Spatial overlap between sympatric wild and domestic herbivores links to resource gradients

Abstract

In this study, we investigated the relationship between resource gradients and overlap between wild and domestic herbivores in a southern African ecosystem. We used an Enhanced Vegetation Index (EVI) to identify and test the presence of resource gradients i.e. vegetation greenness between agricultural areas and conservation areas in Southeastern Zimbabwe, part of the Great Limpopo Transfrontier Conservation Area. We then tested whether these resource gradients coincide with GPS collared cattle (Bos taurus) movements into wildlife areas, as well as drive spatial overlaps between cattle and the GPS collared African buffalo (Syncerus caffer). Results showed that resource gradients although variable, exist between the conservation area and surrounding agricultural area. Cattle used the conservation area less than expected during the dry season when vegetation greenness in the communal land was relatively lower than in the conservation area. Significant spatial segregation between cattle and buffalo occurred during the wet season and late dry season, while spatial aggregation occurred during the early dry season. Intensity of habitat overlap between cattle and buffalo during the early dry season was relatively high in habitats preferred by both species. Our results suggest that cattle movement into conservation areas is linked to resource gradients. (Résumé d'auteur

Water and cattle shape habitat selection by wild herbivores at the edge of a protected area

“…Seasonal changes suggest access to resources is a key driver of cattle‐wildlife interactions (Zengeya et al ., ). During the rainy season, the widespread distribution of water pans allows buffalo and elephant to distribute themselves freely and avoid cattle that are herded into the protected area.…”

Remote Sensing of Environmental Drivers Influencing the Movement Ecology of Sympatric Wild and Domestic Ungulates in Semi-Arid Savannas, a Review

“…Vegetation indexes (Table 3) provide a synthetic description of the vegetation spatio-temporal dynamics and several studies have related SRS derived vegetation indices such as the NDVI or the Enhanced Vegetation Index (EVI) ( Table 3) to the spatio-temporal distribution and abundance of buffalo and other ungulates species at different scales [26,29,54,68,79,86,88,89,[145][146][147]. For example, Naidoo et al (2012a) used MODIS EVI time series to measure the greenness of the vegetation and demonstrated the importance of this variable in explaining the variations in home range size of buffaloes in northeastern Namibia [29].…”

“…In two Australian savanna study sites, Handcock et al (2009) showed that the tracks of cattle from GPS collars overlaid with a NDVI map derived from a 10 m resolution SPOT-5 image, highlighting a correlation between NDVI and cattle movements [26]. Using very high spatial resolution imagery, Zengeya et al (2015) derived a fine scale EVI map from an IKONOS image to determine the proportion of cattle home range observed inside and outside a conservation area [54]. Table 3.…”

“…Our review showed that the use of SRS to understand cattle or buffalo movement ecology mainly benefited from open-access products and standard image processing methods. EVI and NDVI are widely used vegetation indexes to characterize vegetation availability and evolution patterns in these studies [26,29,54,88,312]. However, other spectral indexes such as the Soil Adjusted Vegetation Index (SAVI) ( Table 3) that eliminate soil-induced variations in vegetation indexes [143] have not been used at all in existing buffalo and cattle movement studies.…”

“…Buffalo and cattle are both grazer ungulates, close phylogenetically, sharing common resources (i.e., forage and water) [50], and are thus likely to overlap in range and compete for resources, particularly in environments where resources are spatially segregated (e.g., savannas) [51,52]. Both species rely on their behavior and the management of the land use by humans to cope with constrained access to natural resources (e.g., access to artificial water, forage intake by the herder) [53,54]. Their shared use of space increases the likelihood of direct (i.e., the use of the same space at the same time) and indirect (i.e., the use of the same space at different times) contacts, which in turn promotes the risk of pathogen transmission [12,[55][56][57][58], a threat to farmers and biodiversity conservation [4,13].…”