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

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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Density and Abundance Estimation of Amazonian River Dolphins: Understanding Population Size Variability

Journal of Marine Science and Engineering ◽

10.3390/jmse9111184 ◽

2021 ◽

Vol 9 (11) ◽

pp. 1184

Author(s):

Mariana Paschoalini ◽

Fernando Trujillo ◽

Miriam Marmontel ◽

Federico Mosquera-Guerra ◽

Renan Lopes Paitach ◽

...

Keyword(s):

Population Size ◽

Amazon Basin ◽

Anthropogenic Activities ◽

Distance Sampling ◽

Inia Geoffrensis ◽

Size Variability ◽

Research Alliance ◽

Size Gradient ◽

Density Population ◽

Population Numbers

The dolphins Inia geoffrensis—boto and Sotalia fluviatilis—tucuxi are threatened cetaceans inhabiting river ecosystems in South America; population numbers are still lacking for many areas. This paper provides density and abundance estimations of boto and tucuxi in 15 rivers sampled during the past nine years as part of a multinational research alliance. Visual boat-survey data collection protocols and analyses have been developed since 2012 (based on Distance Sampling methods) and recently reviewed (2019) to improve robustness and comparability. Differences across the sampled rivers and the analyzed river basins (Amazon and Orinoco) pointed to a density/population size gradient with lower densities and abundances observed in the Orinoco basin (0.9–1.5 ind./km²), passing through the eastern Amazon basin (2–5 ind./km²), and the largest numbers found at the central Brazilian Amazon (lower Purus River—2012 (14.5 boto/km², N = 7672; 17.1 tucuxi/km², N = 9238)). However, in other parts of the central Amazon, the density of dolphins was smaller than expected for high productive whitewater rivers (1–1.7 ind./km² in the Japurá and Solimões rivers). We attributed these differences to specific features of the basin (e.g., hydro-geomorphology) as well as to the cumulative effects of anthropogenic activities.

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Range expansion, density and conservation of the Araucaria Tit-spinetail Leptasthenura setaria (Furnariidae) in Argentina: the role of araucaria Araucaria angustifolia (Araucariaceae) plantations

Bird Conservation International ◽

10.1017/s0959270907000871 ◽

2007 ◽

Vol 17 (4) ◽

pp. 341-349 ◽

Cited By ~ 5

Author(s):

Gustavo Sebastián Cabanne ◽

Gustavo Andrés Zurita ◽

Sergio Hugo Seipke ◽

María Isabel Bellocq

Keyword(s):

Population Size ◽

Conservation Status ◽

Distance Sampling ◽

Suitable Habitat ◽

Araucaria Angustifolia ◽

Fragmented Habitat ◽

North East ◽

Forestry Practices

AbstractThe Araucaria Tit-spinetail Leptasthenura setaria (Furnariidae) is a globally Near Threatened species. Its habitat, the araucaria (Araucaria angustifolia) rainforest of south-east Brazil and north-east Argentina, is highly fragmented and reduced to nearly 10% of its original range. The species has also been recorded in commercial araucaria plantations that comprise about 80% of its suitable habitat in Argentina. This situation provides an opportunity for the conservation of the Araucaria Tit-spinetail in a human-modified landscape. We assessed the occurrence of the species in the region and estimated its density and total population size in araucaria plantations in Argentina. We discuss the value of plantations in the conservation of the bird, and evaluate its conservation status in Argentina using IUCN criteria. The density of the tit-spinetail in araucaria plantations, estimated by a distance sampling method, was 9 birds ha−1. The overall population size in commercial plantations appears to be large (>7,000 birds), showing that araucaria plantations play an important role in the conservation of the bird. However, plantations must not replace the native araucaria forest because the former are an intrinsically fragmented habitat influenced primarily by economic factors and forestry practices. The long-term conservation and restoration of araucaria rainforest in Argentina and Brazil must be guaranteed to conserve the Araucaria Tit-spinetail and other species associated with this rainforest. Based on the restricted and very fragmented habitat, the Araucaria Tit-spinetail should be regarded as Vulnerable in Argentina.

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Predicting Impacts of Climate Change on Chinese Hybrid Poplar Using Maxent Modeling

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.651-653.1496 ◽

2014 ◽

Vol 651-653 ◽

pp. 1496-1503 ◽

Cited By ~ 2

Author(s):

Jin Song Dai ◽

Fu Liang Cao

Keyword(s):

Climate Change ◽

Hybrid Poplar ◽

Scientific Basis ◽

Suitable Habitat ◽

Maxent Model ◽

Habitat Area ◽

Maxent Modeling ◽

Auc Value ◽

Better Than ◽

Impacts Of Climate Change

Maximum entropy (Maxent) modeling was used to predict the potential climate habitat distribution of Chinese hybrid poplar (clone I-63, I-69 and I-72). Occurrence data were collected from literatures. The Maxent model performed better than random with an average cross-validated AUC value of 0.96. Under the three future climate scenarios (emission scenarios A1B, A2 and B1), the geographic distribution of suitable habitat would shift from southwest to northeast, the suitable habitat area of scenario A1B increased most compared to other two, the ranking of the loss habitat area was scenario B1 > scenario A2 > scenario A1B, and the gain habitat area was scenario A1B > scenario A2 > scenario B1. The results of this work could be used as scientific basis for adapting and mitigating Chinese hybrid poplar planting to a climate change.

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Capitoline Dolphins: Residency Patterns and Abundance Estimate of Tursiops truncatus at the Tiber River Estuary (Mediterranean Sea)

Biology ◽

10.3390/biology10040275 ◽

2021 ◽

Vol 10 (4) ◽

pp. 275

Author(s):

Daniela Silvia Pace ◽

Chiara Di Marco ◽

Giancarlo Giacomini ◽

Sara Ferri ◽

Margherita Silvestri ◽

...

Keyword(s):

Population Size ◽

Tursiops Truncatus ◽

Site Fidelity ◽

Bottlenose Dolphins ◽

River Estuary ◽

Suitable Habitat ◽

Tyrrhenian Sea ◽

Abundance Estimate ◽

Photo Identification ◽

Tiber River

Periodic assessments of population status and trends to detect natural influences and human effects on coastal dolphin are often limited by lack of baseline information. Here, we investigated for the first time the site-fidelity patterns and estimated the population size of bottlenose dolphins (Tursiops truncatus) at the Tiber River estuary (central Mediterranean, Tyrrhenian Sea, Rome, Italy) between 2017 and 2020. We used photo-identification data and site-fidelity metrics to study the tendency of dolphins to remain in, or return to, the study area, and capture–recapture models to estimate the population abundance. In all, 347 unique individuals were identified. The hierarchical cluster analysis highlighted 3 clusters, labeled resident (individuals encountered at least five times, in three different months, over three distinct years; n = 42), part-time (individuals encountered at least on two occasions in a month, in at least two different years; n = 73), and transient (individuals encountered on more than one occasion, in more than 1 month, none of them in more than 1 year; n = 232), each characterized by site-fidelity metrics. Open POPAN modeling estimated a population size of 529 individuals (95% CI: 456–614), showing that the Capitoline (Roman) coastal area and nearby regions surrounding the Tiber River estuary represent an important, suitable habitat for bottlenose dolphins, despite their proximity to one of the major urban centers in the world (the city of Rome). Given the high number of individuals in the area and the presence of resident individuals with strong site fidelity, we suggest that conservation plans should not be focused only close to the Tiber River mouths but extended to cover a broader scale of area.

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Evaluating Alternative Flight Plans in Thermal Drone Wildlife Surveys—Simulation Study

Remote Sensing ◽

10.3390/rs13061102 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1102

Author(s):

Julia Witczuk ◽

Stanisław Pagacz

Keyword(s):

Computer Simulations ◽

Survey Design ◽

Distance Sampling ◽

Line Of Sight ◽

Density Estimates ◽

Accuracy And Precision ◽

Survey Costs ◽

Random Survey ◽

Density Population

The rapidly developing technology of unmanned aerial vehicles (drones) extends to the availability of aerial surveys for wildlife research and management. However, regulations limiting drone operations to visual line of sight (VLOS) seriously affect the design of surveys, as flight paths must be concentrated within small sampling blocks. Such a design is inferior to spatially unrestricted randomized designs available if operations beyond visual line of sight (BVLOS) are allowed. We used computer simulations to assess whether the VLOS rule affects the accuracy and precision of wildlife density estimates derived from drone collected data. We tested two alternative flight plans (VLOS vs. BVLOS) in simulated surveys of low-, medium- and high-density populations of a hypothetical ungulate species with three levels of effort (one to three repetitions). The population density was estimated using the ratio estimate and distance sampling method. The observed differences in the accuracy and precision of estimates from the VLOS and BVLOS surveys were relatively small and negligible. Only in the case of the low-density population (2 ind./100 ha) surveyed once was the VLOS design inferior to BVLOS, delivering biased and less precise estimates. These results show that while the VLOS regulations complicate survey logistics and interfere with random survey design, the quality of derived estimates does not have to be compromised. We advise testing alternative survey variants with the aid of computer simulations to achieve reliable estimates while minimizing survey costs.

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Distribution, ecology and conservation of an endangered Andean hummingbird: the Violet-throated Metaltail (Metallura baroni)

Bird Conservation International ◽

10.1017/s0959270908007703 ◽

2009 ◽

Vol 19 (1) ◽

pp. 63-76 ◽

Cited By ~ 48

Author(s):

BORIS A. TINOCO ◽

PEDRO X. ASTUDILLO ◽

STEVEN C. LATTA ◽

CATHERINE H. GRAHAM

Keyword(s):

Suitable Habitat ◽

Species Occurrence ◽

Entropy Model ◽

Maxent Model ◽

The North ◽

The Andes ◽

Guide Field ◽

South Central ◽

Detailed Assessment ◽

Endangered Status

SummaryThe Violet-throated MetaltailMetallura baroniis a high altitude hummingbird endemic to south-central Ecuador currently considered globally ‘Endangered’. Here we present the first detailed assessment of its distribution, ecology and conservation. We first used a maximum entropy model (Maxent model) to create a predicted distribution for this species based on very limited species occurrence data. We used this model to guide field surveys for the species between April and October 2006. We found a positive relationship between model values and species presence, indicating that the model was a useful tool to predict species occurrence and guide exploration. In the sites where the metaltail was found we gathered data on its habitat requirements, food resources and behaviour. Our results indicate that Violet-throated Metaltail is restricted to the Western Cordillera of the Andes Mountains in Azuay and Cañar provinces of Ecuador, with an area of extent of less than 2,000 km2. Deep river canyons to the north and south, lack of suitable habitat, and potential interspecific competition in the east may limit the bird's distribution. The species occurred in three distinct habitats, includingPolylepiswoodland, the upper edge of the montane forest, and in shrubby paramo, but we found no difference in relative abundance among these habitats. The metaltail seems to tolerate moderate human intervention in its habitats as long as some native brushy cover is maintained. We found thatBrachyotumsp.,Berberissp., andBarnadesiasp. were important nectar resources. The ‘Endangered’ status of this species is supported due to its restricted distribution in fragmented habitats which are under increasing human pressures.

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

Wildlife Research ◽

10.1071/wr10234 ◽

2011 ◽

Vol 38 (3) ◽

pp. 221 ◽

Cited By ~ 6

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.

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Habitat associations and conservation status of an endemic forest dwarf chameleon (Bradypodion sp.) from South Africa

Oryx ◽

10.1017/s0030605306000408 ◽

2006 ◽

Vol 40 (2) ◽

pp. 183-188 ◽

Cited By ~ 6

Author(s):

Walter J. Reisinger ◽

Devi M. Stuart-Fox ◽

Barend F.N. Erasmus

Keyword(s):

South Africa ◽

Conservation Status ◽

Canopy Cover ◽

Iucn Red List ◽

Habitat Associations ◽

Suitable Habitat ◽

Area Of Occupancy ◽

Forest Interior ◽

Forest Remnants ◽

Iucn Red List Criteria

We quantified habitat associations and evaluated the conservation status of a recently identified, undescribed species of dwarf chameleon, Bradypodion sp. nov. Dhlinza, endemic to scarp forest remnants in KwaZulu-Natal Province, South Africa. At the microhabitat scale the Dhlinza dwarf chameleon was found more often in forest gaps and near paths than highly disturbed edges or forest interior. Chameleon presence was not explained by forest physiognomic variables such as vine cover, shrub and tree density, or canopy cover. Presence near gaps may be better explained by the combined effects of the thermal microenvironment and food availability. The species is moderately common where it occurs, with estimated densities of 4.7, 8.7 and 29.7 individuals per ha within forest interior, edges and gaps respectively. At the landscape scale, the chameleon occurs only in three remnant forests: the Dhlinza, Entumeni and Ongoye Forests. The species' extent of occurrence was estimated to be 88 km2 and its area of occupancy 49 km2. Based on the small area of remaining suitable habitat, this species meets the requirements for categorization as Endangered according to IUCN Red List criteria.

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Floristic composition of the Montane Forest in the Almadina-Barro Preto axis, Southern Bahia, Brazil

Biota Neotropica ◽

10.1590/s1676-06033878 ◽

2014 ◽

Vol 14 (1) ◽

Cited By ~ 9

Author(s):

Macielle Macedo Coelho ◽

André Márcio Amorim

Keyword(s):

Species Richness ◽

Tropical Forests ◽

Atlantic Forest ◽

Floristic Composition ◽

Woody Species ◽

Life Forms ◽

Montane Forest ◽

Forest Remnants ◽

Southern Bahia ◽

Arboreal Habit

The aim of this study is to survey the angiosperms of two montane forest remnants in the southern Bahia, Brazil: Corcovado (SCO) and Pedra Lascada (SPL). Both fragments are located in the municipality of Almadina and Barro Preto, respectively, and are 18 km distant from each other. We sampled 899 species of angiosperms distributed in 437 genera and 116 families. The SCO was the richest area with 678 species, distributed in 367 genera and 100 families. SPL showed 466 species in 269 genera and 88 families. The percentage of species identified was 85.8% and of this total, 37.7% are endemic to the Atlantic Forest, 11.2% are endemic to southern Bahia and northern Espírito Santo and 7% are disjunct between the Atlantic Forest and Amazon. The remaining percentages (44.3%) were of species widely distributed. The richest families in the two areas were Orchidaceae (10%), Rubiaceae (7%), Bromeliaceae (5.5%), Melastomataceae (4.2%) and Poaceae (4%). The richest genera were Psychotria (2%),Piper (1.8%), Ocotea (1.6%),Vriesea (1.5%) and Peperomia (1.4%). More than half of the recorded species showed non-arboreal habit, regarding life forms documented. That comes against the assertion that many authors in the tropical forests, where species richness in angiosperms is expected for non-woody species, especially in montane forests. Twelve species have been identified as new, but seven others already described from collections previously obtained in these two areas. Orchidaceae, Rubiaceae, Poaceae and Bromeliaceae showed significant richness in this study these families are commonly reported as the richest in other inventories in the Atlantic Forest in southern Bahia reinforcing their importance to the regional flora. The high levels of richness, endemism, and the growing numbers of new taxonomic discoveries from the SPL and SCO sites indicate the biological importance of these two forest remnants. The implementation of parks or other protected environmental reserves would be essential to the conservation of its species.

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Global distribution of soapberries (Sapindus L.) habitats under current and future climate scenarios

Scientific Reports ◽

10.1038/s41598-021-98389-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jiming Liu ◽

Lianchun Wang ◽

Caowen Sun ◽

Benye Xi ◽

Doudou Li ◽

...

Keyword(s):

Large Scale ◽

Global Climate ◽

Future Climate ◽

Environmental Data ◽

Climate Projections ◽

Suitable Habitat ◽

Maxent Model ◽

Mean Temperature ◽

Suitable Habitats ◽

Large Scale Cultivation

AbstractSapindus (Sapindus L.) is a widely distributed economically important tree genus that provides biodiesel, biomedical and biochemical products. However, with climate change, deforestation, and economic development, the diversity of Sapindus germplasms may face the risk of destruction. Therefore, utilising historical environmental data and future climate projections from the BCC-CSM2-MR global climate database, we simulated the current and future global distributions of suitable habitats for Sapindus using a Maximum Entropy (MaxEnt) model. The estimated ecological thresholds for critical environmental factors were: a minimum temperature of 0–20 °C in the coldest month, soil moisture levels of 40–140 mm, a mean temperature of 2–25 °C in the driest quarter, a mean temperature of 19–28 °C in the wettest quarter, and a soil pH of 5.6–7.6. The total suitable habitat area was 6059.97 × 104 km2, which was unevenly distributed across six continents. As greenhouse gas emissions increased over time, the area of suitable habitats contracted in lower latitudes and expanded in higher latitudes. Consequently, surveys and conservation should be prioritised in southern hemisphere areas which are in danger of becoming unsuitable. In contrast, other areas in northern and central America, China, and India can be used for conservation and large-scale cultivation in the future.

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