Norman Owen-Smith

Norman Owen-Smith
University of the Witwatersrand | wits · School of Animal, Plant and Environmental Sciences

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143
Publications
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Publications

Publications (143)
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Chapter
That humans originated from Africa is well-known. However, this is widely regarded as a chance outcome, dependant simply on where our common ancestor shared the land with where the great apes lived. This volume builds on from the 'Out of Africa' theory, and takes the view that it is only in Africa that the evolutionary transitions from a forest-inh...
Article
Competition with livestock over forage resources has been identified as a potential threat to the survival of the African wild ass (Equus africanus) in the Danakil ecosystem (Eritrea). The Messir Plateau is an important breeding area for the African wild ass but also hosts cattle, sheep, goats, donkeys, and camels. Locations and fecal samples of Af...
Article
Full-text available
Migration of ungulates (hooved mammals) is a fundamental ecological process that promotes abundant herds, whose effects cascade up and down terrestrial food webs. Migratory ungulates provide the prey base that maintains large carnivore and scavenger populations and underpins terrestrial biodiversity (fig. S1). When ungulates move in large aggregati...
Article
Full-text available
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-adapt...
Article
The critically endangered African wild ass (Equus africanus) occurs in the Danakil Desert of Eritrea and Ethiopia. Drinking behaviour and the costs of accessing water are critical to understanding how this threatened equid survives in an arid environment. Drinking data and distance travelled to water of 24 females and five males were recorded for 8...
Article
• 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....
Article
Full-text available
Concern for megafauna is increasing among scientists and non-scientists. Many studies have emphasized that megafauna play prominent ecological roles and provide important ecosystem services to humanity. But, what precisely are ‘megafauna’? Here, we critically assess the concept of megafauna and propose a goal-oriented framework for megafaunal resea...
Article
Full-text available
Large mammals respond to seasonal changes in temperature and precipitation by behavioural and physiological flexibility. These responses are likely to differ between species with differing water dependencies. We used biologgers to contrast the seasonal differences in activity patterns, microclimate selection, distance to potential water source and...
Chapter
Elephants occupy a dietary niche distinct from that of smaller browsers by consuming fibrous bark and root tissues along with leaves. They have the capacity to directly induce plant mortality through toppling, pollarding, uprooting, or debarking woody plants. African elephants are recognized to be among the major drivers of the structure and compos...
Article
Abstract It is commonly assumed that larger species are more vulnerable to extinction because of their low population densities and slow time to recover from setbacks. We report that, contrary to this expectation, it is the smaller ungulate species that first reached the brink of local extirpation within a 950 km2 fenced protected area, the Hluhluw...
Article
Full-text available
For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this m...
Article
Full-text available
Space use patterns have generally been interpreted using home-range concepts without distinguishing the particular activities performed in different regions. The relative influences of food resources, security from predation and shelter from thermal extremes on space occupation are likely to vary with time of day and changing conditions over the se...
Chapter
Cambridge Core - Ecology and Conservation - Conserving Africa's Mega-Diversity in the Anthropocene - edited by Joris P. G. M. Cromsigt
Book
Centring on South Africa's Hluhluwe-iMfolozi Park, this book synthesizes a century of insights from the ecology and conservation management of one of Africa's oldest protected wildlife areas. The park provides important lessons for conservation management, as it has maintained conservation values rivalling those of much larger parks sometimes throu...
Article
The canalization hypothesis postulates that the rate at which trait variation generates variation in the average individual fitness in a population determines how buffered traits are against environmental and genetic factors. The ranking of a species on the slow-fast continuum - the covariation among life-history traits describing species-specific...
Article
Wildlife populations have been experiencing declines across western, central and eastern Africa. In Tanzania, a national wildlife policy was instituted in 1998 to increase protection of wildlife. We assessed (i) the extent to which large herbivore populations have continued to decline in density and distribution within three representative protecte...
Article
Full-text available
Prey mortality depends on the likelihood of encountering a predator and of being killed following such an encounter. While the proactive responses of large herbivores to the risk of predation have been well documented, the reactive responses of prey following encounters have been less well studied and restricted mostly to northern temperate ecosyst...
Article
Full-text available
Moon phase affects nocturnal activity patterns in mammals. Among ungulates, a number of studies have found animals to be more active over full moon nights. This may be because increased luminosity provides increased opportunity to forage and/or increased ability to detect predators; known as the visual acuity hypothesis. Here, we use GPS-derived mo...
Preprint
Full-text available
The impact that large mammalian carnivores can have on the abundance of their ungulate prey remains contentious and achieving scientific consensus has proved elusive. Several studies in temperate latitudes in North America have documented how increases in the abundance of wolves have been associated with declines in the abundance of certain large u...
Preprint
Full-text available
The impact that large mammalian carnivores can have on the abundance of their ungulate prey remains contentious and achieving scientific consensus has proved elusive. Several studies in temperate latitudes in North America have documented how increases in the abundance of wolves have been associated with declines in the abundance of certain large u...
Article
Full-text available
Niche separation among species with similar resource requirements can be expressed at various spatiotemporal scales, from the resource components selected at feeding sites to habitat and home range occupation and ultimately geographic distribution ranges. African large herbivores present a challenge to niche theory because multiple species commonly...
Article
Full-text available
In high temperate latitudes, ungulates generally give birth within a narrow time window when conditions are optimal for offspring survival in spring or early summer, and use changing photoperiod to time conceptions so as to anticipate these conditions. However, in low tropical latitudes day length variation is minimal, and rainfall variation makes...
Article
Sable antelope, Hippotragus niger, populations have declined substantially in Kruger National Park, South Africa despite large-area protection from land use and poaching. Since Africa's large mammal populations are restricted to protected areas, understanding how to manage parks for biological diversity is critically important to the sustainability...
Article
Full-text available
An intermediate spatiotemporal scale of food procurement by large herbivores is evident within annual or seasonal home ranges. It takes the form of settlement periods spanning several days or weeks during which foraging activity is confined to spatially discrete foraging arenas, separated by roaming interludes. Extended by areas occupied for other...
Article
Full-text available
A deterministic mathematical model of the black rhino population in South Africa will be discussed. The model is constructed by dividing the black rhino population into multiple patches. The impact of human intervention on different translocation strategies is incorporated into the model. It is shown that, when implemented correctly, translocation...
Article
Full-text available
Movement is a key mean for mobile species to cope with heterogeneous environments. While in herbivorous mammals large-scale migration has been widely investigated, fine-scale movement responses to local variations in resources and predation risk remain much less studied, especially in savannah environments. We developed a novel approach based on co...
Article
Full-text available
The particle size of the food resource strongly determines the structure and dynamics of food webs. However, the ecological implications of carcass size variation for scavenging networks structure and functioning have been largely overlooked. Here we investigate differences in scavenging patterns due to carcass size in a complex vertebrate scavenge...
Article
Differences in resource selection (i.e., habitat selection and diet composition) may allow for coexistence of interspecific competitors. Two congeneric floodplain antelope with broadly similar habitat use are puku (Kobus vardonii) and lechwe (K. leche). In Botswana, puku are restricted to a narrow band of floodplains along the Chobe River, whereas...
Conference Paper
Background/Question/Methods African savanna ecosystems commonly support five large mammalian carnivores along with 20 or more species of large herbivore. While body size distinctions structure the predator-prey linkages, explaining how these predators and their prey coexist requires understanding the interplay of demographic composition, seasonal...
Article
Full-text available
Since the origin of early Homo species during the Late Pliocene, interactions of humans with scavenging birds and mammals have changed in form through shifting ecological scenarios. How humans procured meat during the Quaternary Period changed from confrontational scavenging to hunting; shepherding of wild animals; and, eventually, intensive husban...
Article
Full-text available
The extent to which vertebrate carnivores shift facultatively between predation and scavenging has recently been emphasized. Potentially, all carnivores have to do is wait until animals succumb to the debilitating effects of advancing age. However, this may be insufficient because of intense competition among other scavengers and decomposers for fo...
Article
Animals that are relatively rare in local species assemblages are commonly assumed to be narrowly selective in their habitat or dietary requirements, with the latter generally assessed in terms of the range of food types consumed. We inves-tigated whether a narrow dietary range might help explain the restricted distribu-tion and low local densities...
Article
Full-text available
Knowledge of the success or otherwise of conservation interventions is often locked within localised networks, resulting in mistakes being replicated unnecessarily. The savannahs of eastern and southern Africa are home to spectacular ecosystems with similar ecology yet markedly different conservation practices between the two regions. Pressures on...
Article
In the Kruger National Park, sable antelope underwent a substantial decline in abundance after 1987. Our study investigated whether forage quality as reflected by faecal nutrient contents could be restricting population recovery. Faecal samples were collected from sable, zebra and buffalo in one study area and from sable only in a second study area...
Article
Full-text available
Diet-related disorders occur frequently in captive browsing ruminants. To assess current feeding practices, diets of 15 captive greater kudus (Tragelaphus strepsiceros) from three zoological collections were compared to that of free-ranging conspecifics and current feeding recommendations. Dry matter intake (DMI) varied considerably in captivity fr...
Article
Africa is renowned for the current abundance and diversity of its large mammals. The aim of this study was to assess distinctions evident in the functional composition of continental large herbivore faunas during the late Pleistocene before extinctions depleted the megafauna outside Africa. The African large herbivore fauna was compared with that f...
Article
Context. Daily movement responses could indicate food deficiencies threatening population persistence before consequences for population performance become manifested. Animals should respond to food deficiencies by spending less time in foraging areas and hence by moving more frequently between such areas between one day and the next. Aim. To estab...
Article
Full-text available
There has recently been a spate of manuscripts submitted to South African Journal of Wildlife Research that have lacked animal ethics approvals. Clearly this is a serious concern - not only from the chance that unethical research practices have occurred but also that there are no checks and balances to ensure this is the case. In several of those c...
Article
Although excessive iron storage in black rhinoceros (Diceros bicornis) has been a cause for continuous concern over the last four decades and differences in the iron content of diet items fed in captivity and in the wild have been documented, no reports exist on the iron content of the total diet ingested by free-ranging animals. Here, the results...
Article
Full-text available
Documenting current species distribution patterns and their association with habitat types is important as a basis for assessing future range shifts in response to climate change or other influences. We used the adaptive local convex hull (a-LoCoH) method to map distribution ranges of 12 ungulate species within the Kruger National Park (KNP) based...
Article
Full-text available
Species assemblages commonly include species persisting at low density alongside more abundant species, raising questions about the mechanisms enabling this coexistence. Relatively rare species may persist through (1) specializing on a narrow range of resource types that are sparsely but widely available or (2) precisely selecting patches where the...
Article
The metabolic rate—body size relationship suggests that the African elephant (Loxodonta africana) should be least selective among mammalian herbivores in its diet. However, selection among plant species needs to be distinguished from selection for plant parts or other features. We investigated seasonal variation in the selective utilization and die...
Article
Land use change and human population growth are accelerating the fragmentation and insularization of wildlife habitats worldwide. The conservation and management of wildlife in the resultant ‘island’ ecosystems in the context of global warming is challenging due to the isolation and reduced size of the ecosystems and hence the scale over which ecos...
Article
Context. To interpret spatial utilisation distributions, there is a need to translate animal locations obtained from global positioning system (GPS) telemetry into the activities performed and, hence, benefits derived, from particular places and times of day. Derived activity patterns also reveal how animals cope in changing environmental condition...
Article
Full-text available
Documenting current species distribution patterns and their association with habitat types is important as a basis for assessing future range shifts in response to climate change or other influences. We used the adaptive local convex hull (á-LoCoH) method to map distribution ranges of 12 ungulate species within the Kruger National Park (KNP) based...
Article
Full-text available
Sable antelope numbers in the Kruger National Park have declined substantially since the mid-1980s and have shown little recovery despite improved rainfall conditions. We used aerial survey records to investigate how changes in herd numbers, herd sizes, calf proportions and consequent changes in the distribution range of breeding herds contributed...
Article
Coexistence among grazing ungulates has been related to differences in grass height and grassland types selected, underlain by morphological distinctions. Nevertheless, resource competition may arise when smaller species depress grass height below that suitable for larger species, whereas competition may be counteracted by facilitation when larger...
Article
1. There is a pressing need for population models that can reliably predict responses to changing environmental conditions and diagnose the causes of variation in abundance in space as well as through time. In this ‘how to’ article, it is outlined how standard population models can be modified to accommodate environmental variation in a heuristical...
Article
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 live...
Data
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Supporting document Appendix S2. (0.07 MB PDF)
Data
Supporting document Appendix S1. (0.08 MB PDF)
Article
Full-text available
Background: The dominant paradigm for modeling the complexities of interacting populations and food webs is a system of coupled ordinary differential equations in which the state of each species, population, or functional trophic group is represented by an aggregated numbers-density or biomass-density variable. Here, using the metaphysiological ap...
Article
Full-text available
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 r...
Article
Full-text available
The decline of woodlands as a result of elephant disturbance is of much concern for biodiversity conservation in Africa. Northern Botswana supports the largest elephant (Loxodonta africana) population and highest local density levels near rivers during the dry season. We describe changes in structure and composition that have occurred in the ripari...
Chapter
Models of herbivore–vegetation interactionsExamples of irruptive dynamicsEffects of irruptions on vegetationChanging perspectivesSynthesisImplications for conservation and managementAcknowledgmentsReferences
Article
Burning is commonly used in savannas to stimulate grass regrowth for grazing ungulates. We recorded the relative use of burns occurring at different stages in the seasonal cycle, as well as in different regions of the landscape by two herds of sable. We also recorded behavioural measures of foraging efficiency and faecal nutrient contents as an ind...
Article
Full-text available
A resurvey of a sample of marula trees (n = 474) in the Kruger National Park (KNP) originally documented in 2001, was conducted in 2008 to determine the response of this population segment to the conditions prevalent during that time. These included an increasing elephant population and changes to the KNP fire policy. The overall mortality rate was...
Article
Elephants ( Loxodonta africana (Blumenbach 1797)) can have a major transforming effect on savanna structure through felling, debarking or uprooting trees (Dublin et al . 1990, Laws 1970, Mapaure & Campbell 2002). However, it is difficult to separate their influence from that of other causes of tree mortality, including wind storms (Spinage & Guinne...
Article
We use mechanistic arguments to generalize a hierarchical metaphysiological approach developed by one of us to modeling biological populations (Getz, [1991, 1993]) and extend the approach to include a storage component in the population. We model the growth of single species and consumer-resource interactions, both with and without storage. Our app...
Article
Shifting prey selection has been identified as a mechanism potentially regulating predator-prey interactions, but it may also lead to different outcomes, especially in more complex systems with multiple prey species available. We assessed changing prey selection by lions, the major predator for 12 large herbivore species in South Africa's Kruger Na...