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Integrating occurrence and detectability patterns based on interview data: a case study for threatened mammals in Equatorial Guinea.

ABSTRACT: Occurrence models that account for imperfect detection of species are increasingly used for estimating geographical range, for determining species-landscape relations and to prioritize conservation actions worldwide. In 2010, we conducted a large-scale survey in Río Muni, the mainland territory of Equatorial Guinea, which aimed to estimate the probabilities of occurrence and detection of threatened mammals based on environmental covariates, and to identify priority areas for conservation. Interviews with hunters were designed to record presence/absence data of seven species (golden cat, leopard, forest elephant, forest buffalo, western gorilla, chimpanzee and mandrill) in 225 sites throughout the region. We fitted single season occupancy models and recently developed models which also include false positive errors (i.e. species detected in places where it actually does not occur), which should provide more accurate estimates for most species, which are susceptible to mis-identification. Golden cat and leopard had the lowest occurrence rates in the region, whereas primates had the highest rates. All species, except gorilla, were affected negatively by human settlements. The southern half of Río Muni showed the highest occurrence of the species studied, and conservation strategies for ensuring the persistence of threatened mammals should be focused on this area.

SUBMITTER: Martinez-Marti C

PROVIDER: S-EPMC5036030 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Integrating occurrence and detectability patterns based on interview data: a case study for threatened mammals in Equatorial Guinea.

Martínez-Martí Chele C Jiménez-Franco María V MV Royle J Andrew JA Palazón José A JA Calvo José F JF

Scientific reports 20160926

Occurrence models that account for imperfect detection of species are increasingly used for estimating geographical range, for determining species-landscape relations and to prioritize conservation actions worldwide. In 2010, we conducted a large-scale survey in Río Muni, the mainland territory of Equatorial Guinea, which aimed to estimate the probabilities of occurrence and detection of threatened mammals based on environmental covariates, and to identify priority areas for conservation. Interv ...[more]

PMID: 27666671

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Project description:BackgroundGeospatial datasets of population are becoming more common in models used for health policy. Publicly-available maps of human population make a consistent picture from inconsistent census data, and the techniques they use to impute data makes each population map unique. Each mapping model explains its methods, but it can be difficult to know which map is appropriate for which policy work. High quality census datasets, where available, are a unique opportunity to characterize maps by comparing them with truth.MethodsWe use census data from a bed-net mass-distribution campaign on Bioko Island, Equatorial Guinea, conducted by the Bioko Island Malaria Elimination Program as a gold standard to evaluate LandScan (LS), WorldPop Constrained (WP-C) and WorldPop Unconstrained (WP-U), Gridded Population of the World (GPW), and the High-Resolution Settlement Layer (HRSL). Each layer is compared to the gold-standard using statistical measures to evaluate distribution, error, and bias. We investigated how map choice affects burden estimates from a malaria prevalence model.ResultsSpecific population layers were able to match the gold-standard distribution at different population densities. LandScan was able to most accurately capture highly urban distribution, HRSL and WP-C matched best at all other lower population densities. GPW and WP-U performed poorly everywhere. Correctly capturing empty pixels is key, and smaller pixel sizes (100 m vs 1 km) improve this. Normalizing areas based on known district populations increased performance. The use of differing population layers in a malaria model showed a disparity in results around transition points between endemicity levels.DiscussionThe metrics in this paper, some of them novel in this context, characterize how these population maps differ from the gold standard census and from each other. We show that the metrics help understand the performance of a population map within a malaria model. The closest match to the census data would combine LandScan within urban areas and the HRSL for rural areas. Researchers should prefer particular maps if health calculations have a strong dependency on knowing where people are not, or if it is important to categorize variation in density within a city.

Project description:Hunting is one of the main driving forces behind large mammal density distribution in many regions of the world. In tropical Africa, urban demand for bushmeat has been shown to dominate over subsistence hunting and its impact often overrides spatial-ecological species characteristics. To effectively protect remaining mammal populations the main factors that influence their distribution need to be integrated into conservation area prioritisation and management plans. This information has been lacking for Río Muni, Equatorial Guinea, as prior studies have been outdated or have not systematically covered the continental region of the country. In this study we evaluated: 1) the relative importance of local vs. commercial hunting; 2) wildlife density of protected vs. non-protected areas; and 3) the importance of ecological factors vs. human influence in driving mammal density distribution in Río Muni. We adopted a systematic countrywide line transect approach with particular focus on apes and elephants, but also including other mammal species. For analysis of field data we used generalised linear models with a set of predictor variables representing ecological conditions, anthropogenic pressure and protected areas. We estimate that there are currently 884 (437-1,789) elephants and 11,097 (8,719-13,592) chimpanzees and gorillas remaining in Río Muni. The results indicate strong hunting pressures on both local and commercial levels, with roads demonstrating a negative impact on elephants and overall mammal body mass. Protected areas played no role in determining any of the mammal species distributions and significant human hunting signs were found inside these protected areas, illustrating the lack of environmental law enforcement throughout the country. Río Muni is currently under-represented in conservation efforts in Western Equatorial Africa, and we recommend a focus on cross-boundary conservation, in particular in the Monte Alén-Monts de Cristal and Río Campo Ma'an conservation landscapes, where the highest densities and diversity of large mammals remain.

Project description:Tuberculosis remains one of the major causes of morbidity and mortality in Equatorial Guinea, with an estimated incidence of 280 per 100,000 inhabitants, an estimated mortality rate of 96 per 100,000 inhabitants, and a treatment non-adherence rate of 21.4%. This study aimed to identify the factors associated to TB-related knowledge, attitudes, and stigma in order to design community intervention strategies that could improve TB diagnostic and treatment adherence in Equatorial Guinea. A nationwide cross-sectional survey of 770 household caregivers was conducted in Equatorial Guinea about TB knowledge, attitudes, and practices. Knowledge, attitude, and stigma scores were calculated through correct answers and the median was used as cut-off. Associated factors were analyzed calculating prevalence ratio (PR) and a 95% confidence interval (95% CI) through Poisson regression with robust variance. The percentage of women was 53.0% and median age was 46 years (IQR: 33-60). The percentage of caregivers with high TB related knowledge was 34.9%, with a bad attitude (52.5%) and low stigma (40.4%). A greater probability of having good knowledge was observed in those 45 years old or less (PR: 1.3, 95% CI: 1.1-1.6), those with higher education level (PR: 1.4, 95% CI: 1.1-1.8) and higher wealth (PR: 1.4, 95% CI: 1.0-2.0), while sex (PR = 0.8, 95% CI: 0.6-0.9), religion (PR = 1.4, 95% CI: 1.0-1.8), and good knowledge (PR = 1.4, 95% CI: 1.2-1.7) were associated with good attitudes. Wage employment (PR = 95% CI: 1.2-1.4), feeling well informed (PR = 0.7, 95% CI: 0.6-0.8), having good TB knowledge (PR = 1.3, 95% CI: 1.1-1.7), and some sources of information were associated with having lower TB-related stigma. This study found that a high percentage of caregivers in Equatorial Guinea lack important knowledge about TB disease and have bad attitudes and high TB-related stigma. Given the epidemiological situation of TB in the country, it is urgent to improve TB knowledge and awareness among Equatorial Guinea's general population.

Project description:BackgroundA successful malaria control programme began in 2004 on Bioko Island, Equatorial Guinea. From 2007, the same multiple malaria interventions, though reduced in scope for funding reasons, were introduced to the four mainland provinces of Equatorial Guinea (the continental region) aiming to recreate Bioko's success. Two provinces received long-lasting insecticidal nets (LLINs) and two provinces received biannual indoor residual spraying (IRS). Enhanced case management and communications were introduced throughout.MethodsEstimates of intervention coverage and indicators of malaria transmission for 2007 to 2011 were derived from annual malaria indicator surveys (MIS). Results were complemented by health information system (HIS) and entomological data. The personal protection offered by LLINs and IRS against Plasmodium falciparum infection was estimated with logistic regression.ResultsThe estimated proportion of children aged 1-4 using either an LLIN the previous night or living in a house sprayed in the last six months was 23% in 2007 and 42% in 2011. The estimated prevalence of P. falciparum in children aged 1-4 was 68% (N=1,770; 95% confidence interval [CI]: 58-76%) in 2007 and 52% (N=1,602; 95% CI: 44-61%) in 2011. Children 1-4 years had lower prevalence if they used an LLIN the previous night (N=1,124, 56%; adjusted odds ratio [aOR] 0.64, 95% CI: 0.55-0.74) or if they lived in a sprayed house (N=1,150, 57%; aOR 0.80, 95% CI: 0.62-1.03) compared to children with neither intervention (N=4,131, 66%, reference group). The minority of children who both used an LLIN and lived in a sprayed house had the lowest prevalence of infection (N=171, 45%; aOR 0.52, 95% CI: 0.35-0.78). High site-level intervention coverage did not always correlate with lower site-level P. falciparum prevalence. The malaria season peaked in either June or July, not necessarily coinciding with MIS data collection.ConclusionsThough moderate impact was achieved after five years of vector control, case management, and communications, prevalence remained high due to an inability to sufficiently scale-up coverage with either IRS or LLINs. Both LLINs and IRS provided individual protection, but greater protection was afforded to children who benefitted from both.

Dataset Information

Integrating occurrence and detectability patterns based on interview data: a case study for threatened mammals in Equatorial Guinea.

Publications

Integrating occurrence and detectability patterns based on interview data: a case study for threatened mammals in Equatorial Guinea.

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