Browsing by Author "Naude, Vincent"

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    Heavy metal and organic compound bioaccumulation in bronze whaler sharks (Carcharhinus brachyurus) along the coastline of South Africa
    (2024) Adebowale, Adetola Q; O'riain, Mannus; Naude, Vincent
    Anthropogenic activities may release harmful contaminants into the environment which are subsequently ingested and gradually bioaccumulated up the food-web. As apex predators, sharks are prone to heavy metal and persistent organic pollution, being especially vulnerable to such exposure over long lifespans, making these species indicators of systemic pollution in marine ecosystems. As tons of shark meat is harvested annually for consumption, the risk of human exposure to these harmful bioaccumulated pollutants cannot be over-emphasized. In this study, we examined heavy metal and persistent organic pollutant concentrations in the muscle tissue of 41 bronze whaler sharks (Carcharhinus brachyurus) sampled along the southern and eastern regions of the South African coastline. The concentrations of 10 heavy metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, and Zn) and 8 congeners of polychlorinated biphenyls (PCB 28, 52, 101, 118, 138, 153, 180, 194) were analysed with inductively coupled plasma optical emission (ICP-OES) and gas chromatography coupled with low resolution mass spectrometry (GC-LRMS), respectively. Average concentrations of mercury (2.53 ±0.44 mg/kg), arsenic (16.60 ±1.38 mg/kg) and chromium (0.31 ±0.07 mg/kg) exceeded the World Health Organisation and other internationally recognised regulatory maximum limits for human consumption, while lead (0.14 ±0.09 mg/kg) and zinc (13.70 ±1.74 mg/kg) was close to the permissible limit. Aluminium, cadmium, copper, iron, manganese, and zinc were well below these regulatory limits, including those set by the Department of Health in South Africa and all PCB congener concentrations were below detectable limits. There were no significant differences in heavy metal concentration between sexes, except for chromium which was significantly higher in male sharks. We found that heavy metal concentrations varied significantly with shark size and sampling region. Mercury, chromium, and iron concentrations correlated positively and significantly (Hg: r = 0.78; Cr: r = 0.60; Fe: r = 0.47) with shark size (i.e., total length and body weight) while manganese had a strong negative correlation (r = -0.42). Cadmium, chromium, iron, and mercury concentrations were significantly higher in both adult (>230 cm) and sub-adults (130–230 cm) than in juvenile sharks (<130 cm) while manganese and aluminium concentrations were significantly higher in juvenile sharks. Mercury, iron, cadmium, and chromium concentrations were significantly higher in sharks sampled on the eastern coast while aluminium and manganese were higher in sharks from the southern coast of South Africa. Significantly positive and negative correlations were also found between heavy metals, suggesting underlying and systemic interactions between these pollutants. Our results underscore the ecological threat of heavy metal pollution along the South African coastline and the potential toxicity of consuming such shark meat from small-scale fisheries (i.e., high levels of mercury, arsenic and chromium toxicity have lethal effects). Potential sources of these heavy metal and organic pollutants include improper sewage treatment, dysfunctional waste-water treatment plants, and mining activities both inland and along South African coastline. Building on these study findings alongside existing literature and international policy, we suggest several recommendations to reduce such pollution and promote shark health and conservation in South Africa. Furthermore, detailed guidelines on safe shark meat consumption and more stringent environmental policies around waste-water management should be considered by the Departments of Health and Forestry, Fisheries, and the Environment in South Africa.
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    The threat of terrestrial predators to mainland penguin colonies: searching for sustainable solutions
    (2023) Rhoda, Linden; O'Riain, Justin; Naude, Vincent
    Anthropogenic activities including overexploitation of natural resources and the transformation of natural habitat have disturbed ecological systems and are increasingly challenging the natural persistence, movement, and interactions of wildlife populations. On the Cape Peninsula in South Africa, all large predators were extirpated to reduce threats to lives and livelihoods with the medium-sized caracal (Caracal caracal) emerging as the de facto apex predator. Overexploitation of Africa penguins (Spheniscus demersus), their prey and their island breeding sites in the south-western Cape resulted in a rapid decline in the African penguin population and a shift in their distribution. This shift coincided with the establishment of at least four mainland colonies, one of which is on the Cape Peninsula. In this manner a Least Concern, abundant predator encountered an Endangered bird species poorly adapted to terrestrial predators, setting the scene for a conservation conflict in the Anthropocene. My goal in attempting to mitigate this conflict was to first collate all available data on mainland penguin colony demographics and to understand the relative threat posed by terrestrial predators such as caracal on their mortality. Secondly, I reviewed historical and current management interventions by conservation authorities to protect mainland colonies from terrestrial predators and assessed both their success in protecting penguins and their impacts on the predators. Having identified discrepancies amongst stakeholders in how best to manage the interface between penguins and predators I reviewed the potential non-lethal and lethal methods and used a standardised evaluation scoring system to identify those strategies with the most support. I then developed a management plan that integrates these strategies and provides the most sustainable solution for reducing supernumerary predation events while also offering conservation benefits to caracal. I made use of a qualitative triangulation approach for the evaluation of management techniques as this explores anecdotal data from case-studies alongside the individual experiences of environmental managers and experts in the field. Annual counts at mainland penguin colonies revealed that only two of the four colonies had persisted, and both had exhibited strong early growth and were now recognised as important breeding sites with high conservation status. Surprisingly both surviving mainland colonies were established in peri-urban areas with high levels of anthropogenic disturbance including vehicular collisions, and disturbance by domestic animals and people. Leopard (Panthera pardus pardus) and caracal were both identified as posing a significant threat to the viability of the Stony Point and Simon's Town penguin populations respectively. Both predators had engaged in supernumerary predation events, which have cumulatively resulted in the recorded deaths of at least 346 penguins over the last decade. In response to predations local statutory authorities have attempted numerous intervention strategies at both colonies. Remote camera traps proved effective at early detection and identifying species responsible, while physical barriers were effective at reducing access to colonies. Capture and collaring of caracal on the Peninsula with follow-up monitoring of movement adjacent to the colony proved ineffective as the caracal readily evaded staff deployed to deter them. Relocation of caracal within the Peninsula has had limited success as only one individual established a stable territory far from the colony, while the remaining cats either returned to the colony or died in vehicular collisions. The average time between supernumerary predation events following relocations or the euthanasia of caracal was approximately six months. A total of 17 primary mitigation management interventions were evaluated by key stakeholders with three having high levels of support visà-vis: cameras for early detection of potential predators, physical barriers to deter entrance to the colony or funnel predators into capture cages for translocation to other protected areas within the City of Cape Town (CoCT). Together with local conservation authorities and managers these three interventions were then integrated into a management plan with standard operating procedures and a decision flow chart so as to 1) greatly reduce predation on penguins by terrestrial predators, 2) prioritise non-lethal interventions including the development of a translocation plan to CoCT nature reserves, 3) ensure the plan aligns with current local and international (IUCN) policy, 4) be cost effective and practically achievable with the resources available, and 5) have broad public, stakeholder, and statutory acceptability. Together these interventions provide a solution to a classic conservation conflict in the Anthropocene and can serve as a suitable template for the management of Least Concern predators impacted by urban development both in South Africa and elsewhere in the world.
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    Under the skin of a culture: perceptions of fake leopard skin alternatives in the Shembe Baptist Church
    (2024) Mabaso, Xolani X; O'riain, Mannus; Nattrass, Nicoli; Naude, Vincent
    Since prehistoric times, big cats such as leopards have had symbolic importance in human culture. They are prized as symbols of power, nobility, ferocity and very often, masculinity. Religious groups have also been known to wear animal skin as part of their ceremonial regalia, typically for aesthetic, superstitious and spiritual reasons. However, throughout much of their historical distribution, leopards have been actively hunted, poached or killed in retaliation for livestock losses so extensively that many of their populations are now under direct threat. Despite attempts to control illegal harvesting and trade through international conservation organizations such as CITES the use of and trade in leopard products remains commonplace throughout their range. In Southern Africa one of the most widespread and obvious users of leopard skins are members of the Shembe Nazareth Baptist Church. The Shembe church, which has approximately 6 million followers, was founded by Prophet Isaiah Shembe on 1910 in Durban, South Africa. This modern take on Zionist beliefs integrates aspects of Christianity and traditional Zulu beliefs. Followers wear white, full length garments when praying and a diverse array of animal skins when engaging in traditional dance. The most popular and prestigious animal skin is that of a leopard. Given concerns around the increasing demand for leopard skins, Panthera (cat conservation NGO) initiated the Furs for Life project in 2013, introducing synthetic leopard skin alternatives to real skins. These ‘faux' skins were donated to the Shembe church for dissemination among their followers, with the hope that this would ultimately reduce demand for real skins. While approximately 24,000 faux furs have been distributed within the Shembe church to date, little is known about how well these have been received or how effective this conservation intervention has been. In this brief, exploratory study 100 randomly selected recipients of faux furs were surveyed to address concerns pertaining to: faux fur use, demand for real skins, consumer satisfaction, knowledge of conservation and policy perceptions, through a descriptive statistics and basic generalised linear model framework. We found that after a period of three years, at least 90% of the respondents still have their fake furs, have been using them approximately six times a year and were positive about the product they received from Panthera. More than 60% of respondents are aware of leopard population trends, and 66% of respondents believed that the government should intervene in leopard conservation. Faux leopard furs have been very successful, reporting a higher than 50% usage in Shembe gatherings, with most respondents indicating how aesthetic and durable faux furs are as well as how similar they are to real leopard fur. As this was a pilot study with only 100 respondents so statistical power was limited given the number of variables, we suggest a similar study done on a larger scale to understand the efficacy of the intervention.