Pastoral Ranches Research Articles

Hippopotamus and livestock grazing near water points: consequences for vegetation cover, plant species richness and composition in African savannas

Large mammals, such as hippopotamuses (Hippopotamus amphibius), can significantly alter the landscape, vegetation composition, and structure in savannas through their grazing habits and ecosystem engineering effects, especially around rivers. However, livestock grazing can strongly change these effects, as seen in the Kenyan Maasai Mara Ecosystem. In this region, the increasing intensity of livestock grazing along local rivers, resulting from the transition of Maasai pastoralists from a semi-nomadic lifestyle to one based on pastoral ranches near the Maasai Mara National Reserve, may alter the impact of hippo grazing on riparian vegetation. We investigated the differences in vegetation structure, plant species richness and composition between landscapes predominantly grazed by hippopotami and livestock. We studied 25 transects, each measuring 5 km and having 13 sampling plots of 10 × 10 m2 located at varying distances from rivers in the reserve (n = 16) and pastoral ranches (n = 9). We measured the height and estimated the percent cover of grasses, forbs, shrubs, and bare ground, as well as plant species composition and richness and grazing intensity. Our results show that the riverine areas were more intensely and homogeneously grazed in the pastoral ranches than in the reserve, and in the dry than in the wet season in both landscapes. In addition, grazing intensity decreased with distance from rivers in the reserve in both seasons, but only in the wet season in the pastoral ranches. The mean plant species richness was similar in both landscapes and decreased linearly with distance from rivers, but varied with grazing intensity due to differences in forb and shrub species. However, plant species composition differed significantly between the reserve and the pastoral ranches. Furthermore, species similarity indices declined with increasing distance from water. These results suggest that the effects of livestock and hippo grazing intensity on vegetation structure and spatial heterogeneity interact, and vary with landscape and season. While both hippopotamus and livestock grazing can modify riparian vegetation, livestock grazing impact on plant species composition, vegetation structure, and spatial heterogeneity appears to be more persistent, declining less rapidly with increasing distance from water. Consequently, hippo and livestock differentially impact landscape heterogeneity.

The value of pastoral ranches for wildlife conservation in the Kalahari

Abstract Context Rangelands can play an important role in conservation by providing additional habitat for many threatened species and maintaining global biodiversity. Identifying areas that can integrate both pastoral and conservation activities is important for capturing benefits from wildlife in non-protected areas. Aims To investigate wildlife distribution in a contiguous landscape comprising both pastoral ranches and wildlife-based areas in western Botswana. Methods We deployed motion-activated camera traps to assess mammal richness and occupancy using a multi-species occupancy model. We tested whether environmental factors influenced these parameters in a commercial ranching block in the western Kalahari region of Botswana, and whether species-specific occupancy varied between ranches and neighbouring wildlife management areas. Key results In the ranching block, vegetation, season and distance to wildlife areas influenced species-specific occupancy and species richness, whereas farm type and water availability affected only a few carnivore species. Commercial ranches supported several threatened species such as African wild dog, cheetah and pangolin, and we detected two species, African civet and serval, not previously considered being present in this region. Mammal diversity was similar between ranches and wildlife areas, but species composition varied. Land use affected species-specific occupancy, with many carnivore species occurring close to or in wildlife areas. Conclusions We showed that commercial ranches in the Kalahari are utilised by many mammal species, and these areas may play an important role in the conservation of threatened species. Understanding species-, group- and community-level responses to the impacts of human activities in rangelands is vital as the need for pastoral land increases. Implications We predicted regions of high occurrence of carnivores that can be important for tackling human–wildlife conflict as well as regions with high species diversity that may be useful for increasing integration of conservation endeavours (e.g. eco-tourism) that promote the benefits of wildlife in predominantly livestock regions.

Population regulation of African buffalo in the Mara–Serengeti ecosystem

Context The processes regulating ungulate populations have been the focus of numerous studies. For the African buffalo (Syncerus caffer Sparrman) population inhabiting the Mara–Serengeti ecosystem, rinderpest was the primary regulatory factor up to the mid-1960s. Following reduction of rinderpest and buffalo population increase, interspecific competition for food, notably with cattle and wildebeest (Connochaetes taurinus Burchell), was thought to be the primary regulatory factor in the ecosystem. Aims We analysed buffalo population trends and the relationship between buffalo population growth and rainfall and density dependence in the Mara–Serengeti ecosystem and discuss the findings in the context of the key ecosystem processes governing buffalo population dynamics in African savannas, namely, food limitation, competition, predation, disease and land use changes. Methods We analysed buffalo population dynamics in the Mara–Serengeti ecosystem in relation to rainfall and density dependence feedback between 1984 and 2010. Key results Buffalo population growth was both significantly density-dependent and positively correlated with the dry season rainfall after, but not before, a severe drought in 1993. Buffalo numbers crashed by 48.6% in 1984–85 and by 76.1% in 1993–94 during severe droughts when food availability was lowest and competition with the more numerous cattle and wildebeest was highest. Conclusions Recovery of buffalo numbers to pre-drought levels took 8–9 years after the 1984–85 drought but was much slower, with buffaloes numbering merely 36% of their 1993 population (12 895 animals) 18 years after the 1993–94 drought despite intermittent periods of high rainfall, probably due to demographic and/or reproductive factors, heightened competition with livestock, land use changes in the adjoining pastoral ranches, lion predation and recurrent severe droughts. Implications Our findings demonstrate how food limitation caused by droughts associated with the hemispheric El Niño–Southern Oscillation can cause severe declines in and threaten the persistence of large ungulate populations. The findings also portray how density-dependent food limitation, competition, predation, land use changes and other factors can accentuate the effect of droughts and greatly prolong population recovery.

Large herbivore responses to surface water and land use in an East African savanna: implications for conservation and human-wildlife conflicts

Water, forage and predation constrain ungulate distributions in savannas. To understand these constraints, we characterized distributions of 15 herbivore species from water, locations of peak density and degree of clustering around the peaks using zero-inflated count data models and mapping census data collected in the Mara reserve and the adjoining pastoral ranches in Kenya during a wet and dry year. Herbivores followed a humped pattern (n = 46), suggesting constrained foraging in which they balance the benefits of proximity to water with the costs of foraging where food is depleted near water and travelling to more abundant food distant from water; an exponentially decreasing pattern (n = 11), indicating strong attraction to water or vegetation near water; or a uniform (n = 3) pattern. The details rather than the types of these patterns varied between years. Herbivores concentrated farther from water and more tightly around locations of their peak densities in the ranches than the reserve. Herbivores were more abundant and widely distributed from water in the wet than the dry year, and segregated along the distance-to-water gradient, presumably to minimize interspecific competition for food. Pastoralism compressed herbivore distributions and partially excluded some species (warthog, hartebeest, topi, wildebeest, zebra, eland, buffalo and elephant) from, while attracting others (Grant’s and Thomson’s gazelles, impala, giraffe) to the ranches, relative to the reserve. Regulating cultivation, fencing, settlements and livestock stocking levels in the ranches would allow continued wildlife access to water, reduce competition with, displacement or harassment of wildlife by people, livestock and dogs near water.

The distribution of large herbivore hotspots in relation to environmental and anthropogenic correlates in the Mara region of Kenya

1. The distributions of large herbivores in protected areas and their surroundings are becoming increasingly restricted by changing land use, with adverse consequences for wildlife populations. 2. We analyse changes in distributions of herbivore hotspots to understand their environmental and anthropogenic correlates using 50 aerial surveys conducted at a spatial resolution of 5 × 5 km(2) (n = 289 cells) in the Mara region of Kenya during 1977-2010. We compare the distributions across seasons, land use types (protection, pastoralism and agro-pastoralism) and 10 species with different body sizes and feeding styles. 3. Small herbivores that are the most susceptible to predation and dependent on high-quality forage concentrate in the greenest and wet areas and close to rivers in Masai pastoral ranches in both seasons. Livestock grazing creates conditions favouring small herbivores in these ranches, including high-quality short grasses and better visibility, implying facilitation. But in the reserve, they concentrate in browner, drier and flatter areas and farther from rivers, suggesting facilitation by large grazers in the wet season, or little competition with migratory herbivores occupying the reserve in the dry season. 4. In the wet season, medium herbivores concentrate in similar areas to small herbivores in the ranches and reserve. However, in the dry season, they stay in the reserve, and also concentrate in green and wet areas close to rivers when migrants occur in the reserve. As such areas typically have higher predation risk, this suggests facilitation by the migrants by absorbing most predation pressure or, alternatively, competitive displacement by the migrants from preferred habitats. 5. Large herbivores, which suffer the least predation, depend on bulk forage and are the most likely to engender conflicts with people, concentrate in the reserve all year. This suggests attraction to the taller and denser grass and perceived greater safety in the reserve in both seasons. 6. These results reveal how predation risk, forage quantity and quality, water, competition with and facilitation by livestock interact with individual life-history traits, seasons and land use in shaping the dynamics of herbivore hotspots in protected and human-dominated savannas.

Comparative changes in density and demography of large herbivores in the Masai Mara Reserve and its surrounding human-dominated pastoral ranches in Kenya

Wildlife habitats in pastoral lands adjoining protected areas in east African savannas are getting progressively degraded, fragmented and compressed by expanding human populations and intensification of land use. To understand the consequences of these influences on wildlife populations, we contrasted the density and demography of 13 wild and three domestic large herbivores between the Masai Mara National Reserve and the adjoining pastoral ranches using aerial surveys conducted in the wet and dry seasons during 1977–2010. Species of different body sizes and feeding styles had different densities between landscapes and seasons. Small-sized herbivores, requiring short, nutritious grasses, and browsers were more abundant in the ranches than the reserve in both seasons. Medium-sized herbivores moved seasonally between landscapes. Larger-bodied herbivores, requiring bulk forage but less susceptible to predation, were more abundant in the reserve than the ranches. The proportions of newborn warthog (Phacochoerus africanus) and juvenile topi (Damaliscus korrigum) were higher in the ranches, with shorter grasses and lower predation risk than in the reserve. These results suggest that pastoral lands adjoining protected areas in African savannas are important as seasonal dispersal and breeding grounds for wild herbivores. However, human population growth and dramatic land use changes are progressively degrading wildlife habitats in pastoral areas, thus restricting the seasonal wildlife dispersal movements between the protected areas and adjoining pastoral lands. Conservation efforts should focus on (1) creating and maintaining functional heterogeneity in protected areas that mimic moderate pastoral grazing conditions to attract small and medium-bodied grazers and (2) securing dispersal areas, including corridors, to ensure continued seasonal large herbivore movements between protected and pastoral systems.

Hippopotamus and livestock grazing: influences on riparian vegetation and facilitation of other herbivores in the Mara Region of Kenya

Riparian savanna habitats grazed by hippopotamus or livestock experience seasonal ecological stresses through the depletion of herbaceous vegetation, and are often points of contacts and conflicts between herbivores, humans and their livestock. We investigated how hippopotamus and livestock grazing influence vegetation structure and cover and facilitate other wild herbivores in the Mara region of Kenya. We used 5 km-long transects, each with 13 plots measuring 10 × 10 m2, and which radiate from rivers in the Masai Mara National Reserve and adjoining community pastoral ranches. For each plot, we measured the height and visually estimated the percent cover of grasses, forbs, shrubs and bare ground, herbivore abundance and species richness. Our results showed that grass height was shortest closest to rivers in both landscapes, increased with increasing distance from rivers in the reserve, but was uniformly short in the pastoral ranches. Shifting mosaics of short grass lawns interspersed with patches of medium to tall grasses occurred within 2.5 km of the rivers in the reserve in areas grazed habitually by hippos. Hence, hippo grazing enhanced the structural heterogeneity of vegetation but livestock grazing had a homogenizing effect in the pastoral ranches. The distribution of biomass and the species richness of other ungulates with distance from rivers followed a quadratic pattern in the reserve, suggesting that hippopotamus grazing attracted more herbivores to the vegetation patches at intermediate distances from rivers in the reserve. However, the distribution of biomass and the species richness of other ungulates followed a linear pattern in the pastoral ranches, implying that herbivores avoided areas grazed heavily by livestock in the pastoral ranches, especially near rivers.

Continuing wildlife population declines and range contraction in the Mara region of Kenya during 1977–2009

Populations of many wild ungulate species in Africa are in decline largely because of land-use changes and other human activities. Analyses that document these declines and advance our understanding of their underlying causes are fundamental to effective management and conservation of wild ungulates. We analyzed temporal trends in wildlife and livestock population abundances in the Mara region of Kenya. We found that wildlife populations in the Mara region declined progressively after 1977, with few exceptions. Populations of almost all wildlife species have declined to a third or less of their former abundance both in the protected Masai Mara National Reserve and in the adjoining pastoral ranches. Human influences appeared to be the fundamental cause. Besides reinforced anti-poaching patrols, the expansion of cultivation, settlements and fences and livestock stocking levels on the pastoral ranches need to be regulated to avoid further declines in the wildlife resource.

The effects of pastoralism and protection on lion behaviour, demography and space use in the Mara Region of Kenya

Contraction of their historic geographic ranges and conflicts with humans underpins declines in large carnivore populations worldwide. These declines, which characterize pastoral systems where carnivores, people and livestock live in close contact, may be paralleled by changes in carnivore behaviour. We investigated this by comparing the behaviour, demography and space-use of three lion (Panthera leo ) prides in the protected Masai Mara National Reserve and the adjoining Koyiaki pastoral ranch in southwestern Kenya during 2005–2006. The mean times lions were inactive was similar between the three prides except when the ranch lions were severely disturbed and became more nocturnal and inactive. The reserve lions ate their kills on open plains and returned to them often but the ranch lions did so only inside bushes and abandoned unfinished kills during a drought in 2005. The reserve lions spent most of their time on open plains while the ranch lions did so in bushes and woodlands. Activity budgets were similar between the prides regardless of land use. Adult lions altered not so much the type but the spatial location and timing of their behaviour on the pastoral ranches relative to the reserve.We discuss the implications of these findings for lion conservation on pastoral lands.

The Effects of Pastoralism and Protection on Lion Behaviour, Demography and Space use in the Mara Region of Kenya

Contraction of their historic geographic ranges and conflicts with humans underpins declines in large carnivore populations worldwide. These declines, which characterize pastoral systems where carnivores, people and livestock live in close contact, may be paralleled by changes in carnivore behaviour. We investigated this by comparing the behaviour, demography and space-use of three lion (Panthera leo ) prides in the protected Masai Mara National Reserve and the adjoining Koyiaki pastoral ranch in southwestern Kenya during 2005–2006. The mean times lions were inactive was similar between the three prides except when the ranch lions were severely disturbed and became more nocturnal and inactive. The reserve lions ate their kills on open plains and returned to them often but the ranch lions did so only inside bushes and abandoned unfinished kills during a drought in 2005. The reserve lions spent most of their time on open plains while the ranch lions did so in bushes and woodlands. Activity budgets were similar between the prides regardless of land use. Adult lions altered not so much the type but the spatial location and timing of their behaviour on the pastoral ranches relative to the reserve.We discuss the implications of these findings for lion conservation on pastoral lands.

Population trend and distribution of the Vulnerable common hippopotamus Hippopotamus amphibius in the Mara Region of Kenya

AbstractThe common hippopotamus Hippopotamus amphibius can significantly influence the dynamics of ecosystems and engender serious conflicts with people but, in Kenya, one of the species strongholds, it has been little studied or monitored. We surveyed the hippopotamus population in the Masai Mara National Reserve and the adjoining pastoral ranches in 2006 using foot counts along 155.3 km of the main rivers. We counted 4,170 hippopotamuses in 171 schools. Comparisons with earlier surveys suggest that this population increased by 169.6% between 1971 and 1980 within the reserve and, although it did not increase within the reserve during 1980–2006, it increased by 359.4% outside the reserve during this period against a background of deteriorating habitat conditions. The overall density in 2006 was 26.9 hippopotamuses km-1 of river, equivalent to a biomass of 26,677 kg km-1 of river. The ratio of calves to 100 adults was 9:100 inside the reserve, 10:100 outside the reserve and 6:100 along tributaries of the Mara River, implying that the population is either increasing or that its spatial distribution is being compressed because of range contraction. The apparent increase in the hippopotamus population contrasts with marked contemporaneous declines in the populations of most other large mammalian herbivore species in the Reserve. We discuss possible reasons underlying the increase in the hippopotamus population.

Dynamics of births and juvenile recruitment in Mara–Serengeti ungulates in relation to climatic and land use changes

AbstractNatality and recruitment govern animal population dynamics, but their responses to fluctuating resources, competition, predation, shifting habitat conditions, density feedback and diseases are poorly understood. To understand the influences of climatic and land use changes on population dynamics, we monitored monthly changes in births and juvenile recruitment in seven ungulate species for 15 years (1989–2003) in the Masai Mara Reserve of Kenya. Recruitment rates declined for all species but giraffe, likely due to habitat alteration and increasing vulnerability of animals associated with recurrent severe droughts, rising temperatures, unprecedentedly strong and prolonged El Niño‐Southern Oscillation (ENSO) episodes, expansion of settlements, cultivation and human population growth in pastoral ranches adjoining the reserve. Birth rate showed strong and humped relationships with moving averages of monthly rainfall, whereas recruitment responded strongly to cumulative past rainfall. Increasing livestock incursions into the reserve depressed recruitment rate for quarter‐grown topi. Expansion of pastoral settlements depressed birth rate in impala, zebra and giraffe. Frequent ENSO‐related droughts caused progressive habitat desiccation and hence nutritional shortfalls for ungulates. The responses to climatic, land use and resource influences did not reflect body size, migratory or resident lifestyle, dietary guild, digestive physiology or degree of synchrony of breeding of the ungulate species.

Dynamics of Mara–Serengeti ungulates in relation to land use changes

AbstractAnimal population dynamics can be driven by changing climatic forcing, shifting habitat conditions, trophic interactions and anthropogenic influences. To understand these influences, we analyzed trends in populations of seven ungulate species counted during 15 years (1989–2003) of monthly monitoring using vehicle ground counts in the Maasai Mara National Reserve, Kenya. Abundance of six species declined markedly and persistently throughout the reserve during this period. The declines were contemporaneous with progressive habitat deterioration due to changing land use in pastoral ranches bordering the reserve, habitat desiccation due to rising temperatures, recurrent severe droughts and an exceptional ENSO flood in 1997–1998. The effect of progressive habitat deterioration was accentuated by illicit harvest, competition with livestock and elevated predation. After factoring out the influence of rainfall, ungulate populations declined more markedly in sections of the reserve experiencing greater livestock incursions and poaching. The declines were significantly correlated with increasing number of settlements and people in the pastoral ranches for five species. Heightened predation following a crash in the buffalo Syncerus caffer population during a severe drought in 1993 had little support as the primary cause of the declines.

Influence of cultivation, settlements and water sources on wildlife distribution and habitat selection in south-east Kajiado, Kenya

SUMMARYIn Kenya, lands surrounding wildlife protected areas (PAs), referred to as dispersal areas, have undergone widespread land use changes, but these have been little studied. This study investigated impacts of different land use types on wildlife distribution and composition. Transect data from stratified random sampling based on land use and vegetation type were analysed using correlation and canonical correspondence analysis (CCA). Household density and cultivation intensity were negatively correlated with grass cover and were greatest on small-scale farms and lowest in a dedicated PA. Three patterns of wildlife distribution were identified. Wildlife density in communal grazing and the PA was significantly higher than on other land use types. While most wildlife used pastoral ranches in the wet season, larger herbivores moved to the PA during the dry season. Wildlife density along the grass cover gradient, which was a disturbance gradient, was dome shaped, indicating that wildlife tolerated moderate levels of disturbance. The primary factors influencing wildlife distribution were vegetation type and proximity to water sources in the dry and wet seasons, respectively. The apparent anomaly in the wet season is attributed to wildlife moving from Chyulu, which lacked seasonal ponds, to the lowland Masaai ranches, which had plenty of ponds. In both seasons, cattle density was the most important secondary factor. To mitigate declining wildlife trends, management should ensure a heterogeneity of vegetation types is maintained and wildlife retain access to seasonal water sources.

The effects of pastoralism and protection on the density and distribution of carnivores and their prey in the Mara ecosystem of Kenya

The overlap of large carnivores, livestock and people can engender conflicts that often threaten the future viability of carnivore populations in the pastoral systems of Africa. A playback survey of lions Panthera leo, spotted hyenas Crocuta crocuta and black-backed jackals Canis mesomelas and a transect count of wild herbivores was conducted in the Maasai Mara National Reserve and adjoining pastoral ranches to assess the effect of pastoralism and protection on the density and distribution of carnivores in June 2003. Reliability of the prey counts depended on an assumption of similar observability between the protected and pastoral areas, which we assessed using distance sampling in November 2003 and computer simulations and determined to be similar. Estimates of wild prey biomass density was 2.6 times higher in the ranches (14212 kg/km2) than in the reserve (5472 kg/km2) during this wet season count. Apparent hyena density estimates were 1.3 times higher in the ranches (0.561 hyenas/km2) than in the reserve (0.404 hyenas/km2), in correspondence with the regional pattern of prey density. This distribution of hyenas is biased towards the reserve, if it is dependent on prey density. Estimates of apparent jackal density were similar in both areas whereas lion density was anomalously 8.0 times lower in the ranches (0.046 lions/km2) than in the reserve (0.369 lions/km2). Lion and hyena densities and prey biomass did not differ between June 1991 (5172.273 kg/km2) and June 2003 (5472 kg/km2) in the reserve, but jackal density increased in the same period. Lions never responded to playbacks in the ranches, so the potential shift in lion behavioural response for different land use zones is another potential explanation for the patterns found here. We think a real shift in lion populations is a better explanation than a behavioural change in relation to playbacks based on additional data from independent systematic and intensive censuses and playback surveys conducted in the ranches. Lion populations in the pastoral ranches seemed headed for extinction, probably owing to conflicts with pastoralism, necessitating urgent conservation interventions that integrate pastoral economic welfare with large carnivore conservation goals to foster long-term viability of lion populations in the pastoral systems.