The use of distance sampling and mark-resight to estimate the local density of wildlife populations

2002 ◽  
Vol 13 (2) ◽  
pp. 177-186 ◽  
Author(s):  
Stefano Focardi ◽  
Roberto Isotti ◽  
Elisabetta Raganella Pelliccioni ◽  
Daniele Iannuzzo
Keyword(s):  
Local Density ◽  
Distance Sampling ◽  
Wildlife Populations

scholarly journals Protected by dragons: Density surface modeling confirms large population of the critically endangered Yellow-crested Cockatoo on Komodo Island

The Condor ◽  
2020 ◽  
Author(s):  
Anna Reuleaux ◽  
Benny A Siregar ◽  
Nigel J Collar ◽  
Maria R Panggur ◽  
Ani Mardiastuti ◽  
...  
Keyword(s):  
Population Size ◽  
Local Density ◽  
Large Population ◽  
Distance Sampling ◽  
Surface Modeling ◽  
Habitat Associations ◽  
Critically Endangered ◽  
Topographic Wetness Index ◽  
Monsoon Forest ◽  
Density Surface

Abstract Intense trapping of the critically endangered Yellow-crested Cockatoo (Cacatua sulphurea) for the international pet trade has devastated its populations across Indonesia such that populations of >100 individuals remain at only a handful of sites. We combined distance sampling with density surface modeling (DSM) to predict local densities and estimate total population size for one of these areas, Komodo Island, part of Komodo National Park (KNP) in Indonesia. We modeled local density based on topography (topographic wetness index) and habitat types (percentage of palm savanna and deciduous monsoon forest). Our population estimate of 1,113 (95% CI: 587–2,109) individuals on Komodo Island was considerably larger than previous conservative estimates. Our density surface maps showed cockatoos to be absent over much of the island, but present at high densities in wooded valleys. Coincidence between our DSM and a set of independent cockatoo observations was high (93%). Standardized annual counts by KNP staff in selected areas of the island showed increases in cockatoo records from <400 in 2011 to ~650 in 2017. Taken together, our results indicate that KNP, alongside and indeed because of preserving its iconic Komodo dragons (Varanus komodoensis), is succeeding in protecting a significant population of Indonesia’s rarest cockatoo species. To our knowledge this is the first time DSM has been applied to a critically endangered species. Our findings highlight the potential of DSM for locating abundance hotspots, identifying habitat associations, and estimating global population size in a range of threatened taxa, especially if independent datasets can be used to validate model predictions.

scholarly journals Sound level measurements from audio recordings provide objective distance estimates for distance sampling wildlife populations

2019 ◽  
Vol 6 (3) ◽  
pp. 301-315 ◽  
Author(s):  
Daniel A. Yip ◽  
Elly C. Knight ◽  
Elène Haave‐Audet ◽  
Scott J. Wilson ◽  
Connor Charchuk ◽  
...  
Keyword(s):  
Distance Sampling ◽  
Sound Level ◽  
Audio Recordings ◽  
Objective Distance ◽  
Wildlife Populations

scholarly journals A Unifying Model for Capture–Recapture and Distance Sampling Surveys of Wildlife Populations

2015 ◽  
Vol 110 (509) ◽  
pp. 195-204 ◽  
Author(s):  
D. L. Borchers ◽  
B. C. Stevenson ◽  
D. Kidney ◽  
L. Thomas ◽  
T. A. Marques
Keyword(s):  
Distance Sampling ◽  
Capture Recapture ◽  
Wildlife Populations

scholarly journals The Long-term Impacts of Hunting on Population Viability of Wild Ungulates in Tarangire, Northern Tanzania

2021 ◽  
Author(s):  
◽  
Alfan Abeid Rija
Keyword(s):  
Distance Sampling ◽  
Research Priorities ◽  
Wild Ungulates ◽  
Illegal Hunting ◽  
Northern Tanzania ◽  
Population Sizes ◽  
Wildlife Populations ◽  
Average Size ◽  
Response Method

<p>Hunting through illegal and legal means is increasingly recognised as a threat to the sustainability of wildlife populations in reserves throughout Africa. Despite this, in Tanzania, legal hunting has persisted and serves as a source of revenue for conserving these species. Poaching remains a major threat to wildlife populations in many parks and reserves of Tanzania and wildlife habitats are diminishing due to human activities. I examined the impacts of hunting on the long-term persistence of four wild ungulates; impala (Aepyceros melampus Matschie), Thomson's gazelle (Gazella thomsonii Gunther), wildebeest (Connochaetes taurinus Thomas) and zebra (Equus burchellii Matschie) around Tarangire National Park, in northern Tanzania. I investigated the population sizes of these species using Distance sampling method and determined there were 4534 plus or minus 1393 impala 1398 plus or minus 491 Thomson's gazelle, 5199 plus or minus 2670 wildebeest, and 11223 plus or minus 4216 zebra, in the study area. I obtained an estimate of the legal offtake over a five year period from data provided by hunting companies and districts offices in charge of hunting in the area to establish an average size of annual legal offtake of the area. I estimated the poaching levels for each species using random response method by interviewing 298 household respondents within communities living around the area. This established that illegal kill were 2-3 times higher than legal offtake for all four animal species except zebra. The total annual harvests were 6.6% for impala, 18.2% for Thomson's gazelle, 5.2% for wildebeest and 2% for zebra, of population sizes. Using literature review I obtained vital life-history parameters for each species either from within Tarangire, or elsewhere in East Africa. The long-term viability of the four species was then examined under a computer program-VORTEX by constructing a series of models to test the effects of different hunting regimes. The models integrated mortality and fecundity rates, species population sizes and harvest (legal and illegal) rates. Of the four species, impala and Thomson's gazelle fared badly under all simulations, with up to 76% and 68% respectively of the modelled populations going extinct within 100 years under present 3 hunting levels. Wildebeest and zebra were more resilient to hunting. Zebra populations remained robust under current hunting rates. However, its population will slowly decline towards extinction when the hunting exceeds the current rate of 2%. The population of wildebeest will decline towards extinction if the current offtake of 5% persists. The impacts of illegal hunting are severe. This study is the first attempt to characterise the dynamics of the harvested ungulate populations in Tarangire, Tanzania. Poor understanding of this ecosystem especially on the demographic variables of these species, limit firm conclusions. Nevertheless, the findings presented here suggest that VORTEX modelling may be a useful tool for managing hunting at Tarangire and for highlighting research priorities.</p>

scholarly journals Using encounter rates as surrogates for density estimates makes monitoring of heavily-traded grey parrots achievable across Africa

Oryx ◽  
2015 ◽  
Vol 50 (4) ◽  
pp. 617-625 ◽  
Author(s):  
Stuart J. Marsden ◽  
Emmanuel Loqueh ◽  
Jean Michel Takuo ◽  
John A. Hart ◽  
Robert Abani ◽  
...  
Keyword(s):  
Local Density ◽  
Conservation Status ◽  
Distance Sampling ◽  
Central Africa ◽  
High Mobility ◽  
Encounter Rate ◽  
Line Transect ◽  
African Countries ◽  
Density Estimates ◽  
Encounter Rates

AbstractEstimating population sizes in the heavily traded grey parrots of West and Central Africa would provide insights into conservation status and sustainability of harvests. Ideally, density estimates would be derived from a standardized method such as distance sampling, but survey efforts are hampered by the extensive ranges, patchy distribution, variable abundance, cryptic habits and high mobility of the parrots as well as by logistical difficulties and limited resources. We carried out line transect distance sampling alongside a simpler encounter rate method at 10 sites across five West and Central African countries. Density estimates were variable across sites, from 0–0.5 individuals km−2 in Côte d'Ivoire and central Democratic Republic of the Congo to c. 30 km−2 in Cameroon and > 70 km−2 on the island of Príncipe. Most significantly, we identified the relationship between densities estimated from distance sampling and simple encounter rates, which has important applications in monitoring grey parrots: (1) to convert records of parrot groups encountered in a day's activities by anti-poaching patrols within protected areas into indicative density estimates, (2) to confirm low density in areas where parrots are so rare that distance sampling is not feasible, and (3) to provide a link between anecdotal records and local density estimates. Encounter rates of less than one parrot group per day of walking are a reality in most forests within the species’ ranges. Densities in these areas are expected to be one individual km−2 or lower, and local harvest should be disallowed on this basis.

Correcting wildlife counts using detection probabilities

2005 ◽  
Vol 32 (3) ◽  
pp. 211 ◽  
Author(s):  
Gary C. White
Keyword(s):  
Detection Probability ◽  
Distance Sampling ◽  
Probability Of Detection ◽  
Mark Recapture ◽  
Additional Information ◽  
Release Studies ◽  
Detection Probabilities ◽  
Minimum Number ◽  
Capture And Release ◽  
Wildlife Populations

One of the most pervasive uses of indices of wildlife populations is uncorrected counts of animals. Two examples are the minimum number known alive from capture and release studies, and aerial surveys where the detection probability is not estimated from a sightability model, marked animals, or distance sampling. Both the mark–recapture and distance-sampling estimators are techniques to estimate the probability of detection of an individual animal (or cluster of animals), which is then used to correct a count of animals. However, often the number of animals in a survey is inadequate to compute an estimate of the detection probability and hence correct the count. Modern methods allow sophisticated modelling to estimate the detection probability, including incorporating covariates to provide additional information about the detection probability. Examples from both distance and mark–recapture sampling are presented to demonstrate the approach.

scholarly journals The Long-term Impacts of Hunting on Population Viability of Wild Ungulates in Tarangire, Northern Tanzania

2021 ◽  
Author(s):  
◽  
Alfan Abeid Rija
Keyword(s):  
Distance Sampling ◽  
Research Priorities ◽  
Wild Ungulates ◽  
Illegal Hunting ◽  
Northern Tanzania ◽  
Population Sizes ◽  
Wildlife Populations ◽  
Average Size ◽  
Response Method

<p>Hunting through illegal and legal means is increasingly recognised as a threat to the sustainability of wildlife populations in reserves throughout Africa. Despite this, in Tanzania, legal hunting has persisted and serves as a source of revenue for conserving these species. Poaching remains a major threat to wildlife populations in many parks and reserves of Tanzania and wildlife habitats are diminishing due to human activities. I examined the impacts of hunting on the long-term persistence of four wild ungulates; impala (Aepyceros melampus Matschie), Thomson's gazelle (Gazella thomsonii Gunther), wildebeest (Connochaetes taurinus Thomas) and zebra (Equus burchellii Matschie) around Tarangire National Park, in northern Tanzania. I investigated the population sizes of these species using Distance sampling method and determined there were 4534 plus or minus 1393 impala 1398 plus or minus 491 Thomson's gazelle, 5199 plus or minus 2670 wildebeest, and 11223 plus or minus 4216 zebra, in the study area. I obtained an estimate of the legal offtake over a five year period from data provided by hunting companies and districts offices in charge of hunting in the area to establish an average size of annual legal offtake of the area. I estimated the poaching levels for each species using random response method by interviewing 298 household respondents within communities living around the area. This established that illegal kill were 2-3 times higher than legal offtake for all four animal species except zebra. The total annual harvests were 6.6% for impala, 18.2% for Thomson's gazelle, 5.2% for wildebeest and 2% for zebra, of population sizes. Using literature review I obtained vital life-history parameters for each species either from within Tarangire, or elsewhere in East Africa. The long-term viability of the four species was then examined under a computer program-VORTEX by constructing a series of models to test the effects of different hunting regimes. The models integrated mortality and fecundity rates, species population sizes and harvest (legal and illegal) rates. Of the four species, impala and Thomson's gazelle fared badly under all simulations, with up to 76% and 68% respectively of the modelled populations going extinct within 100 years under present 3 hunting levels. Wildebeest and zebra were more resilient to hunting. Zebra populations remained robust under current hunting rates. However, its population will slowly decline towards extinction when the hunting exceeds the current rate of 2%. The population of wildebeest will decline towards extinction if the current offtake of 5% persists. The impacts of illegal hunting are severe. This study is the first attempt to characterise the dynamics of the harvested ungulate populations in Tarangire, Tanzania. Poor understanding of this ecosystem especially on the demographic variables of these species, limit firm conclusions. Nevertheless, the findings presented here suggest that VORTEX modelling may be a useful tool for managing hunting at Tarangire and for highlighting research priorities.</p>

Ab initio band theory approach to electron energy loss near edge structures

1988 ◽  
Vol 46 ◽  
pp. 506-507
Author(s):  
Xudong Weng ◽  
O.F. Sankey ◽  
Peter Rez
Keyword(s):  
Ab Initio ◽  
Local Density ◽  
Interpolation Method ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Large Set ◽  
Theory Approach ◽  
Band Theory ◽  
Atomic Orbitals ◽  
Pseudopotential Calculations

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.

Flux-pinning-related defect structures in melt-processed YBa2Cu3O7-x

1993 ◽  
Vol 51 ◽  
pp. 936-937
Author(s):  
Z. L. Wang ◽  
R. Kontra ◽  
A. Goyal ◽  
D. M. Kroeger ◽  
L.F. Allard
Keyword(s):  
Volume Fraction ◽  
Local Density ◽  
Stacking Faults ◽  
Image Resolution ◽  
Defect Structures ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Point Image ◽  
Related Defect ◽  
Point To Point

Previous studies of Y2BaCuO5/YBa2Cu3O7-δ(Y211/Y123) interfaces in melt-processed and quench-melt-growth processed YBa2Cu3O7-δ using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) have revealed a high local density of stacking faults in Y123, near the Y211/Y123 interfaces. Calculations made using simple energy considerations suggested that these stacking faults may act as effective flux-pinners and may explain the observations of increased Jc with increasing volume fraction of Y211. The present paper is intended to determine the atomic structures of the observed defects. HRTEM imaging was performed using a Philips CM30 (300 kV) TEM with a point-to-point image resolution of 2.3 Å. Nano-probe EDS analysis was performed using a Philips EM400 TEM/STEM (100 kV) equipped with a field emission gun (FEG), which generated an electron probe of less than 20 Å in diameter.Stacking faults produced by excess single Cu-O layers: Figure 1 shows a HRTEM image of a Y123 film viewed along [100] (or [010]).

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