A day in the sun at a rotting carcass surrounded by lions may not be everyone’s idea of a successful day at the office, but for Dr Andrea Webster, faeces from different species provides valuable clues about how pollutants can affect wildlife populations in protected areas. Dr Webster is a postdoctoral fellow at the University of Pretoria’s Mammal Research Institute and recent recipient of a PD scholarship from the Oppenheimer Chair for Emerging Scientists in Non-invasive Wildlife Research Programme.
“Our assumption that protected areas are pristine environments needs to be re-evaluated if we are going to protect the biodiversity they support.” Although all chemicals can be hazardous, a specific group of pollutants known as endocrine disrupting chemicals or EDCs that includes metals, pesticides, plastics and other industrial products, can modify endocrine system function across generations. Consequences of endocrine disruption vary, but include hormonal imbalance, reduced immune response and compromised reproductive success. To complicate matters, underlying geological profiles, air quality and human activities inside and outside of protected area boundaries contribute to unique pollutant signatures in different wildlife areas.
Environmental pollutant levels in protected areas are typically monitored through the assessment of air, water and environmental quality. Unless mass die-off of wildlife occurs, such as the recent deaths of 300+ elephants in Botswana during 2020 from an unexplained cause, toxicological assessments seldom include real-time monitoring of pollution in free-ranging wildlife. Like all substances, toxins are metabolised and can be stored or accumulate in the body. Some compounds are metabolised without change to their chemical characteristics, while others undergo chemical alteration to form metabolites, which are often more toxic to an organism than the original compound.
Sampling from a mass die-off can be tricky for a number of reasons. Specific organs or tissues must be collected and tested for the right toxins. Additionally, animals must be discovered soon after death because environmental conditions degrade the carcass and insect and scavenger activity can compromise organ viability for testing. This is not always possible given the limited resources and the vast areas some African conservation areas cover. Establishing the links between cause and effect is often difficult to establish. Even when this can be done, its generally too late for affected animals to be saved; loss of wildlife and biodiversity can be substantial. This was readily demonstrated in the 2008 contamination of the Olifants River gorge, where more than 160 Nile crocodiles died from pansteatitis, and countless species of fish, birds and amphibians were lost.
Faeces from wild animals is readily available in the environment and can be used to non-invasively assess ecosystem integrity and levels of certain pollutants in different species. In contrast to information obtained from tissue sampling at mass die offs, faeces can be collected from a wide range of free-ranging species occupying a specific habitat with its unique toxin profile. Different species may be more susceptible to contamination than others, because of what they eat or how they behave. Predators at the top of the food chain for example, are often most affected because pollutants accumulate in the tissues of their prey.
Faecal assessments can help to understand these complex ecological interactions and flow of toxins through the food chain. When faecal sampling is conducted over a number of years and over generations, changes in pollution signatures for specific protected areas can be identified, acting as an early warning system for rising levels of certain pollutants. Given the complex physiological, ecological, environmental and biological processes involved in eco-toxicology assessment of protected areas, it’s essential to implement pro-active wildlife management frameworks and strategies to monitor these changes and ensure ecosystem integrity.
There is increasing evidence to demonstrate that low-level exposure to potentially toxic elements, above-or-below optimal level intake of essential elements and exposure to mixtures of either, or both in combination with other chemical substances can lead to multiple negative effects. In humans, the links between EDCs and compromised thyroid, metabolic and reproductive function are clear, but effects in free ranging wildlife species are currently understudied and may be a contributing cause of under diagnosed conditions affecting wildlife reproductive ability and survival.
Andrea Webster is a postdoctoral researcher with the University of Pretoria’s Mammal Research Institute. Current research is partially funded by the Oppenheimer Chair for Emerging Scientists in Non-invasive Wildlife Research Programme and aims to examine predator-prey interactions between brown hyaena and black backed jackal to better understand their influence on meso-herbivore recruitment rates. Her research combines non-invasive methods with behavioural endocrinology, ecotoxicology and predator ecology to address environmental health and wildlife management issues.
Her publications include: