Estimating western ringtail possum (Pseudocheirus occidentalis) density using distance sampling

2010 ◽  
Vol 32 (2) ◽  
pp. 197 ◽  
Author(s):  
G. R. Finlayson ◽  
A. N. Diment ◽  
P. Mitrovski ◽  
G. G. Thompson ◽  
S. A. Thompson
Keyword(s):  
Urban Development ◽  
Population Size ◽  
Western Australia ◽  
Distance Sampling ◽  
Reliable Estimate ◽  
Population Estimates ◽  
Density Estimates ◽  
The Subject ◽  
Ringtail Possum

A reliable estimate of population size is of paramount importance for making management decisions on species of conservation significance that may be impacted during development. The western ringtail possum (Pseudocheirus occidentalis) is regularly encountered during urban development and is the subject of numerous surveys to estimate its abundance. A variety of techniques have been used for this species with mixed results. This paper reports on a case study using distance sampling to estimate density of P. occidentalis in a small habitat remnant near Busselton, Western Australia. Density estimates obtained were within the range of previous studies of this species and we suggest that this technique should be employed in future surveys to improve the accuracy of population estimates for this species before development.

scholarly journals Improving Estimates of Bird Density Using Multiple- Covariate Distance Sampling

The Auk ◽  
2007 ◽  
Vol 124 (4) ◽  
pp. 1229-1243 ◽  
Author(s):  
Tiago A. Marques ◽  
Len Thomas ◽  
Steven G. Fancy ◽  
Stephen T. Buckland
Keyword(s):  
Distance Sampling ◽  
Probability Of Detection ◽  
Density Estimates ◽  
Bird Density ◽  
Multiple Covariates ◽  
Model Probability ◽  
Point Transect ◽  
Space Distance ◽  
True Population

Abstract Inferences based on counts adjusted for detectability represent a marked improvement over unadjusted counts, which provide no information about true population density and rely on untestable and unrealistic assumptions about constant detectability for inferring differences in density over time or space. Distance sampling is a widely used method to estimate detectability and therefore density. In the standard method, we model the probability of detecting a bird as a function of distance alone. Here, we describe methods that allow us to model probability of detection as a function of additional covariates—an approach available in DISTANCE, version 5.0 (Thomas et al. 2005) but still not widely applied. The main use of these methods is to increase the reliability of density estimates made on subsets of the whole data (e.g., estimates for different habitats, treatments, periods, or species), to increase precision of density estimates or to allow inferences about the covariates themselves. We present a case study of the use of multiple covariates in an analysis of a point-transect survey of Hawaii Amakihi (Hemignathus virens). Amélioration des estimations de densité d’oiseaux par l’utilisation de l’échantillonnage par la distance avec covariables multiples

scholarly journals A grid-based sample design framework for household surveys

2020 ◽  
Vol 4 ◽  
pp. 13 ◽  
Author(s):  
Gianluca Boo ◽  
Edith Darin ◽  
Dana R. Thomson ◽  
Andrew J. Tatem
Keyword(s):  
Random Field ◽  
Population Size ◽  
Sampling Design ◽  
Population Estimates ◽  
Household Surveys ◽  
Design Framework ◽  
Sampling Frame ◽  
Sample Design ◽  
Grid Based

Traditional sample designs for household surveys are contingent upon the availability of a representative primary sampling frame. This is defined using enumeration units and population counts retrieved from decennial national censuses that can become rapidly inaccurate in highly dynamic demographic settings. To tackle the need for representative sampling frames, we propose an original grid-based sample design framework introducing essential concepts of spatial sampling in household surveys. In this framework, the sampling frame is defined based on gridded population estimates and formalized as a bi-dimensional random field, characterized by spatial trends, spatial autocorrelation, and stratification. The sampling design reflects the characteristics of the random field by combining contextual stratification and proportional to population size sampling. A nonparametric estimator is applied to evaluate the sampling design and inform sample size estimation. We demonstrate an application of the proposed framework through a case study developed in two provinces located in the western part of the Democratic Republic of the Congo. We define a sampling frame consisting of settled cells with associated population estimates. We then perform a contextual stratification by applying a principal component analysis (PCA) and k-means clustering to a set of gridded geospatial covariates, and sample settled cells proportionally to population size. Lastly, we evaluate the sampling design by contrasting the empirical cumulative distribution function for the entire population of interest and its weighted counterpart across different sample sizes and identify an adequate sample size using the Kolmogorov-Smirnov distance between the two functions. The results of the case study underscore the strengths and limitations of the proposed grid-based sample design framework and foster further research into the application of spatial sampling concepts in household surveys.

scholarly journals Distribution, abundance and density estimates of franciscanas, Pontoporia blainvillei (Cetacea: Pontoporiidae), in Babitonga bay, southern Brazil

2008 ◽  
Vol 25 (3) ◽  
pp. 397-402 ◽  
Author(s):  
Marta J. Cremer ◽  
Paulo C. Simões-Lopes
Keyword(s):  
Data Collection ◽  
Population Size ◽  
Group Size ◽  
Distance Sampling ◽  
North Coast ◽  
Southern Brazil ◽  
Density Estimates ◽  
The North ◽  
Pontoporia Blainvillei ◽  
Best Fit

Pontoporia blainvillei (Gervais & d'Orbigny, 1844) is threatened throughout its distribution. The species can be found year-round in the Babitonga bay estuary (26º 02'-26º 28'S and 48º28'-48º50'W), in the north coast of the state of Santa Catarina, Brazil. Boat surveys were conducted in order to evaluate its abundance and density between 2000 and 2003. Sampling was random and stratified, with 46 transects in five sub-areas, comprising a total area of 160 km². Data collection was conducted following the linear transect method with distance sampling. A total of 1174.7 km was scanned and 38 groups were observed. Franciscanas were not uniformly distributed in Babitonga bay. Group size ranged from one to 13 animals (mean ± SD = 5.02 ± 3.62). Model 1 (Half-Normal) showed the best fit to the data. The estimated population size was 50 animals and the density was 0.32 individuals km-2. Density estimates evaluated in the sub-areas where franciscanas occurred resulted in a density of 0.46 individuals km-2. Monitoring this population is of considerable importance due to the constant threats that this species faces in this bay.

scholarly journals Vulture populations in Uganda: using road survey data to measure both densities and encounter rates within protected and unprotected areas

2014 ◽  
Vol 25 (4) ◽  
pp. 399-414 ◽  
Author(s):  
DEREK POMEROY ◽  
PHIL SHAW ◽  
MICHAEL OPIGE ◽  
GEORGE KAPHU ◽  
DARCY L. OGADA ◽  
...  
Keyword(s):  
Survey Data ◽  
Survey Methods ◽  
Distance Sampling ◽  
Population Estimates ◽  
Breeding Density ◽  
Density Estimates ◽  
Encounter Rates ◽  
Two Measures ◽  
Road Survey ◽  
Agricultural Areas

SummarySix out of seven vulture species whose global ranges lie largely or wholly within Africa are listed as globally threatened. Since their current distributions individually span up to 39 range states there is a pressing need to develop robust, standardised methods that provide a clear measure of range-wide changes in abundance. Yet, survey methods currently used tend to yield either of two measures: estimates of breeding density, derived mainly from nest counts; or linear encounter rates, derived from road surveys. Here, we present the results of a six-year survey of six vulture species in Uganda, in which we used road counts, in combination with Distance sampling, to determine both encounter rates and densities within protected areas (PAs), and in predominantly pastoral and agricultural areas. In combination, five scavenging species were detected 4–6 times more frequently in PAs than elsewhere, and two species, White-backed Vulture Gyps africanus and Lappet-faced Vulture Torgus tracheliotus, were recorded only within PAs. We estimate that PAs held c.1,300–3,900 individuals of the five scavenging species combined, including c.1,250–2,900 individuals of two Gyps species. We also present national population estimates for two species: White-backed Vulture (c.1,000–2,600 birds) and Lappet-faced Vulture (c.160–500 birds). Although sightings were assigned to only three broad distance bands, Distance sampling provided estimates with a level of precision similar to that achieved for linear encounter rates, but as density estimates; a form more readily comparable with results obtained from other survey types.

scholarly journals Planning and designing urban places in response to climate and local culture: A case study of Mussafah District in Abu Dhabi

Spatium ◽  
2011 ◽  
pp. 14-22 ◽  
Author(s):  
Milica Bajic-Brkovic ◽  
Mira Milakovic
Keyword(s):  
Urban Development ◽  
International Society ◽  
Urban Spaces ◽  
Abu Dhabi ◽  
Local Culture ◽  
Starting Point ◽  
The World ◽  
The Subject ◽  
Urban Places

This paper deals with how climate and local culture specifics contribute to urban diversity, and how they affect the way urban spaces are being conceived, planned and designed. The authors argue that regardless of the globally accepted principles of sustainability which emphasize smart responses, diversity and culture as the prime drives in urban development of, cities around the world are continually experiencing the all-alike solutions, which often compromise their identity and character. Having taken the genuine stands of the philosophy as a starting point for examining the subject, the authors explore and present how the climate specifics, along with the uniqueness of local culture, lead toward the solutions which make a difference to their cities. The discussion is illustrated by the case study the authors were engaged in, the Mussafah District project in Abu Dhabi, a redevelopment proposal recently initiated and developed by International Society of Urban and Regional Planners -ISOCARP and Urban Planning Council of Abu Dhabi.

Determining the distribution and abundance of a regional koala population in south-east Queensland for conservation management

2004 ◽  
Vol 31 (2) ◽  
pp. 109 ◽  
Author(s):  
David S. Dique ◽  
Harriet J. Preece ◽  
Jim Thompson ◽  
Deidré L. de Villiers
Keyword(s):  
Urban Development ◽  
Population Size ◽  
Tree Species ◽  
Urban Areas ◽  
Confidence Limit ◽  
Conservation Management ◽  
Density Estimates ◽  
Remnant Habitat ◽  
Effective Conservation

Koala surveys were used to determine the distribution and abundance of a threatened regional koala population in south-east Queensland to assist with the development of effective conservation management programs. Daytime systematic searches of strip transects were conducted twice yearly from 1996 to 1999 to determine koala density at a number of sites in urban, remnant bushland and bushland strata. Mean density estimates for 27 survey sites ranged from 0.02 to 1.26 koalas ha–1. Koala densities were generally higher in large tracts and remnant patches of eucalypt bushland towards the centre of the region with lower but significant densities in urban areas. Two estimates of population size were obtained: 7230 (±1668, 95% confidence limit) and 6246 (±1444, 95% confidence limit). The estimate of 6246 was considered to provide a better indication of actual population size as it reduced the variation within strata and took into account the distribution of koalas across the region. It is likely that determining habitat areas for conservation based on where koalas actually occur rather than identifying distributions of 'preferred' tree species or community reports, as has been promoted in other studies, is a better indicator of the conservation significance of remnant habitat areas. Future koala-management programs should ensure that the significance of eucalypt bushland areas towards the centre of the study area is not compromised by future urban development and associated threats to koalas.

Fact or fiction? A discussion on the subject of Hashimoto's Encephalopathy and presentation of a case study

2020 ◽  
Author(s):  
Jena Mamdani ◽  
Sarah Chatharoo ◽  
Pankaj Chaturvedi
Keyword(s):  
Hashimoto’S Encephalopathy ◽  
The Subject
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