Comparison of Three Methods to Assess the Potential for Bushpig-Domestic Pig Interactions at the Wildlife—Livestock Interface in Uganda

Abstract

Bushpigs (Potamochoerus larvatus) are considered a nuisance to farmers because of their crop raiding habits. Through their incursions into farmlands, they may interact with free-ranging domestic pigs and potentially cause transmission of infectious diseases such as African Swine Fever (ASF). The role of the bushpig in the epidemiology of ASF is poorly known and one of the gaps of knowledge is precisely the nature of interaction between bushpigs and domestic pigs. Thus, in this study, we investigated the frequency of bushpig visits to crop fields in rural communities where ASF is endemic, at the edge of a wildlife protected area in northwestern Uganda, to better understand the potential for interaction and disease transmission. We used three methods (questionnaires, camera traps, and observations for tracks) to assess bushpig visits to farmland. These methods were implemented concurrently in 28 farms during rainy and dry seasons. The results obtained by each of the three methods were analyzed by generalized linear mixed models. Potential risk factors including crop type, season, and landscape characteristics related to bushpig ecology were tested as explanatory variables. A generalized linear model and the Kendall test were used to compare the results and consistency of the frequency values obtained by the three methods. A high percentage (75%) of interviewed farmers reported visits from bushpigs in 29.6% of assessed crops (n = 145), and a frequency of 0.014 +/−0.05 visits per night was obtained through camera-trapping. Bushpig tracks were detected in 36% of sessions of observation. Cassava (Manihot esculenta) and groundnut (Arachis hypogaea L.) crop fields were the most visited, and these visits were more common during the rainy than the dry season. Distances from crop sites to the boundary of the protected area and to the river also influenced visit frequency. Camera-trapping was the least sensitive method while questionnaires and track observations presented consistent and complementary results to characterize spatial and temporal visits of bushpig into the crop fields. Evidence from our study shows that when used in combination, these methods can provide useful data to improve our understanding of the interactions between bushpigs and domestic pigs at the wildlife-domestic interface.

Free-Ranging Pig and Wild Boar Interactions in an Endemic Area of African Swine Fever

“…Different approaches have been taken to study animal interactions, such as questionnaires (26, 29), direct observations (30, 31), and telemetry (24, 25, 28). Another method is camera trapping, which provides a non-invasive way to collect direct and visual evidence of interactions (23, 32–34).…”

Spatial-Temporal Movements of Free Ranging Pigs at the Wildlife-Livestock Interface of Murchison Falls National Park, Uganda: Potential of Disease Control at a Local Scale

“…Although ecological studies documenting the spatial dimension of domestic pig movements are scarce in the African context, one study addressed this topic in Kenya ( 29 ). However, this is the first time that this approach is implemented in the context of an ASFV infected area at the interface of a wildlife national park where the presence of a warthog—tick sylvatic cycle and the sympatric presence of warthogs and bushpigs with domestic pigs is well described ( 22 , 24 ). The small number of pigs we had in our study limits the robustness of our results.…”

“…The vegetation consists of mostly savannah and the region is covered by a mixture of grassland and farmland interspersed by small woods. The major crops cultivated in Nwoya district are groundnuts, beans, maize, rice, cassava and sesame ( 24 , 25 ). The major livestock species in Nwoya district are cattle, goats, sheep and pigs ( 22 ).…”

“…As previous studies carried out in the same study sites pointed out that waterpoints and crops may be items at risk for interactions between domestic and wild pigs ( 22 , 24 ), we focused on these two items by checking if their use was different between day and night and between the rainy and the dry seasons. We kept the definition of daytime and night time and used the same tests and software as for the activity pattern (see paragraph Home Range, Daily Distance, and Activity Pattern).…”

Do wild suids from Ndumo Game Reserve, South Africa, play a role in the maintenance and transmission of African swine fever to domestic pigs?

“…While natural hybridization between domestic pigs and warthogs has not been reported, there are a number of reports of cross‐breeding between bushpigs and domestic pigs (Jori & Bastos, 2009; Kingdon, 2015). It is, therefore, assumed that while interactions could occur, they are not necessarily observed due to the elusive and nocturnal behaviour of bushpigs (Payne et al., 2018). Incursions of bushpigs in farming areas are likely to occur at night and warthogs might have human avoidance behaviour (Kassilly et al., 2008).…”