Abstract:
Bushpigs (Potamochoerus larvatus) play a major role in the socio-ecosystem of Madagascar, particularly in rural areas. They are largely hunted by rural populations as a major source of income and protein. They can also represent a potential source of pathogens for domestic animals and people. For example, it is hypothesized that bushpigs might compromise African swine fever (ASF) eradication programs by sporadically transmitting the virus to domestic pigs. However, available knowledge on the distribution of bushpigs in Madagascar is limited. In this study, we estimated the distribution of bushpigs on Madagascar using a species distribution model (SDM). We retrieved 206 sightings of bushpigs in Madagascar during 1990–2016 and predicted the distribution by using 37 climatic, geographic, and agricultural/human variables related to the presence of bushpigs and running a presence-background maximum entropy SDM. Our model identified three main areas with a high suitability for bushpigs: in the north, central-western, and east of the island (AUC = 0.84). The main contributors to the model were the vegetation index (51.3%), percentage of land covered by trees (17.6%), and annual averaged monthly precipitation (12.6%). In addition, we identified areas in central Madagascar with a high density of domestic pigs and a high suitability score for bushpigs. These results may help to identify bushpig areas at the interface with domestic pigs to assess the risk of pathogen transmission and to design ecological assessments, wildlife management studies, or targeted surveillance and research studies related to many bushpig-borne pathogens, such as ASF, which is an endemic problem in the country, as well as zoonotic diseases such as cysticercosis and hepatitis E. Our approach could also be extrapolated to other species of wild swine in other countries.
Description:
DATA AVAILABILITY : The data supporting the findings of this study are available from the corresponding author upon request.
SUPPLEMENTARY MATERIAL : SUPPLEMENTARY FIGURE 1: Spatial and temporal distribution of the total number of observations of bushpigs originally gathered (n = 206, left) and of the observations included in the ecological niche model (n = 83, right) after correction for pseudoreplication. SUPPLEMENTARY FIGURE 2: The Spearman’s correlation matrix of the 36 environmental variables selected for the study. SUPPLEMENTARY FIGURE 3: The map of the density of pigs (no. of heads/km2) in Madagascar. SUPPLEMENTARY FIGURE 4: Variation in the repetition of the MaxEnt analysis resampling different presence points: (a) the final model presented in the study and used as a reference; (b) the map of the average absolute difference in the predicted output between each of the 1,000 analyses and the reference map; and (c) maximum, 95th percentile, and median of the variation (in %) from the reference map for each of the 1,000 iterations. SUPPLEMENTARY TABLE 1: Variables considered for the ecological niche model and source. SUPPLEMENTARY CODE 1: Example of an R code to correct for pseudoreplication.
