Sam Ferreira

• PhD
• Large Mammal Ecologist at SANParks

Lions (Panthera leo) are declining across their range, mainly due to human‐induced habitat fragmentation and prey depletion. However, the South African lion population continues to grow. Unlike other range states, South Africa actively manages wild lions across a continuum of landscapes and ecological constraints. Many of these lions are in small,...

Climate change has massive global impacts and affects a wide range of species. Threatened species such as the roan antelope (Hippotragus equinus) are particularly vulnerable to these changes because of their ecological requirements. Attempts to address concerns about the roan's vulnerability have not been well documented in South African protected...

Species typically occupy fewer sites, and average population densities decline from the centre to the edge of a species’ range when the range contracts. The poaching of rhinoceroses (rhinos) for their horn has degraded the black and white rhino populations in Kruger National Park (Kruger). Rhino populations have declined, and their distributions ha...

Spatial patterns of and competition for resources by territorial carnivores are typically explained by two hypotheses: 1) the territorial defence hypothesis and 2) the searching efficiency hypothesis. According to the territorial defence hypothesis, when food resources are abundant, carnivore densities will be high and home ranges small. In additio...

Context Due to considerable declines in African wildlife populations, most large African mammals are managed inside protected areas. Protected areas come in various sizes, and have different environmental features, climates and management strategies (i.e. ‘hands-on’ or ‘hands-off’) that can influence an animals’ homeostasis. White rhinos (Ceratothe...

Harnessing the fear animals have of humans has the potential to aid in the conservation of wildlife. Most vertebrates perceive humans as “super predators.” While predator cues are an important nonlethal management tool, the use of human cues for management has rarely been implemented or experimentally tested. Extensive poaching is threatening the p...

Predator avoidance strategies vary across the ungulate guild. Population-level responses to the presence of large predators to a large extent depend on how well ecological conditions suit the particular predator avoidance strategies of a species. Predation risk from ambush predators, e.g. lions negatively correlates with distance from surface water...

African lion (Panthera leo) populations normally consist of several neighbouring prides and multiple adult males or groups of males that interact competitively. In large, open systems, cub defence from infanticidal males and territory defence drive group living in lions. However, in smaller (<1000 km²), fenced wildlife reserves, opportunities for n...

African lions (Panthera leo) and spotted hyaenas (Crocuta crocuta) play key roles in savanna ecosystems. Habitat change, overharvesting and retaliatory killing may threaten the persistence of some populations. Climate may cause further disturbance that accentuate negative effects. Droughts weaken the ability of prey to avoid predators resulting in...

The combined use of global positioning system (GPS) technology and motion sensors within the discipline of movement ecology has increased over recent years. This is particularly the case for instrumented wildlife, with many studies now opting to record parameters at high (infra-second) sampling frequencies. However, the detail with which GPS logger...

Background Understanding what animals do in time and space is important for a range of ecological questions, however accurate estimates of how animals use space is challenging. Within the use of animal-attached tags, radio telemetry (including the Global Positioning System, ‘GPS’) is typically used to verify an animal’s location periodically. Strai...

Global COVID-19 responses by governments restricted international travel, imposed national lockdowns, reduced economies, and influenced people's livelihoods. Travel restrictions and national lockdowns may constrain international illegal supply chains of high value wildlife products such as rhinoceros (rhino) horn. We evaluated whether the COVID-19...

Large herbivores, particularly in water limited systems, are vulnerable to the impacts of poaching (illegal hunting) and human‐induced climate changes. However, we have little understanding of how these processes can reshape their populations. With some rapidly declining populations there is a need to understand the effects of these stressors on po...

Rapid population growth of reintroduced lions (Panthera leo) poses several ecological and management challenges in small (

Background Fine-scale data on animal position are increasingly enabling us to understand the details of animal movement ecology and dead-reckoning, a technique integrating motion sensor-derived information on heading and speed, can be used to reconstruct fine-scale movement paths at sub-second resolution, irrespective of the environment. On its own...

The combined use of Global Positioning System (GPS) technology and motion sensors within the discipline of movement ecology has increased over recent years. This is particularly the case for instrumented wildlife, with many studies now opting to record parameters at high (infra-second) sampling frequency. However, the detail with which GPS loggers...

Background Understanding what animals do in time and space is important for a range of ecological questions, however accurate estimates of how animals use space is challenging. Within the use of animal-attached tags, radio telemetry (including the Global Positioning System (GPS)) is typically used to verify an animal’s location periodically. Straig...

The elephant population in the Kruger National Park (KNP) has been increasing since the cessation of culling in the mid-1990s. This contrasts with recent trends in elephant populations in many parts of Africa where poaching continues to decrease numbers. Logistic growth theory predicts that increased competition for vital resources when densities i...

Background Fine-scale data on animal position are increasingly enabling us to understand the details of animal movement ecology and dead-reckoning, a technique integrating motion sensor-derived information on heading and speed, can be used to reconstruct fine-scale movement paths at sub-second resolution, irrespective of the environment. On its own...

Conservation areas, like national parks, are hotspots of social-ecological and social-economic activities. The resulting interactions contribute to an inherent complexity of these systems, making simulation models a vital form of support for their management activities. These models are often unimodal, i.e., limited by design to only one particular...

The COVID-19 pandemic is a global crisis emanating both from a virus (SARS-CoV-2) and from the drastic actions to contain it. Here, we reflect on the immediate responses of most world powers amid the pandemic chaos: totalitarian surveillance and nationalist isolation. Drawing on published literature, we consider measures such as wildlife-use bans,...

Estimates of the numbers of living rhinoceroses inform management interventions. Several techniques assist authorities in obtaining estimates. For large populations, authorities use sample-based methods. Estimates for the number of rhinos living in Kruger National Park (Kruger) make use of sample-based block surveys. Critics of this approach allege...

The degree of relatedness and an interacting unifying central member can exacerbate disease transmission within a social group. The severity of the disease depends on the route, dose and frequency of infection. Group-living social mammals thus have the ability to exacerbate the spread of the disease. Lions Panthera leo are social carnivores with in...

Overharvesting affects the size and growth of wildlife populations and can impact population trajectories. Overharvesting can also severely alter population structure and may result in changes in spatial organisation, social dynamics and recruitment. Understanding the relationship between overharvesting and population growth is therefore crucial fo...

Prey biomass, diversity, and availability dictate predator abundances and niche structure. Increased prey biomass and availability predicts that two apex predators, African lions and spotted hyaenas, should increase in abundance. Although elephant and rhino carcasses generated by poachers released prey biomass not previously available, individual l...

The role of social cues in the reproduction of social mammals, particularly carnivores, has been thoroughly studied and documented in literature. However, environmental cues such as resources of water, food, and shelter have been identified to a lesser extent. Pregnant lions (Panthera leo) are notoriously secretive during the final stages of pregna...

Kenya's Tsavo National Parks are a critical conservation area and the only wilderness corridor through densely populated human‐dominated landscapes stretching from the East African coast to Lake Victoria, separating extensive undeveloped grasslands south of the equator from the undeveloped semiarid bushlands to the north. At nearly 21,000 km ² , Ts...

Changes in demographic features of the lion population in the south‐western Kgalagadi Transfrontier Park cause conservation concern. The ratio between adult males and females changed from 1♂:2♀ to 1♂:1♀ over a 32‐year period (1977–2010). This is atypical for undisturbed lion populations. We evaluated mechanisms that on their own or together could e...

The ecological functioning of an environment is influenced by how lions, Panthera leo, utilize their prey at various spatial and temporal scales. Aspects of the spatial and temporal variation in lion diet were investigated in the southwestern Kgalagadi Transfrontier Park (KTP) between May 2013 and June 2015 using evidence of prey remains identified...

Droughts are predicted to increase in frequency and intensity for large parts of Africa. It is unclear how this may impact native grazers in protected areas, and how these outcomes may differ under contrasting management approaches. Reducing artificial water sources and increasing the size of protected areas have been proposed as management respons...

The spatio-temporal distribution of forage and surface water shapes space-use for many herbivore species. Herbivores must make trade-offs between critical resources such as water and forage under resource-limited conditions. The species-specific strategy employed to do so, however, varies with nutritional requirements, thermoregulation and body siz...

Ecological traps occur when areas preferentially selected by a species harbour an unknown increased mortality risk or reduced fitness for the individuals utilizing them. If animals continue to utilize these habitats, rapid declines may result that threaten the persistence of the population. Both black and white rhinoceroses are plagued by severe, t...

Context Managed wild lions (Panthera leo) are lions found in smaller (<1000 km²), fenced protected areas that hold a substantial portion of South Africa’s wild lion population. Because the natural population control mechanisms are compromised within these properties, managers must actively control population growth rates. Fecundity control is used...

Understanding and identifying drivers of local population declines are important in mitigating future risks and optimising conservation efforts. The Knysna elephants have, after being afforded protection since the early 1900s, declined to near extinction today. We propose three hypotheses as to why the Knysna elephant population declined. The refug...

Conservation agencies rely on accurate wildlife population estimates to inform management practices. The importance of accuracy increases with smaller, threatened populations, but so too does the challenge in achieving it, especially for evasive species in low-visibility terrain. Non-invasive survey techniques have been successfully applied in such...

Unrelenting poaching to feed the illegal trafficking of rhinoceros (rhino) horn remains the principle threat to the persistence of south-central black and southern white rhino that live in the Kruger National Park (Kruger), South Africa. Other global environmental change drivers, such as unpredictable climatic conditions, impose additional uncertai...

Context Direct observations of animals are the most reliable way to define their behavioural characteristics; however, to obtain these observations is costly and often logistically challenging. GPS tracking allows finer-scale interpretation of animal responses by measuring movement patterns; however, the true behaviour of the animal during the peri...

The global conservation status of Nile crocodiles (Crocodylus niloticus) was last assessed in 1996. The species presents particular difficulty in monitoring because it can be cryptic, require expertise to handle, and caudal tail tags and transmitters are often lost. Some studies advocate mark-recapture techniques based on photograph identification...

Small populations are vulnerable to founder effects, stochastic demographic events and inbreeding depression. These factors raise the extinction probability of small populations, and thus effective management plans for endangered species have become essential. The black rhinoceros (Diceros bicornis) survived a historic global population crash and i...

The persistence of black (Diceros bicornis minor ) and white (Ceratotherium simum simum) rhinoceroses in the Kruger National Park (Kruger) is a key requirement for global rhinoceros conservation targets.Yet, poaching for rhinoceros horn poses a threat. In response, authorities are implementing an integrated response to curb the effect of poaching o...

Conservation management is of increasing importance in ecology as most ecosystems nowadays are essentially managed ones. Conservation managers work within a political-ecological system when they develop and attempt to implement a conservation plan that is designed to meet particular conservation goals. In this article, we develop a decision support...

The considerable threats of invasive rodents to island biodiversity are likely to be compounded by climate change. Forecasts for such interactions have been most pronounced for the Southern Ocean islands where ameliorating conditions are expected to decrease thermal and resource restrictions on rodents. Firm evidence for changing rodent populations...

South African National Parks (SANParks) manage landscapes rather than numbers of elephants (Loxodonta africana) to mitigate the effects that elephants may have on biodiversity, tourism and stakeholder conservation values associated with protected areas. This management philosophy imposes spatial variability of critical resources on elephants. Resto...

Information on large carnivore diet composition is important when conservationists seek to address stressors such as habitat encroachment, bush meat trade and retribution killing on the persistence of populations. Detailed diet sampling approaches can contribute to effective conservation management. We compare different approaches including GPS clu...

African lions (Panthera leo) are threatened across their natural range. However, the Kgalagadi Transfrontier Park (KTP) is a stronghold for the species.A population assessment in 2010 observed a skew in the sex structure with a greater proportion of males (56%) which raised concerns about the long-term sustainability of the greater KTP lion populat...

Interdiction patrolling (also known as hot spots policing) is a proactive police operation that depends on good planning. And the pursuit of fleeing suspects is a challenging operation that all police forces engage in on a regular basis. We give software tools that improve the effectiveness of both. We demonstrate the effectiveness of our tools by...

African rhinoceroses (rhinos) experienced a poaching onslaught since 2008 with the epicentre in South Africa where most of the world’s rhinos occur. South African national parks, under the management of South African National Parks (SANParks), are custodian to 49% of South Africa’s white and 31% of the country’s black rhinos. We collated informatio...

Aims Indicators of pending state-shifts carry value for policy makers. Predator–prey relations reflect key ecological processes that shape ecosystems. Variance in predator–prey relations may serve as a key indicator of future state-shifts. Methods Lion (Panthera leo) diet in the Kruger National Park was evaluated as such an indicator. Over the thr...

Background The range, population size and trend of large carnivores are important parameters to assess their status globally and to plan conservation strategies. One can use linear models to assess population size and trends of large carnivores from track-based surveys on suitable substrates. The conventional approach of a linear model with interce...

The onslaught on the World’s wildlife continues despite numerous initiatives aimed at curbing it. We build a model that integrates rhino horn trade with rhino population dynamics in order to evaluate the impact of various management policies on rhino sustainability. In our model, an agent-based sub-model of horn trade from the poaching event up thr...

Cross-validation statistics used to assess the economic-ecological model’s validity. (DOCX)

Definition and justification for the term SEAR trader. (DOCX)

Statistical estimators that could be used to estimate rhino horn demand, supply, and retail price. (DOCX)

Sensitivity analysis of the economic-ecological model. (DOCX)

African elephants (Loxodonta africana) are imperiled by poaching and habitat loss. Despite global attention to the plight of elephants, their population sizes and trends are uncertain or unknown over much of Africa. To conserve this iconic species, conservationists need timely, accurate data on elephant populations. Here, we report the results of t...

Spotted hyaenas (Crocuta crocuta) experience a range of influences that affect their demography and are generally regulated by density-dependent mechanisms. Although widely distributed across sub-Saharan Africa surprisingly few spotted hyaena populations have reliable estimates of population sizes, and almost nothing is known about the trends in hy...

Northern Botswana example of stratification and transect design as used on the GEC (A) Stratum design and sampling intensity (color) used on the northern Botswana GEC survey in 2014. (B) Transect design used on the northern Botswana GEC survey in 2014. Tracks shown are the actual tracks recorded on survey aircraft.

Estimated elephant populations in protected and unprotected areas by country on GEC surveys Error bars indicate ± 1 SE.

Relationship between carcass ratio on GEC surveys and estimated population trends from 2010-2014, by country Country codes: AGO–Angola, BEN–Benin, BWA–Botswana, BFA–Burkina Faso, CAM–Cameroon, TCD–Chad, DRC–DR Congo, KEN–Kenya, MWI–Malawi, MLI–Mali, MOZ–Mozambique, NER–Niger, TZA–Tanzania, UGA–Uganda, ZMB–Zambia, ZWE–Zimbabwe.

Elephant population estimates by ecosystem and stratum on GEC study areas

Explanation of simulations used to evaluate Monte Carlo methods discussed in the main text

Estimated exponential population growth rates (r) on GEC survey areas by country and start year, with 95% confidence limits Rows in bold indicate r significantly >0; rows in italics indicate r significantly <0.

Estimated elephant population totals by ecosystem on GEC surveys See Fig. S1 for ecosystem names.

Sampling effort and dates in GEC study areas Abbreviations: R: reserve, NP national park, NR: national reserve, CWA: community wildlife area.

GEC survey data Population estimates from GEC survey areas used to calculate country- and continent-wide statistics.

Historical data used to analyze trends in elephant populations File includes GEC and historical estimates used to estimate trends in elephant populations from 1995-2014.

Study ecosystems surveyed on the GEC in 2014–2015 Individual ecosystems are denoted by distinct colors. (A) overview map of the continent. (B), (C), & (D), study ecosystems by region, with names in italics.

Flow chart illustrating procedures used to estimate trends in elephant populations Hypothetical data (uppermost box) were created for this example, but numbers in boxes in subsequent steps are actual model output using the hypothetical data as input.

Estimated carcass ratios by protected status within countries on GEC surveys (A) ratios for all carcasses. (B) ratios for fresh carcasses. Only countries with elephant populations in both protected and unprotected areas are shown. Error bars indicate ±1 SE. Country codes: AGO–Angola, BWA–Botswana, TCD–Chad, KEN–Kenya, MOZ–Mozambique, TZA–Tanzania,...

Study areas used in analysis of historical trends in elephant popualtions, by country Unique colors signify different strata. Strata names are in italics.

Historical elephant population estimates used to estimate population trends Data points in 2014–2015 are from the GEC; earlier estimates come from published and unpublished reports and surveys. For Tsavo-Amboseli, the vertical line indicates an additional, non-GEC survey conducted in 2014.

Great Elephant Census survey standards

Elephants and fire can modify African savanna ecosystems. The authors evaluated the influence that elephants and fires had on five mountainous plant communities in Marakele National Park. These plant communities were surveyed from 1996 to 2010 with the first sampling in 1996 in the absence of elephants. Initially thirty-nine elephants, introduced i...

The better performance of large mammal populations in southern African protected areas is related to particular conservation values and historical and socio-economic circumstances. This chapter identifies a key set of desirable conservation, socio-economic, and political outcomes that are necessary to maintaining viable antelope populations in and...

Emerging infectious diseases of wildlife are of increasing concern to managers and conservation policy makers, but are often difficult to study and predict due to the complexity of host-disease systems and a paucity of empirical data. We demonstrate the use of an Approximate Bayesian Computation statistical framework to reconstruct the disease dyna...

Wildlife trafficking, a focus of organized transnational crime syndicates, is a threat to biodiversity. Such crime networks span beyond protected areas holding strongholds of species of interest such as African rhinos. Such networks extend over several countries and hence beyond the jurisdiction of any one law enforcement authority. We show how a f...

We develop a risk intelligence system for biodiversity enterprises. Such enterprises depend on a supply of endangered species for their revenue. Many of these enterprises, however, cannot purchase a supply of this resource and are largely unable to secure the resource against theft in the form of poaching. Because replacements are not available onc...

The onslaught on the World's rhinoceroses continues despite numerous initiatives aimed at curbing it. When losses due to poaching exceed birth rates, declining rhino populations result. We used previously published estimates and growth rates for black rhinos (2008) and white rhinos (2010) together with known poaching trends at the time to predict p...

Emerging infectious diseases of wildlife are of increasing concern to managers and conservation policy makers, but are often diffi cult to study and predict due to the complexity of host-disease systems and a paucity of empirical data. We demonstrate the use of an Approximate Bayesian Computation statistical framework to reconstruct the disease dyn...

A key concern for South African National Parks, within contractual park areas, is habitat degradation associated with large herbivore disturbances, especially when these include extralimital species.We used a mechanistic framework to bring contrasting views together for better interactions betweenWest Coast National Park management and stakeholders...

Understanding of the underlying processes that drive coexistence among apex predators is of great importance to landscape managers overseeing their persistence. Two pressing questions stand out. These questions relate to whether space use by subordinate carnivores is a function of resource distribution and shifts in resource availability or fine sc...