Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 81.82K | Year: 2011
The race for survival is common to all living organisms: when it comes to predator-prey interactions, this involves predators developing more effective means to catch prey whilst their prey counteracts with new evasion tactics. Energy is a primary limiting resource in most natural systems. To understand how energy budgets compel certain species to inhabit specific environments, it is necessary to identify a species that displays extreme energy requirements. Within mammals, large predators often experience high energy costs while hunting and it is suggested that this may restrict their ecological niches, obliging them to inhabit only areas with abundant food sources and minimal competition. However, no study has yet attempted to measure energy expenditure in a large carnivore while simultaneously monitoring interactions between competitors and prey. With the greatest power output for their size of any mammal and the greatest speed reached on land, cheetahs (Acinonyx jubatus) are positioned at an apex in the topography of evolutionary adaptation. Does such an evolutionary peak come with a cost? Research suggests cheetahs are severely restricted in their abilities to acquire and utilise energy. In the current study, we will measure energy expenditure in free-ranging cheetahs to determine which behaviours or circumstances cause particular energetic constraints. Cheetahs are built for speed, accelerating from 0 to 30 kph in three strides and reaching a maximum speed of about 110 kph in 4 seconds. At full speed, the cheetah is running at about three strides per second and the respiratory rate climbs from 60 to 150 breaths per minute. Cheetahs can only maintain this for a few hundred metres before exhaustion. Such a high-speed foraging strategy imposes severe limits on all other aspects of their lives, leaving them vulnerable to starvation, or to reproductive failure due to lack of energy. This is because their predation tactics are energetically costly, and, being built for speed rather than strength, they are easily driven off their prey by more robust rival species. Consequently, cheetahs are suggested to be at an energetic edge, with the viability both of individual animals and populations depending on how close individuals approach the evolutionary limits of energy supply and demand. An understanding of their energetic tactics will therefore help provide insights as to how energetic constraints can shape the evolution of these super-predators. Energy use will be measured using the doubly labelled water technique  whilst field observations will be made of activities and of incidents where rival species steal prey or interact with cheetahs in other ways that may affect their energy balances. In addition, multi-channel data loggers -daily diaries - will be attached to the cheetahs using collars for up to 80 days at a time. These devices provide data on detailed movement in three dimensions  at a very fine resolution (32 Hz). Interpretation of the resulting electronic traces recorded will reveal the time spent on various activities such as resting, feeding, walking and running. The data will also be used to calculate a proxy of energy expenditure, known as overall dynamic body acceleration. This will complement the energetics data and provide a fine-scale record of continuous activity. Thus, individual activities and their associated energy costs will be elucidated to paint a complete picture of the animals energy budgets. The study will provide valuable information as to how carnivores in general manage their energy budgets. It will also demonstrate how the measurement of physiological characteristics can help determine the long-term viability of rare and threatened species. Thus we shall be providing insights into how energetic constraints can shape species viability.  Speakman, J.R. Doubly Labelled Water. 1997. Chapman and Hall.  Wilson, R.P. et al. 2008 Endang. Species. Res. 3:1-15
Russell I.A.,South African National Parks
African Zoology | Year: 2011
Thirteen of South Africa's national parks contain aquatic systems which support 63 indigenous and 11 alien freshwater fishes. Indigenous fishes include 43 species of the Zambezian faunal group (70% of the national total), eight Karroid (47%), five Cape (31%) and seven species of Marine origin (79%). Six represented Zambezian species, two Marine origin, and all of the Cape and Karroid species are endemic to South Africa. Only three threatened species naturally occur within national parks (Serranochromis meridianus, Barbus andrewi, Pseudobarbus afer) all of which are classified as Endangered. Two extralimital IUCN threatened species (Chetia brevis and Oreochromis macrochir) have been introduced. At least three of the five lineages of Galaxias zebratus and two of the four lineages of Pseudobarbus afer occur within national parks in the Cape region. Many fish populations within national parks remain threatened, particularly by hydraulic alterations, impoundment, and predation by alien fishes. There are few aquatic systems within national parks where one or more of these threats are not prominent, and these collectively support only half of the freshwater fish species occurring in all national parks. Proposed management actions include determination and implementation of Environmental Flow Reserves in stressed systems, management of existing alien fish populations and prevention of new establishments, and regular assessments of fish communities.
Scholes R.J.,South African Council for Scientific and Industrial Research |
Kruger J.M.,South African National Parks
Koedoe | Year: 2011
Ecosystems are characterised by complexity: high connectivity, the presence of positive and negative feedback loops, non-linear, abrupt and sometimes irreversible changes, delays between cause and effects, and uncertainties in observations, understanding and prediction. 'Adaptive management' is the preferred approach for the rational management of such systems. Where the management objective is to allow natural feedbacks and adaptive processes to operate as much as possible - as it is in many areas set aside for biodiversity conservation - a key issue is defining the thresholds that will trigger management intervention. This paper outlines and illustrates a logical process for doing so, taking into account the characteristics of complex, continuously changing ecosystems and the reality of information that is partial and understanding that is always provisional. After identifying a key ecological process that is believed to have an element of irreversibility beyond a certain point, the process has several steps, (1) define an indicator of the system state, (2) set a limit of acceptable change and add a safety margin, (3) project the indicator forward using a model, including uncertainty, (4) note the time when the indicator might transgress the safety-buffered limit and (5) subtract ecosystem and management response times. If the resultant time is at hand, an action is indicated - if not, the action is to continue to monitor the situation and refine the observations and models. Conservation implications: Ecosystems are characterized by abrupt and sometimes irreversible changes. The challenge that face conservationists and managers are to identify which of these changes are likely to be irreversible and at what levels this will occur. This paper describes a logical process that enable mangers to determine which ecological processes have levels of irreversibility and monitor their status at all times. Once these processes are nearing the levels that are undesirable management actions can be invoked to prevent this from happening. © 2011.
Russell I.A.,South African National Parks
African Journal of Aquatic Science | Year: 2015
Variability of salinity, temperature, pH, dissolved oxygen and turbidity in the temporarily open/closed Swartvlei estuarine system, measured from 1991 to 2013, was investigated at various temporal (seasonal, estuarine open/closed phase, long-term) and spatial (inter- and intra-waterbody) scales. Longitudinal pH and salinity gradients, and seasonal variability of temperature and dissolved oxygen, were typical of many southern African estuaries. Differences to comparable systems occurred with respect to temperature range, and within-system variability of salinity, pH and dissolved oxygen. The influence of differing marine and freshwater inflows, and of submerged macrophyte composition and biomass, on such variability are discussed. No significant long-term changes occurred in salinity or pH up until 2006. Significant freshwater flooding in mid-2006 and late 2007, and following increases in open-mouth conditions, resulted in significant decreases in pH in both Swartvlei Estuary and Swartvlei Lake, and increases in salinity throughout the system. Long-term declines in turbidity occurred in Swartvlei Estuary throughout the study period. No long-term changes in water temperature were recorded. Long-term data indicate that the Swartvlei system is not undergoing a rapid deterioration in water quality, but rather exhibiting both short- and long-term fluxes characteristic of estuarine systems. © 2015, Copyright © NISC (Pty) Ltd.
Smit I.P.J.,South African National Parks |
Smit I.P.J.,University of Cambridge
Ecography | Year: 2011
In order to effectively manage and conserve indigenous herbivores, a good understanding is needed of how resources drive their distribution patterns. This study employed a unique dataset to test a range of ecological theories and hypotheses on free-ranging grazers. Using aerial census data collected over 14 yr across the 2 million ha Kruger National Park (South Africa), this study employs spatial autologistic regression models to explore the spatial relationships that exist between the distribution of eight indigenous grazer species and a set of resource variables. It was found that ecological theories relating to feeding guild, water-dependence, allometric scaling, gut-morphology and vulnerability to predation could explain most of the grazer distribution patterns observed in relation to surface-water, forage quality, forage quantity and habitat openness. All the grazers studied were water-dependent and occurred close to a permanent source of water in the dry season. This was ascribed to the lack of moisture in the diet of grazers during the dry season. Most ruminants' distribution patterns were significantly associated with areas of high forage quality whereas hind-gut fermentors were neutral towards forage quality. Average forage quantity was not a significant predictor of long-term, landscape-scale distribution patterns for any of the grazer species studied. Most small- and medium-bodied grazers preferred open habitats above closed habitats, probably due to higher visibility and a lower predation risk. Large-bodied grazers did not bias their distribution patterns towards open habitats. The way in which grazers distribute themselves with respect to different resources can potentially inform management actions on appropriate scales. © 2011 The Authors.
van Wilgen B.W.,Center for Invasion Biology |
van Wilgen B.W.,South African Council for Scientific and Industrial Research |
Forsyth G.G.,South African Council for Scientific and Industrial Research |
Prins P.,South African National Parks
Ecology and Society | Year: 2012
The Table Mountain National Park is a 265-km 2 conservation area embedded within a city of 3.5 million people. The highly diverse and unique vegetation of the park is both fire prone and fire adapted, and the use of fire forms an integral part of the ecological management of the park. Because fires are both necessary and dangerous, fire management is characterized by uncertainty and conflict. The response of vegetation to fire is reasonably well understood, but the use of fire for conservation purposes remains controversial because of key gaps in understanding. These gaps include whether or not the vegetation is resilient to increases in fire frequency, how to deal with fire-sensitive forests embedded in fire-prone shrublands, and how to integrate fire and invasive alien plant control. National legislation emphasizes the need to protect communities from dangerous wildfires, and this compels fire managers to adopt a cautious approach to the application of fire. Ecological outcomes are optimized under a fire regime of relatively high-intensity, dry-season fires. Obtaining permission to burn under such conditions is not possible, and so the practice of prescribed burning is constrained, and this results in a fire regime dominated by wildfires. Ecological uncertainties, and the divergent requirements for maintaining healthy ecosystems on the one hand, and ensuring human safety on the other, result in a complex fire management environment. These complexities could be, and in some cases are being, alleviated by raising awareness, increasing fire management capacity, improving ecological monitoring of the effects of fire, and prioritizing areas for integrated fire and invasive alien plant management. © 2012 by the author(s). Published here under license by the Resilience Alliance.
du Toit D.R.,Water and Rural Development |
Biggs H.,South African National Parks |
Pollard S.,Water and Rural Development
Ecology and Society | Year: 2011
Equitable redistribution of resources is an emergent phenomenon in democratizing countries, and attempts are often characterized by decentralized decision making within a framework of multistakeholder negotiations. South Africa offers a unique opportunity to explore the manifestations of these relationships, particularly through Integrated Water Resources Management and its National Water Act of 1998. The Integrated Water Resources Management framework provides for collaborative strategic planning, shared visioning, consideration to water resource protection, attention to the regulation of use, operational planning, and implementation of management plans. Water users, with different stakes and views of how the resource should be managed, are expected to arrive at a single strategic plan for a specific hydrological region. Clearly this complex planning situation creates a need for tools that assist in producing a measure of convergence in thinking and enough of a shared rationale to allow stakeholder participation to produce an integrated management outcome. Several such tools are available in the overall catchment management strategy, but these would benefit from clearer understanding of the positions from which different stakeholders are operating and a way of knowing whether these positions are aligning. In this paper challenges posed by differences in meaning and understanding amongst stakeholders are examined against the need to engage stakeholders in water resources management. We deliberate on the prospects of employing mental model methodologies within the context of the strategic management framework for water management described. © 2011 by the author(s).
Hanekom N.,South African National Parks
African Zoology | Year: 2013
Mass mortalities of the ascidian Pyura stolonifera occurred along the Tsitsikamma coast in May 1991 and again in February 2012, following infection of large proportions of the population with a white microbial growth. P. stolonifera appeared to be the only species affected, with the outer tunic the main site of infection. No signs of pollution or algal blooms were observed, but large variations in climatic conditions were associated with both events. The 1991 mortalities occurred during a warm spell in autumn, when there was a rapid increase in the daily air temperatures. Similarly, the February 2012 event occurred after abnormally high air temperatures of January 2012 declined sharply due to a cold-water upwelling event in early February. These findings are compared with those of other marine disease and mortality studies.
Russell I.A.,South African National Parks
African Journal of Aquatic Science | Year: 2013
Long-term (20+ years) water quality datasets for estuaries are rare, especially for smaller systems. Monitoring of salinity, temperature, pH, dissolved oxygen and turbidity has been undertaken since 1991 in the intensively utilised, modified, and managed temporarily open/closed Touw Estuary and its associated three interconnected estuarine lakes, Eilandvlei, Langvlei and Rondevlei, of the Wilderness Lakes System, South Africa, a national park and Ramsar site. Spatial variability of salinity, pH and turbidity was pronounced in the Touw Estuary but largely absent in the lakes. Significant differences in median salinity, pH, dissolved oxygen and turbidity occurred between lakes, with reverse salinity and pH gradients frequently occurring. Seasonal variability in temperature and dissolved oxygen occurred in all waterbodies. Significant long-term declines in salinity have occurred in the more inland lakes, with decreases in turbidity and pH also occurring in some waterbodies. Water chemistry of the Wilderness Lakes is changing from that of an estuarine to a lacustrine system. Both biological and physical features were driving water quality changes, including reductions in river inflow, reduced marine connectivity, constriction of flow between waterbodies, and declines in submerged plant biomass. Management actions are proposed relating specifically to addressing the apparent causes for water quality changes. © 2013 Copyright NISC (Pty) Ltd.
News Article | September 20, 2016
KRUGER NATIONAL PARK, South Africa (Reuters) - South Africa's Kruger National Park is littered in places with the trunks of trees uprooted and stripped of bark by a surging population of elephants, a frequent sight in the reserve. Africa's elephants are still threatened by poachers seeking to kill them for their ivory tusks but in several southern states populations have rebounded, helped by conservation policies and the remote locations where many of the herds live. The numbers are now so big that some countries say the world's largest land mammal is causing too much damage to crops, threatening the livelihoods of poor subsistence farmers and the populations of other species including birds, bats and woody plants in forests uprooted by elephants. Zimbabwe and Namibia have asked for a global ban on ivory trade to be lifted so that they can use the proceeds of national stockpiles of tusks to fund conservation and support communities living near elephants. "Elephants are regarded as a liability and economic cost to rural communities, who suffer crop losses, other damages and lose human lives," Namibia's proposal says. Its population has increased to 20,000 from 7,500 the past two decades. The request to sell stockpiles, collected through seizures of contraband, natural mortality in the wild and the shooting of problem animals, will be considered at a meeting of the U.N.'s Conference on International Trade in Endangered Species (CITES) in Johannesburg from September 24 to October 5. The ban on trade in ivory products was imposed in 1989 in response to a wave of poaching, though domestic trade has remained legal in a number of countries including China. The United States in July imposed a near-total ban on domestic ivory sales within its borders. Opponents are concerned that if CITES allows ivory to be traded, even from stockpiles and as a one-off, it would send a signal that it is socially acceptable, which could spur demand and further poaching. Ivory is particularly coveted in Asia where it is used for carving and jewelry. Botswana, Namibia and Zimbabwe were given permission to sell stockpiles to Japan in 1999 and were joined by South Africa in 2008 in a sale to China and Japan. A June 2016 study by the U.S. National Bureau of Economic Research found that the 2008 sale likely led to an increase in elephant poaching. It noted an estimated 71 percent increase in ivory smuggling out of Africa "while corresponding patterns are absent from natural mortality and alternative explanatory variables. These data suggest the widely documented recent increase in elephant poaching likely originated with the legal sale." Poaching has skyrocketed in the past decade in much of the continent to feed the illicit market, lending a new sense of urgency to campaigns to completely close the trade for good. For their request to pass, Zimbabwe and Namibia will need the support of two-thirds of the 183 member states of CITES. South Africa Environment Minister Edna Molewa told Reuters that her country and others in southern Africa would support the Namibian and Zimbabwean proposals because the ivory sales were needed to pay for the ecological and social costs of large elephant populations. "If you look at the communities that are bearing the brunt of living with these animals, their ecological systems are degraded and they lose food security and grazing lands," she said. She said "we are quite optimistic" the proposals would pass but expected tough negotiations. There is expected to be significant opposition from most western countries, some NGOs and African countries including Kenya, which along with others has made a separate proposal to CITES to keep the trade ban firmly in place. Sport hunting of elephants is permitted in some countries such as South Africa and Zimbabwe and hunters are allowed to keep the tusks as trophies. But in Kenya, where elephants cannot be owned and where any hunting is forbidden, the animals are seen as a bigger draw for tourists wanting to see them in the wild. Kenya and Gabon, which has large areas of national park and is fighting a growing battle with poachers, have burnt ivory stockpiles. And while elephant populations are stabilizing in southern Africa where conservation policies are stronger, in east and central Africa, poaching is rife and the numbers are down. A census by Elephants Without Borders, a conservation group, found numbers of Savanna elephants - which favor more open habitat - fell 30 percent between 2007 and 2014 to 350,000. Africa's other species, the forest elephant, will need a century to recover from poaching because of its slow birth rate, and numbers around 70,000. Zimbabwe says its elephant population has stabilized at 80,000. Its proposal says elephant populations exceeding 0.5 per km have a detrimental impact on woodlands and other species. However, scientists say the damage done by elephants is being exaggerated and that they are crucial for healthy ecosystems because their dung disperses seeds and fertilisers and they create habitats for smaller creatures through foraging. "Elephants are a key driver in maintaining biodiversity," said Sam Ferreira, a South African National Parks ecologist. "No species in the Kruger has ever gone extinct because of elephants." Since culling was halted at Kruger in 1994, the elephant population has swollen from around 8,000 to 17,000 - and other animals have not suffered, he said. In Chobe National Park in northern Botswana, where the number of elephants has risen to 130,000 from 30 in 1930, scientists say antelope species such as impala have benefited from the removal of trees by elephants as they favor shorter vegetation. This in turn has boosted the populations of predators such as lions. There is agreement, however, that elephants in Namibia and Zimbabwe are making life hard for the humans living nearby. Zimbabwe's Campfire Association say elephants eat around 18 percent of the crops in the poor communities where the NGO works. It says people have been killed by then, often when subsistence farmers come across the animals in their fields. Cash-strapped Zimbabwe, which has a 70 tonne ivory stockpile worth $35 million, says ivory trade is the only way to pay for protecting its elephants and to give rural communities an economic incentive for living near the animals. Nevertheless, conservationists say Zimbabwe and Namibia should not be given special treatment. "We do recognize that Zimbabwe and Namibia's elephants populations are in better shape than those elsewhere in Africa," said Susan Lieberman, vice president for International Policy at the Wildlife Conservation Society. "But it's rather short-sighted and a bit selfish for them to request to sell their ivory, knowing full well that it will further stimulate poaching and trafficking from other populations. The global community needs to see this as an Africa-wide issue."