Search

Southern Africa is expected to experience increased frequency and intensity of droughts through climate change, which will adversely affect mammalian herbivores. Using bio-loggers, we tested the expectation that wildebeest (Connochaetes taurinus), a grazer with high water-dependence, would be more sensitive to drought conditions than the arid-adapted gemsbok (Oryx gazella gazella). The study, conducted in the Kalahari, encompassed two hot-dry seasons with similar ambient temperatures but differing rainfall patterns during the preceding wet season. In the drier year both ungulates selected similar cooler microclimates, but wildebeest travelled larger distances than gemsbok, presumably in search of water. Body temperatures in both species reached lower daily minimums and higher daily maximums in the drier season but daily fluctuations were wider in wildebeest than in gemsbok. Lower daily minimum body temperatures displayed by wildebeest suggest that wildebeest were under greater nutritional stress than gemsbok. Moving large distances when water is scarce may have compromised the energy balance of the water dependent wildebeest, a trade-off likely to be exacerbated with future climate change. [ABSTRACT FROM AUTHOR]

Nearly 90% of the world's large herbivore diversity occurs in Africa, yet there is a striking dearth of information on the movement ecology of these organisms compared to herbivores living in higher latitude ecosystems.The environmental context for movements of large herbivores in African savanna ecosystems has several distinguishing features. African large herbivores move in landscapes with high spatiotemporal variability, low predictability, seasonal restrictions in surface water as well as food resources, and exposure to a diverse assemblage of competitors, predators, and pathogens. These features influence mobility, diel activity routines, home‐range fidelity, and exposure to predation.We review the knowledge that has been gained about the movements of African herbivores from Global Positioning System (GPS) telemetry and identify important gaps in knowledge that exist. Topics addressed include seasonal movement patterns, daily activity schedules, space utilisation, water dependency, responses to risks of predation, pathogen transmission, social affiliations, and local population density determination.While the growing number of GPS telemetry studies has addressed a wide range of topics in Africa, they remain fragmentary in terms of places and species represented. Most research has been focussed on three species, and practices for data sharing and analysis should be improved. African landscapes are changing perhaps faster than any other region on Earth, with rapidly expanding human populations, massive infrastructure development projects, and changes in climatic regimes. There is a crucial need to establish relationships between herbivore movements and their changing environments, especially in Africa where most of the world's large herbivore diversity resides. [ABSTRACT FROM AUTHOR]

Climate and land use change modify surface water availability in African savannas. Surface water is a key resource for both wildlife and livestock and its spatial and temporal distribution is important for understanding the composition of large herbivore assemblages in savannas. Yet, the extent to which ungulate species differ in their water requirements remains poorly quantified. Here, we infer the water requirements of 48 African ungulates by combining six different functional traits related to physiological adaptations to reduce water loss, namely minimum dung moisture, relative dung pellet size, relative surface area of the distal colon, urine osmolality, relative medullary thickness, and evaporation rate. In addition, we investigated how these differences in water requirements relate to differences in dietary water intake. We observed strong correlations between traits related to water loss through dung, urine and evaporation, suggesting that ungulates minimize water loss through multiple pathways simultaneously, which suggests that each trait can thus be used independently to predict water requirements. Furthermore, we found that browsers and grazers had similar water requirements, but browsers are expected to be less dependent on surface water because they acquire more water through their diet. We conclude that these key functional traits are a useful way to determine differences in water requirements and an important tool for predicting changes in herbivore community assembly resulting from changes in surface water availability. [ABSTRACT FROM AUTHOR]

Abstract Impacts of predators on prey populations are incurred not only through mortality inflicted, but also from how the risk of mortality affects the behaviour, spatial distribution and resource access of potential prey species. This risk is governed by exposure to predators and vulnerability following encounters. Behavioural responses to reduce risks have ramifying consequences for habitat partitioning, regional distributions and local impacts of herbivores on vegetation. These consequences are reviewed for carnivore-ungulate assemblages in African savanna ecosystems. Vigilance serves multiple functions, including locating food and maintaining group cohesion as well as detecting predators. Prey responses depend on whether predators hunt by ambush or pursuit and whether they are mainly diurnally or nocturnally active. Ungulates can lower their vulnerability by restricting time spent foraging at night and avoid places providing cover for lurking carnivores. Risks of predation can have a stronger influence on spatial partitioning among large grazers than distinctions in resource use. Only species above some threshold size have distributions indifferent to tree and grass cover. Observed mortality rates are constrained by recruitment potential. Spatiotemporal variation in risk may regulate populations and limit regional abundance. Herbivores confined to secure habitat may generate local brown-green-black world mosaics. Less common prey species of greatest conservation concern are most susceptible to having their habitat security breached by changes in predation risk. Studies establishing baseline responses of ungulates to the risk of predation need to be augmented by investigations focussed on extreme situations. Highlights • Prey respond to the risk of predation influence spatial partitioning, regional distributions and vegetation impacts • Vigilance serves multiple functions, including herd cohesion and locating food as well as predator detection • Prey activity differs at night when ambush predators hunt most actively • Risk of predation can have a stronger influence on spatial partitioning among large grazers than distinctions in resource use. • It is the less common ungulates of greatest conservation concern that are most susceptible to having their habitat security breached by elevated predation [ABSTRACT FROM AUTHOR]

Ungulates inhabiting high latitudes schedule the timing of conceptions so that offspring are born during the most favourable nutritional conditions for reproductive success. The optimal period for births is less reliably predictable in tropical and subtropical savanna environments where plant growth is governed by rainfall, suggesting that reproductive phenology could be influenced more proximately by resources affecting the body condition of females around the time of conceptions. To assess how these controls operate, we compared the timing of births and conceptions among tropical and subtropical savanna ungulates with the patterns shown by ungulates in northern temperate or subarctic latitudes. The association between the timing of births and the onset of plant growth early in the growing season is less consistent among tropical savanna ungulates than among ungulates inhabiting northern temperate environments, and apparently subject to other influences affecting vegetation phenology. Nevertheless, birth peaks seem to coincide with the time of the year when forage quality is expected to be best for offspring survival and growth for most tropical or subtropical ungulates with gestation periods shorter than a year. When gestation time exceeds one year, proximal effects of nutritional conditions around the time of conceptions apparently become overriding and birth synchrony with early season plant growth is no longer effective. Proximate nutritional influences on conceptions may also govern the somewhat diffuse spread of births shown by ungulate populations in equatorial latitudes where photoperiod cues controlling oestrus and mating cannot be used to schedule the later timing of births. [ABSTRACT FROM AUTHOR]

Abstract: Large predators have been reintroduced to an increasing number of protected areas in South Africa. However, the conditions allowing both prey and predator populations to be sustained in enclosed areas are still unclear as there is a lack of understanding of the consequences of such reintroductions for ungulate population dynamics. Variation in lion numbers, two decades after their first release, offered a special opportunity to test the effects of predation pressure on the population dynamics of seven ungulate species in the 960 km2 Hluhluwe-iMfolozi Park (HiP), South Africa. We used two different approaches to examine predator–prey relationships: the population response of ungulates to predation pressure after accounting for possible confounding factors, and the pattern of ungulate adult mortality observed from carcass records. Rainfall patterns affected observed mortalities of several ungulate species in HiP. Although lion predation accounted for most ungulate mortality, it still had no detectable influence on ungulate population trends and mortality patterns, with one possible exception. This evidence suggests that the lion population had not yet attained the maximum abundance potentially supported by their ungulate prey; but following recent increases in lion numbers it will probably occur soon. It remains uncertain whether a quasi-stable balance will be reached between prey and predator populations, or whether favoured prey species will be depressed towards levels potentially generating oscillatory dynamics in this complex large mammal assemblage. We specifically recommend a continuous monitoring of predator and prey populations in HiP since lions are likely to show more impacts on their prey species in the next years. [Copyright &y& Elsevier]

We compared the grass height grazed by white rhino, wildebeest, zebra and impala through the dry season months in the Hluhluwe–iMfolozi Park in South Africa. We expected that the grass height grazed would increase with the body size of the herbivore species, as suggested from past studies of resource partitioning among large mammalian herbivores. Instead we found that the largest of these species, white rhino, concentrated on the shortest grass, while the smallest species, impala, grazed heights intermediate between those grazed by wildebeest and zebra. Results suggest that the scaling of mouth width relative to body size, and hence to metabolic demands, may be the primary factor governing grass height selection, rather than body size alone. This calls into question the widespread assumption that smaller herbivores are superior competitors through being able to persist on sparser vegetation. Furthermore, there was considerable overlap in grass height grazed among these four species, indicating that niche separation by grass height is inadequate alone to explain their coexistence. [ABSTRACT FROM AUTHOR]

Compares the use of grass regrowth following burns by ungulate species at the Nylsvley Nature Reserve in South Africa. Analysis on the relative distribution of ungulates between burnt and unburnt grassland using log-linear method; Concentration of roan antelope neat the river channel; Efforts of the herbivore species to compete for a food resource.