Time filter

Source Type

Pretoria, South Africa

Holness S.D.,South African National Parks | Holness S.D.,Nelson Mandela Metropolitan University
Koedoe | Year: 2011

This article argues that systematic conservation planning (SCP) is an intrinsic part of the adaptive management approach within SANParks and should not be seen as a separate or different initiative. SCP operates within a complex environment that requires a deliberately adaptive approach. The similarities in philosophy, structure and functional elements of the planning process and approach between adaptive management and SCP, as applied within SANParks, are highlighted. The article distils requirements for ensuring that SCP remains strategically adaptive in its approach. © 2011.

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 [1] 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 [2] 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. [1] Speakman, J.R. Doubly Labelled Water. 1997. Chapman and Hall. [2] Wilson, R.P. et al. 2008 Endang. Species. Res. 3:1-15

Kraaij T.,Scientific Services | Novellie P.A.,South African National Parks
African Journal of Range and Forage Science | Year: 2010

The Bontebok National Park has long been faced with the dilemma of reconciling the need for short-interval fires, which promote grazing for bontebok, with that for longer-interval fires to maintain plant diversity. We explored habitat selection by various large herbivores in relation to veld age (time since fire), different management regimes, and vegetation type. Taller grass grazers (Cape mountain zebra and red hartebeest) were introduced in the 1980s to prolong the usefulness of older veld to bontebok through a grazing succession. We found that all herbivores favoured young veld and largely avoided veld >5 years old. Zebra and hartebeest competed with bontebok in utilising young veld rather than grazing facilitation occurring. In 2004, the fire rotation was prolonged to favour plant diversity, resulting in reduced availability of young veld. In compensation, the bontebok stocking rate was reduced. Bontebok densities subsequently declined proportionally across veld ages, thereby averting high animal densities on the smaller area of young veld. Fire significantly influenced bontebok habitat use equally during the old and new burning regimes. Herbivores did not distinguish between the two predominant vegetation types at Bontebok National Park. However, previously disturbed areas with Cynodon dactylon lawns were favoured by most herbivores despite not being burnt. © NISC (Pty) Ltd.

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.

Discover hidden collaborations