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

View Article: PubMed Central - PubMed

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.

No MeSH data available.


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Estimated probabilities of occurrence for threatened mammals in Río Muni (Equatorial Guinea).All scales are occurrence probability per 25-km2 grid cell, calculated with the model averaging technique considering the most important models for each species showed in Supplementary Table S2. UTM coordinates are in zone 32N. Background maps in this figure have been generated by the authors using R version 3.2.5 (https://www.R-project.org/), and they have been incorporated in the corresponding panel using GIMP version 2.8.14 (https://www.gimp.org/). Outline maps of Africa and Equatorial Guinea has been drawn in R version 3.2.5 (https://www.R-project.org/) by using the maps and mapdata libraries (https://cran.r-project.org/web/packages/). Panels have been assembled with GIMP version 2.8.14 (https://www.gimp.org/).
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f1: Estimated probabilities of occurrence for threatened mammals in Río Muni (Equatorial Guinea).All scales are occurrence probability per 25-km2 grid cell, calculated with the model averaging technique considering the most important models for each species showed in Supplementary Table S2. UTM coordinates are in zone 32N. Background maps in this figure have been generated by the authors using R version 3.2.5 (https://www.R-project.org/), and they have been incorporated in the corresponding panel using GIMP version 2.8.14 (https://www.gimp.org/). Outline maps of Africa and Equatorial Guinea has been drawn in R version 3.2.5 (https://www.R-project.org/) by using the maps and mapdata libraries (https://cran.r-project.org/web/packages/). Panels have been assembled with GIMP version 2.8.14 (https://www.gimp.org/).

Mentions: Using the model averaging technique with top models for each species, we calculated average probabilities of occupancy and detection (Table 2) and developed corresponding occurrence maps for each species (Fig. 1). For most species, the average of the estimated probabilities of occupancy () was lower than the naïve estimate (i.e. observed proportion of occupied sites). The model-averaged estimates of the probabilities of occurrence () and detection () in all the cells of Río Muni region are shown in Table 2. Felids had restricted ranges ( = 0.19 for golden cat and  = 0.35 for leopard), especially golden cat throughout the area (Fig. 1a) and leopard in the northern half area of Río Muni (Fig. 1b). Forest elephant and forest buffalo had similar estimated occupancy probabilities (Table 2, Fig. 1c,d, respectively), although forest buffalo had a high estimated occurrence probability in the southwestern area. Among primate species, the estimated probabilities for the entire region ranged from 0.51 for gorilla, with a high distribution in the western and central areas of Río Muni (Fig. 1e), and 0.84 and 0.92 for mandrill and chimpanzee, respectively (Table 2), which both had a high distribution throughout the study area (Fig. 1f,g). The model-averaged estimates of the probability of detection were low for the two cat species and forest buffalo, but close to 1 for the rest of species (Table 2).


Integrating occurrence and detectability patterns based on interview data: a case study for threatened mammals in Equatorial Guinea
Estimated probabilities of occurrence for threatened mammals in Río Muni (Equatorial Guinea).All scales are occurrence probability per 25-km2 grid cell, calculated with the model averaging technique considering the most important models for each species showed in Supplementary Table S2. UTM coordinates are in zone 32N. Background maps in this figure have been generated by the authors using R version 3.2.5 (https://www.R-project.org/), and they have been incorporated in the corresponding panel using GIMP version 2.8.14 (https://www.gimp.org/). Outline maps of Africa and Equatorial Guinea has been drawn in R version 3.2.5 (https://www.R-project.org/) by using the maps and mapdata libraries (https://cran.r-project.org/web/packages/). Panels have been assembled with GIMP version 2.8.14 (https://www.gimp.org/).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036030&req=5

f1: Estimated probabilities of occurrence for threatened mammals in Río Muni (Equatorial Guinea).All scales are occurrence probability per 25-km2 grid cell, calculated with the model averaging technique considering the most important models for each species showed in Supplementary Table S2. UTM coordinates are in zone 32N. Background maps in this figure have been generated by the authors using R version 3.2.5 (https://www.R-project.org/), and they have been incorporated in the corresponding panel using GIMP version 2.8.14 (https://www.gimp.org/). Outline maps of Africa and Equatorial Guinea has been drawn in R version 3.2.5 (https://www.R-project.org/) by using the maps and mapdata libraries (https://cran.r-project.org/web/packages/). Panels have been assembled with GIMP version 2.8.14 (https://www.gimp.org/).
Mentions: Using the model averaging technique with top models for each species, we calculated average probabilities of occupancy and detection (Table 2) and developed corresponding occurrence maps for each species (Fig. 1). For most species, the average of the estimated probabilities of occupancy () was lower than the naïve estimate (i.e. observed proportion of occupied sites). The model-averaged estimates of the probabilities of occurrence () and detection () in all the cells of Río Muni region are shown in Table 2. Felids had restricted ranges ( = 0.19 for golden cat and  = 0.35 for leopard), especially golden cat throughout the area (Fig. 1a) and leopard in the northern half area of Río Muni (Fig. 1b). Forest elephant and forest buffalo had similar estimated occupancy probabilities (Table 2, Fig. 1c,d, respectively), although forest buffalo had a high estimated occurrence probability in the southwestern area. Among primate species, the estimated probabilities for the entire region ranged from 0.51 for gorilla, with a high distribution in the western and central areas of Río Muni (Fig. 1e), and 0.84 and 0.92 for mandrill and chimpanzee, respectively (Table 2), which both had a high distribution throughout the study area (Fig. 1f,g). The model-averaged estimates of the probability of detection were low for the two cat species and forest buffalo, but close to 1 for the rest of species (Table 2).

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus