Reflecting on research produced after more than 60 years of exclosures in the Kruger National Park

All data, in this case works of literature reviewed have been summarised in Online Appendix 2.Herbivores are a main driver of ecosystem patterns and processes in semi-arid savannas, with their effects clearly observed when they are excluded from landscapes. Starting in the 1960s, various herbivore exclosures have been erected in the Kruger National Park (KNP), for research and management purposes. These exclosures vary from very small (1 m2) to relatively large (almost 900 ha), from short-term (single growing season) to long-term (e.g. some of the exclosures were erected more than 60 years ago), and are located on different geologies and across a rainfall gradient. We provide a summary of the history and specifications of various exclosures. This is followed by a systematic overview of mostly peer-reviewed literature resulting from using KNP exclosures as research sites. These 75 articles cover research on soils, vegetation dynamics, herbivore exclusion on other faunal groups and disease. We provide general patterns and mechanisms in a synthesis section, and end with recommendations to increase research outputs and productivity for future exclosure experiments. CONSERVATION IMPLICATIONS : Herbivore exclosures in the KNP have become global research platforms, that have helped in the training of ecologists, veterinarians and field biologists, and have provided valuable insights into savanna dynamics that would otherwise have been hard to gain. In an age of dwindling conservation funding, we make the case for the value added by exclosures and make recommendations for their continued use as learning tools in complex African savannas.South African Environment Observation Network (SAEON).http://www.koedoe.co.zaam2023Paraclinical Science

Elephant population growth in Kruger National Park, South Africa, under a landscape management approach

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. Restoration of such ecological processes through less intensive management predicts a reduction in population growth rates from the eras of intensive management. We collated aerial survey data since 1995 and conducted an aerial total count using a helicopter observation platform during 2015. A minimum of 17 086 elephants were resident in the Kruger National Park (KNP) in 2015, growing at 4.2% per annum over the last generation of elephants (i.e. 12 years), compared to 6.5% annual population growth noted during the intensive management era ending in 1994. This may come from responses of elephants to density and environmental factors manifested through reduced birth rates and increased mortality rates. Authorities should continue to evaluate the demographic responses of elephants to landscape scale interventions directed at restoring the limitation of spatial variance in resource distribution on elephant spatiotemporal dynamics and the consequences that may have for other conservation values. Conservation implications: Conservation managers should continue with surveying elephants in a way that allows the extraction of key variables. Such variables should focus on measures that reflect on how theory predicts elephants should respond to management interventions

Species-specific drought impacts on black and white rhinoceroses.

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 uncertainties on the management and persistence of these species. The drought experienced in Kruger over the 2015/2016 rainy season may have affected rhino population growth and thus added an additional population pressure to the poaching pressure already occurring. Under drought conditions, reduced grass biomass predicts increased natural deaths and a subsequent decrease in birth rate for the grazing white rhino. Such variance in natural death and birth rates for the browsing black rhino are not expected under these conditions. We evaluated these predictions using rhino population survey data from 2013 to 2017. Comparisons of natural deaths and birth rates between pre- (2013/2014 and 2014/15), during- (2015/2016) and post-drought (2016/2017) periods in Kruger showed increased natural mortality and decreased births for white rhino, but no significant changes for black rhino, supporting our predictions. As a result, despite reduced poaching rates, the total mortality rate of white rhino remains significantly higher than the birth rate. Decreased poaching, decreased natural deaths and no apparent drought effects in black rhino resulted in a lower total mortality rate than the estimated birth rate in 2017. Active biological management and traditional anti-poaching initiatives together therefore represent the most likely way to buffer the impacts of decreased population growth through climate change and wildlife crime on the persistence of rhinos

Disruption of Rhino Demography by Poachers May Lead to Population Declines in Kruger National Park, South Africa.

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 population sizes and poaching rates in Kruger National Park, South Africa for 2013. Kruger is a stronghold for the south-eastern black rhino and southern white rhino. Counting rhinos on 878 blocks 3x3 km in size using helicopters, estimating availability bias and collating observer and detectability biases allowed estimates using the Jolly's estimator. The exponential escalation in number of rhinos poached per day appears to have slowed. The black rhino estimate of 414 individuals (95% confidence interval: 343-487) was lower than the predicted 835 individuals (95% CI: 754-956). The white rhino estimate of 8,968 individuals (95% CI: 8,394-9,564) overlapped with the predicted 9,417 individuals (95% CI: 7,698-11,183). Density- and rainfall-dependent responses in birth- and death rates of white rhinos provide opportunities to offset anticipated poaching effects through removals of rhinos from high density areas to increase birth and survival rates. Biological management of rhinos, however, need complimentary management of the poaching threat as present poaching trends predict detectable declines in white rhino abundances by 2018. Strategic responses such as anti-poaching that protect supply from illegal harvesting, reducing demand, and increasing supply commonly require crime network disruption as a first step complimented by providing options for alternative economies in areas abutting protected areas

The status of rhinoceroses in South African National Parks

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 information on rhino population sizes in seven national parks from 2011 to 2015. We include and report on rhino surveys in Kruger National Park during 2014 and 2015. Southwestern black rhinos increased over the study period, which allows SANParks to achieve its contribution to South Africa’s 2020 target of 260 individuals. South-central black rhinos declined over the study period because of poaching in the Kruger National Park, making it difficult for SANParks to realise a 9% increase per annum for its expected contribution to the South African target of 2800 individuals. For southern white rhinos, SANParks requires 5% annual growth for its contribution to the South African target of 20 400 individuals. To continue to evaluate the achievement of these targets, SANParks needs annual population estimates relying on total counts, mark-recapture techniques and block-based sample counts to track trends in rhino populations. SANParks’ primary challenge in achieving its contribution to South Africa’s rhino conservation targets is associated with curbing poaching in Kruger National Park. Conservation implications: The status and trends of rhino species in SANParks highlight key challenges associated with achieving the national targets of South Africa. Conservation managers will need to improve the protection of southern white rhino, while the Department of Environmental Affairs need to be made aware of the challenges specifically associated with not achieving targets for south-central black rhino. Outcomes for south-western black rhino have already realised and the good conservation efforts should continue

Predicted white rhino population estimates for 2018 under four different scenarios for poaching trends.

<p>LCL–Lower 95% Confidence Limit. UCL–Upper 95% Confidence Limit.</p><p>Predicted white rhino population estimates for 2018 under four different scenarios for poaching trends.</p

Population trends for rhinos in Kruger National Park.

<p>Black (A) and white (B) rhino estimates noted in Kruger National Park. We extracted previous estimates for black rhino [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127783#pone.0127783.ref005" target="_blank">5</a>] and white rhino [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127783#pone.0127783.ref009" target="_blank">9</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127783#pone.0127783.ref015" target="_blank">15</a>]. The line for white rhino comes from a published model [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127783#pone.0127783.ref009" target="_blank">9</a>].</p

Estimated vital rates for white rhinos noted in Kruger National Park.

<p>We present data for males (A) and females (B) since 2009. We also include management removal and poaching rates.</p

Estimated annual population growth rates as a function of population size.

<p>We illustrate how poaching and management removals may influence these relationships. Solid lines are significant relationships.</p