Spatial Distribution of Kalahari Common Eland, Gemsbok and Blue Wildebeest in Relation to Free-Ranging Livestock Grazing Gradient and Land Use, Botswana
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Spatial distribution of Kalahari Common Eland, Gemsbok and Blue Wildebeest in relation to free-ranging livestock grazing gradient and land use, Botswana. Akanyang L.1, Carver S.1 and Benton T. G.2 1School of Geography, Faculty of the Environment, University of Leeds. 2School of Biology, Faculty of Biological Sciences University of Leeds. January 11, 2017 Summary Large herbivores distributions within pastoralism areas and surrounding protected areas are restricted by changing land use. We studied the spatial distribution of three large herbivores in relation to livestock grazing gradient during the wet and dry seasons, using spoor information, roads side counts, and vegetation surveys. Most livestock grazing distribution were mainly closer to settlements, cattle posts in Communal Grazing Areas, with very few observations in Wildlife Management Areas (WMAs). Large herbivores were sensitive to livestock grazing intensity and human-induced risk hence concentrated in WMAs. Suggesting that human-induced risk, such illegal hunting, human disturbance are most significant factors influencing large herbivores distribution. KEYWORDS: large herbivores, spatial distribution pattern, Pastoralism, Kalahari, human-induced risk Extended Abstract 1.1 Introduction Livestock and wildlife share land, water and forage resources in savanna rangelands (Young et al., 2005) In most of Africa, especially in Kalahari, Botswana, human settlements and pastoralism activities have invaded wildlife habitat, resulting into pastoralists, free ranging livestock and large herbivores interactions. Land use changes, such as settlements and Pastoralism activities influence the distribution of large herbivores in Communal Grazing Areas (CGAs) and their surrounding Wildlife Management Areas (WMAs). However, few studies have really measured the resource partitioning ability and spatial distribution patterns between free ranging livestock and large herbivores in southern African savanna. Therefore the aim of the study was to explore the interactions between Pastoralists, free-ranging livestock and large herbivores during wet and dry seasons in communal grazing areas and their surrounding Wildlife Management Areas. To understand these interactions, we analysed the spatial distribution patterns of three large herbivores (Common Eland Tragelaphus oryx (Pallas), Gemsbok Oryx gazella (Linnaeus) and blue Wildebeest Connochaetes taurinus (Burchell)) during wet and dry season for a period of two years, along the livestock (i.e. cattle - Bos taurus (Linnaeus) grazing gradient and other pastoralists’ activities in the Kalahari rangelands, Botswana. 1.2. Methods The methods involved large herbivores and livestock spoor (tracks, pellets) information and roads side counts along five 60km transects radiating from the major settlements (Figure 1) in two years, covering two dry seasons (August to October 2014 & 2015) and two wet seasons (March to May 2015 & 2016). Wildlife and livestock spoor information at each sample point were classified as none, low, moderate, and high distribution depending on the intensity of tracks and the number of animal pellets counted per sample point. In addition forage availability (herbaceous and shrub cover (%)) and livestock grazing intensity were estimated and each sample point. The spatial distribution of pastoralists’ activities, such as cattle posts (Figure a & b), Agriculture fields (Figure 2 c & d) and remote access roads were produced using ARCGIS and Google earth images (2014), while the grazing distribution of free raging livestock from the watering points and cattle posts were determined through monitoring different livestock using the GPS collars (Figure 4 a & b) during wet and dry seasons. Figure 1: The location of five 60 km transects and sample points (brown dots) radiating from the major villages (Lehututu, Hukuntsi, Lokgwabe and Tshane) and cutting across communal grazing and wildlife management areas 2. Major results 2.1 Free-ranging livestock distribution As expected all livestock (cattle) distribution were mainly in Communal Grazing Areas during wet and dry seasons (Figure 3 c & d), a pattern similar to the past studies elsewhere (de Leeuw et al., 2001, Verlinden, 1997, Verlinden et al., 1998). There were very few observations of livestock grazing in the WMAs, excluding that livestock which was coming from the cattle posts located within (e.g. Zutshwa settlement) and near (e.g. Kgamatholo, Thupa ya mokala, Tjawane) WMAs. Most of the cattle distribution and abundance were along Lehututu/Hunhukwe, followed by Hukuntsi/Zutshwa & Hukuntsi/Ngwatle and were associated with settlements, cattle posts, boreholes, and positively related to bush encroachment. A likely explanation for this livestock grazing distribution pattern is due to the location of most cattle posts (Figure 2) and water points (boreholes), which are within CGAs. Therefore, cattle were grazing within a certain radius (average 15km) from these cattle posts or water points, hence clustering around them (de Leeuw et al., 2001). Cattle posts density was closer to the settlements because many watering points were located within the larger pans near the major settlement, hence overgrazing by livestock within a radius of 20 km from these major villages. In CGA there is reduced grass cover due to livestock grazing intensity (Skarpe, 1986), up to 20km from the settlements (Moleele and Mainah, 2003). Cattle have adapted to eat bulk grasses even of lower quality (Demment and Van Soest, 1985); hence utilizing most of the grass biomass within the 20km distance from the village. The vegetation surveys for the present study show that within the 20km radius from these water sources, grass cover has been reduced to bare ground cover (Figure 3 a & b), promoting bush encroachment (Walker et al., 1981). Intensive livestock grazing was associated with high tree density, less grass cover, unpalatable perennials grass closer to water sources, cattle posts and settlements, suggesting bush encroachment a result of the high intensity of livestock grazing in these areas. Livestock reduces competition from herbaceous vegetation (Jacobs and Naiman, 2008, Knoop and Walker, 1985, Walker et al., 1981), hence promoting shallow rooted woody plants through increased soil moisture and nutrients. During the wet season annual grasses (mainly Schimidtia kalaharensis Stent) and forbs species covered these intensively grazed areas, while Eragrostis lehmanniana Nees covered the moderately grazed areas (Dougill et al., 2016, Jacobs and Naiman, 2008, Knoop and Walker, 1985, Walker et al., 1981). The grass species mentioned above are less nutritious than other grasses species such as Schmidtia pappophoroides Steud ex J.A. Schmidt, Anthephora pubescens Nees and Eragrostis pallens Hack. Ex Schinz, which increase with increasing distance from water sources and cattle posts. Hence during the dry season, cattle grazing within 20km from the primary water sources depended mainly on browsing (Le Houérou, 1980, Moleele, 1998). While in the wet season, they benefited from the less nutritious annual grasses (e.g. Schimidtia kalaharensis), perennial grasses (e.g. Eragrostis lehmanniana), forbs and browsing. Therefore, cattle traveled longer distances for grazing during dry than in wet season (Figure 4c & d). Implying competition between free-ranging livestock and large herbivores within the intensively grazed areas, especially during dry season when the grazing resources are limited (Odadi et al., 2011). Cattle posts within the study area study the within posts Cattle a b Arable agriculture fields within the study area study the within fields agriculture Arable c d Figure 2: Spatial distribution of cattle posts (brown triangles) (a & b) and arable agriculture fields (green polygons) (c & d) within the study area. Most of the cattle posts are located closer to the settlements and arable agriculture fields. Total grass cover (%) relative to grazing gradient to grazing relative (%) cover grass Total a b intensity Livestock grazing grazing Livestock c d Figure 3: Herbaceous cover (%) along livestock grazing gradient (a & b) and livestock grazing intensity (c & d) during dry and wet seasons respectively. cattle collared with GPS trackers GPS with collared cattle s Example of movement of Example a b distribution during dry and wet season and wet dry during distribution Cattle grazing grazing Cattle c d Figure 4: Example of movement of GPS collared cattle (a & b), different colours of the dots represent different movements of individual collared animal. Figure 4a, shows the movement of all collared cattle at a small scale, while Figure 4b shows movement of animals from one cattle posts. C and D show livestock grazing distribution in relation to cattle posts during dry and wet season respectively as determined from the collared animals. Cattle travelled longer distances for grazing during dry (c) than in wet (d) season. 2.2. Common Eland, Gemsbok and Blue Wildebeest distribution patterns Despite the fact that Common Eland (68%) and Gemsbok (51%) are one of the most abundant wildlife species in Kgalagadi district as compared to the whole country (DWNP, 2012), the present study findings show that these species were rare. Their spoor information was only recorded along Lokgwabe/Mabuasehube, Tshane/Kang & Hukuntsi/Ngwatle and but no observations along other transects. Eland, Gemsbok, and Blue Wildebeest concentrated within WMAs at greater distances from settlements, cattle posts, and boreholes (Figure 5). They were associated with areas