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 Out of the darkness: the first comprehensive survey of the Critically Endangered Anjouan Scops Owl Otus capnodes

2014 ◽  
Vol 25 (3) ◽  
pp. 322-334 ◽  
Author(s):  
KATHLEEN E. GREEN ◽  
BRONWEN M. DANIEL ◽  
SAMUEL P. LLOYD ◽  
ISHAKA SAID ◽  
AMELAID HOUMADI ◽  
...  
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Distance Sampling ◽  
Bird Species ◽  
Iucn Red List ◽  
Critically Endangered ◽  
Encounter Rate ◽  
Wet Season ◽  
Point Counts ◽  
Comprehensive Survey

SummaryAlthough birds are among the best studied taxa, many of the globally threatened species lack the information required to fully assess their conservation status and needs. One such species is the Anjouan Scops Owl Otus capnodes which was presumed extinct until its rediscovery to science in 1992. Based on the limited extent and decline of the moist forests in the highlands of Anjouan in the Comoro Islands, a population size of only 100–200 pairs was estimated and the species was classified as ‘Critically Endangered’. The current study is the first comprehensive survey ever conducted on this species, and aimed to establish the current distribution and population size. Point counts with distance sampling were conducted across the agroforestry and forest zones of Anjouan in both a dry and wet season. A niche suitability model predicted the species distribution to be wider than expected with owls observed as low as 300 m altitude and in highly modified agroforestry habitats. However, the encounter rate in natural relatively undisturbed forest was significantly greater than in other habitats. The wider than expected geographic range of O. capnodes supports a possible downlisting of this species on the IUCN Red List to ‘Endangered’. Population size was found to be far greater than previously thought, at approximately 3,450 individual owls in the dry season and 5,450 in the wet season. These results show the importance of investing in robust surveys of poorly known and cryptic bird species, and provide up to date and important information for landscape scale conservation planning in the Comoros Islands.

scholarly journals Status assessment of the Critically Endangered Azores Bullfinch Pyrrhula murina

2011 ◽  
Vol 21 (4) ◽  
pp. 477-489 ◽  
Author(s):  
RICARDO S. CEIA ◽  
JAIME A. RAMOS ◽  
RUBEN H. HELENO ◽  
GEOFF M. HILTON ◽  
TIAGO A. MARQUES
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Distance Sampling ◽  
Iucn Red List ◽  
Range Size ◽  
Critically Endangered ◽  
Survey Method ◽  
Mountain Range ◽  
Laurel Forest ◽  
Area Of Occupancy

SummaryThe Azores Bullfinch is endemic to the island of São Miguel (Azores, Portugal). Its status was uplisted to Critically Endangered in 2005 on the basis of an extremely small and declining population that was considered to be restricted to a very small mountain range (43 km2), in a single location, within which the spread of invasive plants constituted a threat to habitat quality. Nevertheless, information was mostly inferred, or the product of, non-systematic studies. In order to carry out a complete assessment of the conservation status we analysed: (i) population trend, calculated from annual monitoring 1991–2008, (ii) population size, and (iii) range size, obtaining estimates in a single morning study in 2008 involving the simultaneous participation of 48 observers. Contrary to previous inferences, the population is no longer decreasing, although quality of laurel forest habitat continues to decline due to the persistent threat of invasive species. Population size (mean ± SE) was estimated at 1,064 ± 304 individuals using distance sampling methods, although the estimate was very sensitive to the survey method used. Range size estimates (extent of occurrence and area of occupancy) were 144 km2 and 83 km2 respectively. Given the present information, we propose the downlisting of Azores Bullfinch to Endangered on the IUCN Red List.

scholarly journals Status and distribution of the endemic Bali starling Leucopsar rothschildi

Oryx ◽  
2000 ◽  
Vol 34 (3) ◽  
pp. 188-197 ◽  
Author(s):  
S. (Bas) van Balen ◽  
I Wayan A. Dirgayusa ◽  
I Made W. Adi Putra ◽  
Herbert H. T. Prins
Keyword(s):  
Population Size ◽  
Small Area ◽  
Small Population ◽  
Critically Endangered ◽  
Suitable Habitat ◽  
Pet Trade ◽  
Monsoon Forest ◽  
Habitat Conversion ◽  
Natural Range ◽  
Precarious Situation

AbstractThe Bali starling Leucopsar rothschildi is a passerine endemic to the dry monsoon forest of the island of Bali, Indonesia. Habitat conversion and excessive capture for the pet trade brought the species to the verge of extinction in the 1980s. The species is critically endangered because of 1) an extremely small population size, 2) restriction to a small area, 3) illegal trapping, and 4) diminishing suitable habitat left within its natural range. An intricate web of factors prevents the Bali starling from emerging from this precarious situation.

scholarly journals Population estimates and habitat use by the Critically Endangered Taita Apalis Apalis fuscigularis in south-eastern Kenya

2010 ◽  
Vol 20 (4) ◽  
pp. 440-455 ◽  
Author(s):  
LUCA BORGHESIO ◽  
DAINA SAMBA ◽  
MWANGI GITHIRU ◽  
LEON BENNUN ◽  
KEN NORRIS
Keyword(s):  
Habitat Use ◽  
Population Size ◽  
Habitat Structure ◽  
Predictive Power ◽  
Total Population ◽  
Distance Sampling ◽  
Critically Endangered ◽  
South Eastern ◽  
Forest Sites ◽  
Global Population

SummaryThe Taita Apalis Apalis fuscigularis (IUCN category: Critically Endangered) is a species endemic to south-eastern Kenya. We assessed population size and habitat use in the three forest sites in which it is known to occur (Ngangao, Chawia and Vuria, totalling 257 ha). The estimate of total population size, derived from distance sampling at 412 sample points, ranged from 310 to 654 individuals, with the northern section of Ngangao fragment having 10-fold higher densities than Chawia (2.47–4.93 versus 0.22–0.41 birds ha−1). Ngangao north alone hosted 50% of the global population of the species. The highly degraded Vuria fragment also had moderately high densities (1.63–3.72 birds ha−1) suggesting that the species tolerates some human disturbance. Taita Apalis prefers vegetation with abundant climbers, but the predictive power of habitat use models was low, suggesting that habitat structure is not a primary cause for the low density of the species in Chawia. Protecting the subpopulation in the northern section of Ngangao is a priority, as is identifying factors responsible of the low abundance in Chawia, because ameliorating conditions in this large fragment could substantially increase the population of Taita Apalis.

The importance of survey design in distance sampling: field evaluation using domestic sheep

2011 ◽  
Vol 38 (3) ◽  
pp. 221 ◽  
Author(s):  
Tom A. Porteus ◽  
Suzanne M. Richardson ◽  
Jonathan C. Reynolds
Keyword(s):  
Population Size ◽  
Survey Design ◽  
Distance Sampling ◽  
Field Evaluation ◽  
Stage I ◽  
Stage Ii ◽  
Line Transect ◽  
Domestic Sheep ◽  
Management Decisions ◽  
Mobile Species

Context Sampling methods to estimate animal density require good survey design to ensure assumptions are met and sampling is representative of the survey area. Management decisions are often made based on these estimates. However, without knowledge of true population size it is not possible for wildlife biologists to evaluate how biased the estimates can be if survey design is compromised. Aims Our aims were to use distance sampling to estimate population size for domestic sheep free-ranging within large enclosed areas of hill country and, by comparing estimates against actual numbers, examine how bias and precision are impaired when survey design is compromised. Methods We used both line and point transect sampling to derive estimates of density for sheep on four farms in upland England. In Stage I we used limited effort and different transect types to compromise survey design. In Stage II we increased effort in an attempt to improve on the Stage I estimates. We also examined the influence of a walking observer on sheep behaviour to assess compliance with distance sampling assumptions and to improve the fit of models to the data. Key results Our results show that distance sampling can lead to biased and imprecise density estimates if survey design is poor, particularly when sampling high density and mobile species that respond to observer presence. In Stage I, walked line transects were least biased; point transects were most biased. Increased effort in Stage II reduced the bias in walked line transect estimates. For all estimates, the actual density was within the derived 95% confidence intervals, but some of these spanned a range of over 100 sheep per km2. Conclusions Using a population of known size, we showed that survey design is vitally important in achieving unbiased and precise density estimation using distance sampling. Adequate transect replication reduced the bias considerably within a compromised survey design. Implications Management decisions based on poorly designed surveys must be made with an appropriate understanding of estimate uncertainty. Failure to do this may lead to ineffective management.

scholarly journals Distribution and habitat associations of the Critically Endangered frog Walkerana phrynoderma (Anura: Ranixalidae), with an assessment of potential threats, abundance, and morphology

2018 ◽  
Vol 17 (1) ◽  
pp. 21
Author(s):  
Arun Kanagavel ◽  
Sethu Parvathy ◽  
Abhiijth P. Chundakatil ◽  
Neelesh Dahanukar ◽  
Benjamin Tapley
Keyword(s):  
Western Ghats ◽  
Tamil Nadu ◽  
Habitat Associations ◽  
Critically Endangered ◽  
Suitable Habitat ◽  
Time Activity ◽  
Western Ghats Of India ◽  
Pesticide Runoff ◽  
The Impact ◽  
The Western Ghats

Distribution and habitat associations of the Critically Endangered frog Walkerana phrynoderma (Anura: Ranixalidae), with an assessment of potential threats, abundance, and morphology. Little is known about Walkerana phrynoderma, a frog endemic to the Anamalai Hills of the Western Ghats of India. Baseline information (i.e., distribution, threats, habitat characteristics, activity patterns, and relative abundance) is provided for this species, with the aim of improving our understanding of the status of the species in the wild. Visual-encounter, transect, and time-activity budget surveys were conducted in and around the Anamalai Hills of the Western Ghats. The frog skin was swabbed to determine the presence/absence of Batrachochytrium dendrobatidis, and habitat and environmental characteristics were recorded at sites where W. phrynoderma was found. These data were compared with those of sites apparently lacking this species that had suitable habitat. Walkerana phrynoderma is restricted to evergreen forests between 1300 and 1700 m a.s.l. in the Anamalai Tiger Reserve and at Munnar; thus, its range was extended from the state of Tamil Nadu to the adjoining state of Kerala. Pesticide runoff and human disturbance are the most severe threats to the species; B. dendrobatidis was not detected. This nocturnal anuran prefers forest edges and is associated with well-shaded forest foors in cool areas near freshwater streams. Walkerana phrynoderma is rarely encountered whereas its congener, W. leptodactyla, is more common. The impact of anthropogenic disturbances, especially waste disposal and development of tourism infrastructure, should be evaluated. The land that is owned by the Forest Department peripheral to the protected areas could be designated as eco-sensitive sites to prevent changes in land use that could have an adverse effect on W. phrynoderma.

scholarly journals Macroeconomic Impacts of Climate Change Driven by Changes in Crop Yields

2018 ◽  
Vol 10 (10) ◽  
pp. 3673 ◽  
Author(s):  
Shinichiro Fujimori ◽  
Toshichika Iizumi ◽  
Tomoko Hasegawa ◽  
Jun’ya Takakura ◽  
Kiyoshi Takahashi ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Population Size ◽  
Large Population ◽  
Food Prices ◽  
Production Volume ◽  
Total Uncertainty ◽  
Indicator Value ◽  
Macroeconomic Impacts ◽  
Macroeconomic Indicator

Changes in agricultural yields due to climate change will affect land use, agricultural production volume, and food prices as well as macroeconomic indicators, such as GDP, which is important as it enables one to compare climate change impacts across multiple sectors. This study considered five key uncertainty factors and estimated macroeconomic impacts due to crop yield changes using a novel integrated assessment framework. The five factors are (1) land-use change (or yield aggregation method based on spatially explicit information), (2) the amplitude of the CO2 fertilization effect, (3) the use of different climate models, (4) socioeconomic assumptions and (5) the level of mitigation stringency. We found that their global impacts on the macroeconomic indicator value were 0.02–0.06% of GDP in 2100. However, the impacts on the agricultural sector varied greatly by socioeconomic assumption. The relative contributions of these factors to the total uncertainty in the projected macroeconomic indicator value were greater in a pessimistic world scenario characterized by a large population size, low income, and low yield development than in an optimistic scenario characterized by a small population size, high income, and high yield development (0.00%).

Global population size of a critically endangered lemur, Perrier's sifaka

2007 ◽  
Vol 10 (2) ◽  
pp. 254-262 ◽  
Author(s):  
M. A. Banks ◽  
E. R. Ellis ◽  
Antonio ◽  
P. C. Wright
Keyword(s):  
Population Size ◽  
Critically Endangered ◽  
Global Population

scholarly journals Estimated Density, Population Size and Distribution of the Endangered Western Hoolock Gibbon (Hoolock hoolock) in Forest Remnants in Bangladesh

Diversity ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 490
Author(s):  
Habibon Naher ◽  
Hassan Al-Razi ◽  
Tanvir Ahmed ◽  
Sabit Hasan ◽  
Areej Jaradat ◽  
...  
Keyword(s):  
Population Size ◽  
Tropical Forests ◽  
Forest Regeneration ◽  
Distance Sampling ◽  
Suitable Habitat ◽  
Careful Evaluation ◽  
Maxent Model ◽  
Maxent Modeling ◽  
Forest Remnants ◽  
Density Population

Tropical forests are threatened worldwide due to deforestation. In South and Southeast Asia, gibbons (Hylobatidae) are important to seed dispersal and forest regeneration. Most gibbons are threatened due to deforestation. We studied the western hoolock gibbon (Hoolock hoolock) in Bangladesh to determine population size and extent of suitable habitat. We used distance sampling to estimate density across 22 sites in northeastern and southeastern Bangladesh. We used Maxent modeling to determine areas of highly suitable habitat throughout Bangladesh. Density was estimated to be 0.39 ± 0.09groups/km2, and the total estimated population was 468.96 ± 45.56 individuals in 135.31 ± 2.23 groups. The Maxent model accurately predicted gibbon distribution. Vegetation cover, isothermality, annual precipitation, elevation and mean temperature of the warmest quarter influenced distribution. Two areas in the northeast and two areas in the southeast have high potential for gibbon conservation in Bangladesh. We also found significantly more gibbons in areas that had some level of official protection. Thus, we suggest careful evaluation, comprehensive surveys and restoration of habitats identified as suitable for gibbons. We recommend bringing specific sites in the northeastern and southeastern regions under protection to secure habitat for remaining gibbon populations.

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