targets and timelines that are ecologically realistic. In this study, we assess the recovery potential of 18 sites identified under WWF's Tigers Alive Initiative. We delineated recovery systems comprising a source, recovery site, and support region, which need to be managed synergistically to meet these targets. By using the best available data on tiger and prey numbers, and adapting existing species recovery frameworks, we show that these sites, which currently support 165 (118-277) tigers, have the potential to harbour 585 (454-739) individuals. This would constitute a 15% increase in the global population and represent over a three-fold increase within these specific sites, on an average. However, it may not be realistic to achieve this target by 2022, since tiger recovery in 15 of these 18 sites is contingent on the initial recovery of prey populations, which is a slow process. We conclude that while sustained conservation efforts can yield significant recoveries, it is critical that we commit our resources to achieving the biologically realistic targets for these sites even if the timelines are extended.
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Affiliation(s)
| | | | - Jimmy Borah
- WWF-India, Assam, India
- WWF-Greater Mekong Program, Phnom Penh, Cambodia
| | | | - Yury Darman
- WWF-Russia, Amur branch, Vladivostok, Russia
| | | | | | | | - Mark Darmaraj Rayan
- WWF-Malaysia, Kuala Lumpur, Selangor, Malaysia
- Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, United Kingdom
| | | | | | | | | | - Meraj Anwar
- WWF-India, Terai Arc Landscape Office, Haldwani, Uttarakhand, India
| | | | | | - Youde Chang
- WWF-China, Changchun, Jilin Province, P. R. China
| | | | - Chittaranjan Dave
- WWF-India, Satpura Maikal Landscape Office, Mandla, Madhya Pradesh, India
| | - Soumen Dey
- WWF-India, Satpura Maikal Landscape Office, Jabalpur, Madhya Pradesh, India
| | - Boominathan Durairaj
- WWF-India, Western Ghats Nilgiris Landscape Office, Coimbatore, Tamil Nadu, India
| | | | - Harish Guleria
- WWF-India, Terai Arc Landscape Office, Haldwani, Uttarakhand, India
| | - Mudit Gupta
- WWF-India Terai Arc Landscape Office, Pilibhit, Uttar Pradesh, India
| | | | - Bopanna Ittira
- WWF-India, Programme Office, Dehradun, Uttarakhand, India
| | - Jyotirmay Jena
- WWF-India, Satpura Maikal Landscape Office, Balaghat, Madhya Pradesh, India
| | | | - Krishna Kumar
- WWF-India, Western Ghats Nilgiris Landscape Office, Coimbatore, Tamil Nadu, India
| | - Vijay Kumar
- WWF-India, Western Ghats Nilgiris Landscape Office, Bhavanisagar, Tamil Nadu, India
| | | | - Peiqi Liu
- WWF-China, Changchun, Jilin Province, P. R. China
| | | | - Kamlesh Maurya
- WWF-India Terai Arc Landscape Office, Pilibhit, Uttar Pradesh, India
| | | | | | | | | | | | | | - Carrie Stengel
- WWF-Tigers Alive Initiative, Washington-D.C., United States of America
| | | | | | - Tiju C. Thomas
- WWF-India, Western Ghats Nilgiris Landscape Office, Coimbatore, Tamil Nadu, India
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