Foraging ecology of roan antelope: key resources during critical periods

The use of landscape zones and grass species by roan antelope, a species threatened with local extirpation within South Africa's Kruger National Park, were investigated. Plant‐based observations of grazing were made within a 300 ha enclosure in the roan range, where 40 roan antelope were confined at high density in the absence of other grazers. The study spanned the dry seasons of two years, one with average rainfall and one with low rainfall. We recorded changes in the extent of grazing of different grass species, height differences between grazed and ungrazed tillers and intensity of cropping per tuft. In the average year, the grazing pressure in the bottomland grassland was twice that in the upland savanna, with two tall grass species bearing the brunt of the grazing through the dry season. Two highly palatable upland grasses were also extensively grazed by the mid dry season. In the dry year, the extent of grazing in the upland exceeded that in the bottomland, and several upland grass species little used the previous year became heavily grazed. Roan antelope appeared to be separated ecologically from more common grazers by their selective use of tall grasses growing in the drainage line grassland during the critical dry season months. However, their grazing expansion into the upland savanna during the dry year potentially brought them into competition with these grazers. Nevertheless, their population performance did not suffer despite the high‐density conditions. Heightened predation pressure following an influx of these grazers, rather than resource limitation, appeared to be primarily responsible for the drastic decline of this species in the park.     

Modelling ungulate dependence on higher quality forage under large trees in African savannahs

In African savannahs, large trees improve grass quality, particularly in dry and nutrient poor areas. Enhanced below-canopy grass nutrients, such as nitrogen and phosphorus contents should therefore attract and benefit grazers. To predict whether ungulates really need these forage quality islands we focused on four grazer species, i.e., zebra, buffalo, wildebeest, and warthog, differing in body size and digestive system. We confronted literature estimations of their feeding requirements with forage availability and quality, observed in three South African savannah systems, through linear modelling. The model predicted the proportion of below-canopy grass that grazers should include in their diet to meet their nutritional requirements.During the wet season, the model predicted that all animals could satisfy their daily nutrient requirements when feeding on a combination of below- and outside-canopy grasses. However, wildebeest, having relatively high nutrient demands, could meet their nutrient requirements only by feeding almost exclusively below canopies.During the dry season, all animals could gain almost twice as much digestible protein when feeding on below – compared to outside-canopy forage. Nonetheless, only warthogs could satisfy their nutrient requirements – when feeding almost exclusively on below-canopy grasses. The other ungulate species could not meet their phosphorus demands by feeding at either site without exceeding their maximum fibre intake, indicating the unfavourable conditions during the dry season.We conclude that grazing ungulates, particularly warthog, zebra, and buffalo, actually depend on the available below-canopy grass resources. Our model therefore helps to quantify the importance of higher quality forage patches beneath savannah trees. The composition of grazer communities depending on below-canopy grasses can be anticipated if grazer food requirements and the abundance of large trees in savannahs are known. The model suggests that the conservation of large single-standing trees in savannahs is crucial for maintenance of locally grazing herbivores.     

石鸡繁殖期栖息地的特征

2005年4~7月,对甘肃西部(东阿尔金山地区和西祁连山地区)和东南部(西秦岭地区)的石鸡(Alectoris chukar)种群栖息地选择进行了调查。主成分分析表明,草本密度、地面异质性和草本盖度是栖息地选择的主要影响因子;方差分析表明,甘肃西部(东阿尔金山和西祁连山)的石鸡种群在海拔、坡度和小石块数目的选择上差异显著。甘肃西部和东南部的石鸡种群在栖息地选择上存在显著的地理变异,西秦岭种群选择海拔低、坡度大、坡位偏上、草本密度低和草本高度高的栖息地。栖息地选择差异可能是在不同的选择压力下,经过长期的隔离进化形成。     

Termite mounds differ in their importance for herbivores across savanna types,seasons and spatial scales

Herbivores do not forage uniformly across landscapes, but select for patches of higher nutrition and lower predation risk. Macrotermes mounds contain higher concentrations of soil nutrients and support grasses of higher nutritional value than the surrounding savanna matrix, attracting mammalian grazers that preferentially forage on termite mound vegetation. However, little is known about the spatial extent of such termite influence on grazing patterns and how it might differ in time and space. We measured grazing intensity in three African savanna types differing in rainfall and foliar nutrients and predicted that the functional importance of mounds for grazing herbivores would increase as the difference in foliar nutrient levels between mound and savanna matrix grasses increases and the mounds become more attractive. We expected this to occur in nutrient‐poor areas and during the dry season when savanna matrix grass nutrient levels are lower. Tuft use and grass N and P content were measured along transects away from termite mounds, enabling calculation of the spatial extent of termite influence on mammalian grazing. Using termite mound densities estimated from airborne light detection and ranging (LiDAR), we further upscaled field‐based results to determine the percentage of the landscape influenced by termite activity. Grasses in close proximity to termite mounds were preferentially grazed at all sites and in both seasons, but the strength of mound influence varied between savanna types and seasons. In the wet season, mounds had a relatively larger effect on grazers at the landscape scale in the nutrient‐poor, wetter savanna, whereas in the dry season the pattern was reversed with more of the landscape influenced at the nutrient‐rich, driest site. Our results reveal that termite mounds enhance the value of savanna landscapes for herbivores, but that their functional importance varies across savanna types and seasons.     

Road mortality in freshwater turtles: identifying causes of spatial patterns to optimize road planning and mitigation

Road mortality of freshwater turtles can be high enough to imperil populations near roads, thus there is a need to efficiently and accurately locate regions of excessive road-kill along road networks for mitigation. Weekly over 2?years, we drove a 160?km highway circuit in northeastern New York State, USA and recorded the location of all detected road-kill of three freshwater turtle species (Chelydra serpentina, Chrysemys picta, Emydoidea blandingii). We then analyzed the spatial dispersion of road-kill and the road and landscape features associated with road-kill locations. Road-kill was most prevalent at a limited number of short road segments, termed ‘hotspots’. The locations of hotspots, as indicated by kernel density analysis, and the peak spatial extent of hotspots (250?m), as indicated by Ripley’s?K, corresponded to the locations and average lengths of causeways (road segments with wetlands within 100?m on both sides). Hotspots were located at causeways that were greater than 200?m length and characterized by high traffic volumes, close proximity to water, and high forest coverage. We conclude that freshwater turtle road mortality is spatially aggregated at short, severe hotspots, and hotspot locations can be predicted when the locations of wetlands, traffic volumes, and the land-uses bordering roads are known. Hotspot models using these predictors can locate sites along a road network that are the most promising for mitigation to reduce excessive road mortality and maintain connectivity.     

Effect of season of burning and removal of herbaceous cover on seedling emergence in a eucalypt savanna of north‐eastern Australia

Abstract Seedling emergence in a eucalypt savanna of north‐eastern Australia was documented over a 12‐month period, between May 1999 and May 2000. Seedling emergence for grasses, forbs and subshrubs was found to mainly occur in a brief pulse at the start of the wet season following fire or the removal of grass biomass. Only a minor number of tree and shrub seedlings were detected overall. Burning, or cutting away the grass layer in unburnt savanna, in both the early (i.e. May) and the late (i.e. October) dry seasons significantly increased seedling emergence over undisturbed savanna that had been unburnt for 3 years. Removing the grass layer in unburnt savanna, during either the early or the late dry season, triggered similar seedling densities to savanna burnt in the early dry season. Late dry season fires promoted the greatest seedling density. We attribute this to the higher intensity, late dry season fires releasing a greater proportion of seed from dormancy, coupled with the higher density of soil seed reserves present in the late dry season.     

Seasonal variation in the protein content and the grazing of some tropical savanna grasses

This paper presents the effects of seasonal variation on the protein contents of four grass species examined in the experimental fire plots at Kainji Lake National Park in the Northern Guinea savanna zone of Nigeria. Also reported is the proportion of grass utilized on year-long basis. Tropical savanna grasses generally have higher protein contents at the beginning of the growing season than at the end when they become tall, coarse and unpalatable. It is also shown that the percentage of grass species utilized by game follow the seasonal changes in their protein contents; utilization being highest when the protein content of grass is optimum. It is stressed that trees, shrubs and forbs should not be totally eliminated from grazing lands because of the great contribution they make to animal feeding during the dry season when the grasses become dry and coarse with low nutritive value.     

Resource partitioning along multiple niche dimensions in differently sized African savanna grazers

Resource partitioning among mammalian savanna herbivores is thought to be predominantly driven by differences in body size. In general, large herbivore species utilize abundant low quality forage while small herbivores focus on scarcer high quality food items. However, in a natural system other factors such as digestive strategy, season and the presence of megaherbivores (body size > 1000 kg) are likely to complicate allometric predictions. Non‐ruminants are probably better able to cope with abundant low quality food than ruminants of the same size causing a non‐ruminant to act ‘larger’ than allometrically predicted. Also, the effect of alternating seasons with high and low food availability on diet choice and hence the competitive interactions between co‐occurring herbivores is still poorly understood. Lastly, how megaherbivores deviate from allometric predictions (based on smaller species) is still not well quantified. In this study we examine resource partitioning among three ruminant and three non‐ruminant grazers: impala, wildebeest, buffalo, warthog, zebra and white rhinoceros (megaherbivore) in the savanna of Hluhluwe iMfolozi Park, South Africa. We analysed habitat and diet overlap, specifically grass species (something not commonly investigated) and grass height eaten, in both the wet and the dry seasons. We found that habitat utilization differences among the species were generally small and did not vary between seasons. Diets within feeding patches overlapped during the wet season but highly diverged during the dry season. Body mass differences among species explained their dry season resource partitioning for all species except for comparisons with the megaherbivore (white rhino), while differences in digestive strategy were not related to niche overlap in either season. We conclude that savanna herbivores in this system coexist mostly through body size‐driven resource partitioning in the dry‐season, with the exception of the white rhino (megaherbivore).     

Radio‐tracking three Sugar Gliders using forested highway median strips at Bongil Bongil National Park,north‐east New South Wales

Major roads and highways disrupt ecological flows and create barriers or filters to the movement of many species of wildlife, including gliding mammals. Mitigating these impacts presents major challenges for road authorities. One approach has been the retention of forest vegetation in median strips to serve as ‘stepping stones’ for gliding mammals to cross road gaps otherwise beyond their glide capacity. A recently upgraded section of the Pacific Highway through tall open forest near Bonville in north‐east New South Wales retained forest within two 10‐ to 45‐m‐wide median strips separating each carriageway and a service road. We investigated whether Sugar Gliders (Petaurus breviceps) used these median strips to cross an 85 to 135 m‐wide road corridor. Three radio‐collared Sugar Gliders (one male and two females) moved between both highway medians and forest on either side of the road corridor during 32 days of radio‐tracking. Although the sample size is small, these results suggest that highway median strips, featuring mature vegetation with a major den tree, can provide ‘stepping stones’ for gliding mammals to cross a highway that would otherwise function as a movement barrier or filter. Longer‐term research with greater numbers of animals at this and other sites is required to determine whether such strips would be commonly used when den trees are absent and whether gliding via median strips may also increase road mortality of the species.     

Landscape-scale feeding patterns of African elephant inferred from carbon isotope analysis of feces

The African elephant (Loxodonta africana) is a large-bodied, generalist herbivore that eats both browse and grass. The proportions of browse and grass consumed are largely expected to reflect the relative availability of these resources. We investigated variations in browse (C(3) biomass) and grass (C(4)) intake of the African elephant across seasons and habitats by stable carbon isotope analysis of elephant feces collected from Kruger National Park, South Africa. The results reflect a shift in diet from higher C(4) grass intake during wet season months to more C(3) browse-dominated diets in the dry season. Seasonal trends were correlated with changes in rainfall and with nitrogen (%N) content of available grasses, supporting predictions that grass is favored when its availability and nutritional value increase. However, switches to dry season browsing were significantly smaller in woodland and grassland habitats where tree communities are dominated by mopane (Colophospermum mopane), suggesting that grasses were favored here even in the dry season. Regional differences in diet did not reflect differences in grass biomass, tree density, or canopy cover. There was a consistent relationship between %C(4) intake and tree species diversity, implying that extensive browsing is avoided in habitats characterized by low tree species diversity and strong dominance patterns, i.e., mopane-dominated habitats. Although mopane is known to be a preferred species, maintaining dietary diversity appears to be a constraint to elephants, which they can overcome by supplementing their diets with less abundant resources (dry season grass). Such variations in feeding behavior likely influence the degree of impact on plant communities and can therefore provide key information for managing elephants over large, spatially diverse, areas.     

Factors affecting the distribution patterns of zebra and wildebeest in a resource-stressed environment

Understanding the spatial dynamics of landscape use by free-ranging herbivores is integral for successful ecosystem management. We used binary logistic regression analyses to determine the relative importance of biotic, abiotic and human factors in influencing the distribution (presence/absence) of wild grazers on two Maasai ranches in Kenya's Amboseli-Tsavo ecosystem. Both ranches had low grass biomass and suffered from regular droughts. We found that grazers consistently located themselves where grass biomass was highest, usually irrespective of grass quality, suggesting that forage quantity may be the limiting factor where grass biomass is generally low. The availability of surface water had no significant effect on the likelihood of grazers being present, even in the dry season.     

PAH contamination in road dust from a moderate city in North China: The significant role of traffic emission

To investigate the contamination level, distribution, possible source, and human exposure risk of polycyclic aromatic hydrocarbons (PAHs) in the urban traffic environment, 15 PAHs were measured in 34 road dust samples (particle size < 25 μm) collected from three grades of roads and park paths in Xinxiang, China. ΣPAHs concentrations ranged from 311 to 21200 ng g^?1, with a mean of 5890 ng g^?1 and decreased in the following order: main roads (7650 ng g^?1) > collector streets (7410 ng g^?1) > bypasses (2970 ng g^?1) > park paths (1570 ng g^?1), indicating that significant positive correlation existed between PAH contamination and traffic density. PAHs in all samples were dominantly composed of 4-ring PAHs, accounting for 44.8% of the total. Pyrene, fluoranthene, and chrysene were the predominant individual components and accounted for 14.7% (1.2–19.2%), 12.9% (3.3–20.3%), and 11.0% (2.5–18.6%) of ΣPAHs, respectively. The specific isomer ratios indicated that traffic emission was the dominant source of PAHs in road dust. The incremental lifetime cancer risk values showed that cancer risk from exposure to road dust–borne PAHs was acceptable for local residents in Xinxiang.     

The contribution of grazing to plant diversity in alpine grassland and heath

Abstract Grazing on transplants of a grass, a forb and a tree was examined in low-diversity grassland and more diverse heath in Australia's Snowy Mountains. Transplants were surrounded by 2 mm mesh netting. In one grassland plot, grazers (probably soil invertebrates) attacked 40–90% of tree and forb seedlings but no grass seedlings. In heath, which had about half the grass cover of grassland, grazers consumed grasses but not trees or forbs. The results suggest that grazers can depress diversity in grassland by attacking species other than grass. In heath, they may promote diversity by attacking only grass and releasing other species from competition.     

Food selection and competition in the East African buffalo (Syncerus caffer Sparrman)

Rumen samples collected at different times of the year from buffalo in the Serengeti, were analysed with respect to proportions of plant parts present. Buffalo were almost exclusive grazers and were capable of selecting for grass leaf. At certain times of year it was the dominant food intake component but declined to only 11% of the diet by the end of the dry season. The amount of leaf in the diet was determined by the amount of rainfall which governed the growth of the food grasses. Experimental preference tests with tame animals indicated that they were capable of selecting for different grass species. The preferences were, however, for those species with a higher leaf: stem ratio. The mechanism of selection is discussed. The function of the behavioural selection appeared to be concerned with maximizing the nutrient quality of the food requirements. It appeared that ecological separation had evolved through interspecific competition.     

Effects of roads on brown bear movements and mortality in Slovakia

The increasing development of road infrastructure considerably contributes to bear habitat fragmentation. The aim of this study was to examine the relationship between brown bear movements and secondary roads. The 1463-km² study area in the north-central Slovakia was defined by the composite home ranges (minimum convex polygon (MCP) 100%) of 21 bears studied by GPS telemetry from 2008 to 2016. Additionally, we used the data of 35 bears struck by cars and trucks across all of Slovakia during 2007–2015. We found that a traffic volume exceeding 5000 vehicles per 24 h completely restricted the movement of bears. Bears were more likely to cross during periods of low- rather than high-traffic volumes, and crossings occurred primarily at night. Males were able to cross roads with annual average daily traffic up to 5000 vehicles per 24 h, whereas females were only able to cross roads with less than 4000 vehicles per 24 h. Bears, regardless of age and gender, crossed roads more frequently during hyperphagia (August to November) than during the mating season (April to July). This was additionally confirmed by the comparison of annual patterns of crossings and road kills, which both peaked in August. The movement of these bears across roads was particularly motivated by the search for attractive crops in fields. Road crossings and road kills mainly occurred around midnight. Understanding the temporal and spatial use of roads by brown bears should provide valuable information for land use planners to effectively minimise the negative impacts of roads on bears.     

秦岭地区大熊猫种群空间利用消长状态以及道路影响研究

研究大熊猫种群空间利用的消长动态及其干扰因素对识别大熊猫潜在生境、保护大熊猫种群可持续增长具有重要的现实意义。本文收集了第三次和第四次秦岭大熊猫种群及栖息地调查数据,借助地理信息系统空间分析工具,对比分析了大熊猫种群的空间利用变化格局,并探究了道路干扰对大熊猫种群空间利用格局的影响。结果显示：（1）2000-2012年间,佛坪、长青核心密集区大熊猫种群空间利用密度西北方向增加,东南方向减少,即黄柏塬保护区呈增加趋势,而佛坪、观音山和周至保护区交界处呈减少趋势。其中,局部高密度区面积减少,但整体空间利用面积增大,并呈向外围扩散趋势。种群空间利用密度最大增长达3.05痕迹点/ km²,最大减小密度达2.71痕迹点/km²。（2）距国道、省道和县道2000 m以内种群空间利用密度增幅上升,距乡村道路2000 m外种群空间利用密度变化减小,且距高速公路3500 m大熊猫种群空间利用密度由减转增。深入探讨大熊猫种群空间利用格局可为建设优良栖息地和潜在栖息地提供参考,其结论将有助于优化道路选址和保护区规划,缓解人为活动和野生动物之间的冲突。     

Contemporary landscape burning patterns in the far North Kimberley region of north-west Australia: human influences and environmental determinants

Aim This study of contemporary landscape burning patterns in the North Kimberley aims to determine the relative influences of environmental factors and compare the management regimes occurring on Aboriginal lands, pastoral leases, national park and crown land. Location The study area is defined at the largest scale by Landsat Scene 108–70 that covers a total land area of 23,134 km² in the North Kimberley Bioregion of north‐west Australia, including the settlement of Kalumburu, coastline between Vansittart Bay in the west and the mouth of the Berkeley River in the east, and stretching approximately 200 km inland. Methods Two approaches are applied. First, a 10‐year fire history (1990–1999) derived from previous study of satellite (Landsat‐MSS) remote sensing imagery is analysed for broad regional patterns. And secondly, a 2‐year ground‐based survey of burning along major access roads leading to an Aboriginal community is used to show fine‐scale burning patterns. anova and multiple regression analyses are used to determine the influence of year, season, geology, tenure, distance from road and distance from settlement on fire patterns. Results Satellite data indicated that an average of 30.8% (±4.4% SEM) of the study area was burnt each year with considerable variability between years. Approximately 56% of the study area was burnt on three or more occasions over the 10‐year period. A slightly higher proportion of burning occurred on average in the late dry season (17.2 ± 3.6%), compared with the early dry season (13.6 ± 3.3%). The highest fire frequency occurred on basalt substrates, on pastoral tenures, and at distances 5–25 km from roads. Three‐way anova demonstrated that geological substrate and land use were the most significant factors influencing fire history, however a range of smaller interactions were also significant. Analysis of road transects, originating from an Aboriginal settlement, showed that the timing of fire and geology type were the most significant factors affecting the pattern of area burnt. Of the total transect area, 28.3 ± 2.9% was burnt annually with peaks in burning occurring into the dry season months of June, August and September. Basalt uplands (81.2%) and lowlands (30.1%) had greater areas burnt than sandstone (12.3%) and sands (17.7%). Main conclusions Anthropogenic firing is constrained by two major environmental determinants; climate and substrate. Seasonal peaks in burning activity in both the early and late dry season relate to periods of optimal fire‐weather conditions. Substrate factors (geology, soils and physiognomy) influence vegetation‐fuel characteristics and the movement of fire in the landscape. Basalt hills overwhelmingly supported the most frequent wildfire regime in the study region because of their undulating topography and relatively fertile soils that support perennial grasslands. Within these spatial and temporal constraints people significantly influenced the frequency and extent of fire in the North Kimberley thus tenure type and associated land uses had a significant influence on fire patterning. Burning activity is high on pastoral lands and along roads and tracks on some tenure types. While the state government uses aerial control burning and legislation to try to restrict burning to the early dry season across all geology types, in practice burning is being conducted across the full duration of the dry season with early dry season burning focused on sandstone and sand substrates and late dry season burning focused on basalt substrates. There is greater seasonal and spatial variation in burning patterns on landscapes managed by Aboriginal people.     

The effect of drought on the large mammal populations of Zambezi riverine woodlands

Large mammals were counted in Zambezi alluvial woodlands and on the adjacent ecotone in the north of Mana Pools National Park, Zimbabwe, from April 1981 until October 1989. Densities of all large herbivores on the alluvium in the daytime increased during the dry season. Year-to-year variation was studied by comparing end-of-dry-season densities. Flooding of the Zambezi River, controlled by Kariba Dam 100 km upstream, ceased in 1981 and the densities of all species on the alluvium declined in 1982. Rainfall was low in 1982 and very low in 1983 and 1984. The density of buffalo in the study area declined, owing to high mortality and a change in habitat utilization (buffalo herds spent more time in the south of the park). Densities of other species were high during the drought, but the densities of waterbuck, kudu, eland, bushbuck and warthog declined in 1985. Zebra density declined on the ecotone, but not on the alluvium. The densities of eland and kudu increased in 1986 and 1988, respectively, but the densities of the other species were still low in 1989. Impala density on the alluvium in October was related to rainfall during the preceding wet season and was high in drought years. Elephant density declined after a management cull. Rhinoceros density decreased by > 90% during the 1985/6 wet season, as a result of poaching and captures. The long-term decline in the densities of grazers was probably due primarily to the cessation of flooding by the Zambezi River, rather than to low local rainfall in some years. During the drought, the large grazers (e.g. buffalo) died before the smaller grazers (e.g. warthog). Waterbuck density declined less than the density of other grazers, because waterbuck could cross to vegetated sandbanks in the Zambezi River.     

Survey of the Influence of the Width of Urban Branch Roads on the Meeting of Two-Way Vehicle Flows

Branch roads, which are densely distributed in cities, allow for the flow of local traffic and provide connections between the city and outlying areas. Branch roads are typically narrow, and two-way traffic flows on branch roads are thus affected when vehicles traveling in opposite directions meet. This study investigates the changes in the velocities of vehicles when they meet on two-way branch roads. Various widths of branch roads were selected, and their influence on traffic flows was investigated via a video survey. The results show that, depending on the average vehicle velocity, branch roads require different widths to prevent a large decrease in velocity when vehicles meet. When the velocity on a branch road is not high (e.g., the average velocity without meeting is approximately 6 m/s), appropriately increasing the road width will notably increase the meeting velocity. However, when the velocity is high (e.g., the average velocity without meeting is greater than 10 m/s), there is a large decrease in velocity when meeting even if the road surface is wide (6.5 m). This study provides a basis for selecting the width of urban branch roads and the simulation of bidirectional traffic on such roads.     

Nutrient concentrations in two savannah grass species and their implications for grazers

The diversity of grazers on savannahs exerts pressure on the grass to provide nutrition. In this study the concentrations of major and trace animal nutrients in above ground grass tissue as influenced by grazing were examined. Two palatable grass species grazed by both livestock and wild grazers were sampled: Brachiaria nigropedata and Eragrostis lehmanniana. Samples of grass tissue were collected from widely spread sampling sites in both livestock and wildlife grazing sites, at the end of the growing season. Although B. nigropedata had higher nutrient concentrations, there was general covariance in nutrient levels in the two grasses. The covariance indicated that the respective sites generally had location context-dependent low or high nutrient concentrations in all grasses. The adequacy of the nutrient concentrations for grazer nutrition was assessed using literature-sourced minimum and maximum tolerable limit requirements of cattle and the high population gazelle-like species as illustration. The results showed that, in these nitrogen-limited savannahs, the grass generally met grazer requirements in terms of crude protein, potassium, molybdenum, nickel and zinc but that it had deficiencies in phosphorous, sodium, and boron, as well as grazing intensity-related localised toxic levels of potassium, phosphorous, magnesium, iron and manganese. The deficiencies and toxicities were inferred to result in abnormalities in grazer physical condition and reproduction. Given the importance of livestock in semiarid savannahs, these effects on livestock grazers were inferred as threatening human food security. The study shows that high grazing intensity can raise the concentrations of some animal nutrients in above ground grass tissue to levels above grazer tolerable limits. Grazing rotation to reduce grazing intensity is recommended as a proactive grazing management strategy to limit the effects.