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We outline how principles of optimal foraging developed for diet and food patch selection might be applied to movement behaviour expressed over larger spatial and temporal scales. Our focus is on large mammalian herbivores, capable of carrying global positioning system (GPS) collars operating through the seasonal cycle and dependent on vegetation resources that are fixed in space but seasonally variable in availability and nutritional value. The concept of intermittent movement leads to the recognition of distinct movement modes over a hierarchy of spatio-temporal scales. Over larger scales, periods with relatively low displacement may indicate settlement within foraging areas, habitat units or seasonal ranges. Directed movements connect these patches or places used for other activities. Selection is expressed by switches in movement mode and the intensity of utilization by the settlement period relative to the area covered. The type of benefit obtained during settlement periods may be inferred from movement patterns, local environmental features, or the diel activity schedule. Rates of movement indicate changing costs in time and energy over the seasonal cycle, between years and among regions. GPS telemetry potentially enables large-scale movement responses to changing environmental conditions to be linked to population performance.

Summary 1.Size relationships are central in structuring trophic linkages within food webs, leading to suggestions that the dietary niche of smaller carnivores is nested within that of larger species. However, past analyses have not taken into account the differing selection shown by carnivores for specific size ranges of prey, nor the extent to which the greater carcass mass of larger prey outweighs the greater numerical representation of smaller prey species in the predator diet. Furthermore, the top-down impact that predation has on prey abundance cannot be assessed simply in terms of the number of predator species involved. 2. Records of found carcasses and cause of death assembled over 46 years in the Kruger National Park, South Africa, corrected for under-recording of smaller species, enabled a definitive assessment of size relationships between large mammalian carnivores and their ungulate prey. Five carnivore species were considered, including lion ( Panthera leo ), leopard ( Panthera pardus ), cheetah ( Acinonyx jubatus ), African wild dog ( Lycaon pictus ) and spotted hyena ( Crocuta crocuta ), and 22 herbivore prey species larger than 10 kg in adult body mass. 3. These carnivores selectively favoured prey species approximately half to twice their mass, within a total prey size range from an order of magnitude below to an order of magnitude above the body mass of the predator. The three smallest carnivores, i.e. leopard, cheetah and wild dog, showed high similarity in prey species favoured. Despite overlap in prey size range, each carnivore showed a distinct dietary preference. 4. Almost all mortality was through the agency of a predator for ungulate species up to the size of a giraffe (800 -1200 kg). Ungulates larger than twice the mass of the predator contributed substantially to the dietary intake of lions, despite the low proportional mortality inflicted by predation on these species. Only for megaherbivores substantially exceeding 1000 kg in adult body mass did predation become a negligible cause of mortality. 5. Hence, the relative size of predators and prey had a pervasive structuring influence on biomass fluxes within this large-mammal food web. Nevertheless, the large carnivore assemblage was dominated overwhelmingly by the largest predator, which contributed the major share of animals killed across a wide size range.

Plant thorns and spines had these effects on the feeding behaviour of the three species of browsing ungulate that we studied, kudu, impala and domestic goats: (i) bite sizes were restricted, in most cases to single leaves or leaf clusters; (ii) hooked thorns retarded biting rates; (iii) the acceptability of those plant species offering small leaf size in conjunction with prickles was lower, at least for the kudus, than those of other palatable plant species; (iv) the inhibitory effect of prickles on feeding was much less for the smaller impalas and goats than for the larger kudus; (v) from certain hook-thorned species the kudus bit off shoot ends despite their prickles; (vi) for certain straight-thorned species the kudus compensated partially for the slow eating rates obtained by extending their feeding durations per encounter. Most spinescent species were similar in their acceptability to the ungulates to unarmed palatable species, despite higher crude protein contents in their foliage than the latter. Such structural features furthermore reduce the tissue losses incurred by plants per encounter by a large ungulate herbivore, by restricting the eating rates that the animals obtain. In this way prickles function to restrict foliage losses to large herbivores below the levels that might otherwise occur.

Citation: Pereira, L. ORCID: 0000-0002-4996-7234, Owen-Smith, N. and Moleon, M. (2013). Facultative predation and scavenging by mammalian carnivores: seasonal, regional and intra-guild comparisons. Mammal review, 44(1), pp. 44-55. doi: 10.1111/mam.12005 This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent

The importance of facilitation versus competition in structuring herbivore species assemblages is a critical issue in theoretical ecology as well as for practical wildlife management. This paper examines the evidence for facilitation and clarifies our understanding in relation to the mechanisms and the spatial and temporal scales where they occur. Evidence for facilitation through stimulation of grass regrowth during the growing season appears stronger than that for increased resource access through removal of obstructing grass structures during the dormant season. Although facilitation may benefit the nutritional gains obtained by certain species in the short term, these benefits do not appear to be translated into the expected population consequences. We suggest this could be due to seasonal tradeoffs between facilitation and competition, as well as to restrictions on the spatial extent of trophic overlap.

Grazing lawns are a distinct grassland community type, characterised by short-stature and with their persistence and spread promoted by grazing. In Africa, they reveal a long co-evolutionary history of grasses and large mammal grazers. The attractiveness to grazers of a low-biomass sward lies in the relatively high quality of forage, largely due to the low proportion of stem material in the sward; this encourages repeat grazing that concomitantly suppresses tall-grass growth forms that would otherwise outcompete lawn species for light. Regular grazing that prevents shading and maintains sward quality is thus the cornerstone of grazing lawn dynamics. The strong interplay between abiotic conditions and disturbance factors, which are central to grazing lawn existence, can also cause these systems to be highly dynamic. Here we identify differences in growth form among grazing lawn grass species, and assess how compositional differences among lawn types, as well as environmental variables, influence their maintenance requirements (i.e. grazing frequency) and vulnerability to degradation. We also make a clear distinction between the processes of lawn establishment and lawn maintenance. Rainfall, soil nutrient status, grazer community composition and fire regime have strong and interactive influences on both processes. However, factors that concentrate grazing pressure (e.g. nutrient hotspots and sodic sites) have more bearing on where lawns establish. Similarly, we discuss the relevance of enhanced rates of nitrogen cycling and of sodium levels to lawn maintenance. Grazer community composition and density has considerable significance to grazing lawn dynamics; not all grazers are adapted to foraging on short-grass swards, and differences in body size and relative mouth dimensions determine which species are able to convert tall-grass swards into grazing lawns under different conditions. Hence, we evaluate the roles of different grazers in lawn dynamics, as well as the benefits that grazer populations derive from having access to grazing lawns. The effects of grazing lawns can extend well beyond their borders, due to their influence on grazer densities, behaviour and movements as well as fire spread, intensity and frequency. Variation in the area and proportion of a landscape that is grazing lawn can thus have a profound impact on system dynamics. We provide a conceptual model that summarises grazing lawn dynamics, and identify a rainfall range where we predict grazing lawns to be most prevalent. We also examine the biodiversity associated with grazing lawn systems, and consider their functional contribution to the conservation of this biodiversity. Finally, we assess the utility of grazing lawns as a resource in a rangeland context.

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 antipoaching 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.