Poisoned Chalice: Study Reveals Impact of Transformed Landscapes on Carnivores and Environment

The transformation of natural landscapes for human use, such as agriculture and urbanization, has been linked to increased concentrations of persistent organic pollutants (POPs) in wildlife. A recent study published in Science of The Total Environment has found that caracals (Caracal caracal), medium-sized wild cats native to Africa, living in transformed landscapes had higher concentrations of POPs in their blood than those living in natural habitats (1). The study also found that the accumulation of POPs was associated with potential immune effects, highlighting the impact of environmental pollution on wildlife health.

A recent study has found that caracals, medium-sized felids native to Africa and the Middle East, in and around Cape Town, South Africa are exposed to harmful environmental pollutants associated with human activities. The study focused on toxic organochlorines (OCs), including dichloro-diphenyl-trichloroethane (DDT) and polychlorinated biphenyls (PCBs), which are known to have negative effects on wildlife and human health. The results of the study showed that exposure to OCs was widespread in the caracal population in the region.

The study analyzed the blood and adipose tissue of 69 caracals, along with detailed spatial, dietary, demographic, and physiological data. The analysis revealed that the detection rate of PCBs was 100% in blood and 100% in adipose tissue, while the detection rate for DDTs was 83% in blood and 100% in adipose tissue. The study found that caracals using human-transformed areas, such as vineyards and areas with higher human population and electrical transformer density, as well as wetland areas, had higher organochlorine burdens. These landscapes were also highly selected foraging areas, indicating that the caracals are drawn into areas that increase their risk of exposure to these pollutants. Further, biomagnification potential was higher in individuals feeding on higher trophic level prey and on exotic prey, which suggests that caracals feeding on higher-level prey or introduced prey had higher organochlorine burdens.

The measurement of environmental pollutants such as organochlorines in animal tissues typically involves a process called "biomonitoring." Biomonitoring involves the collection and analysis of biological samples, such as blood, urine, or adipose tissue, to assess an individual's exposure to chemicals. The measurement of these pollutants in the samples typically involves a variety of analytical techniques, including gas chromatography-mass spectrometry (GC-MS) and/or liquid chromatography-mass spectrometry (LC-MS). These techniques allow for the detection and quantification of specific chemicals in complex biological matrices, such as blood or adipose tissue.

The study also revealed possible physiological effects of exposure, including an elevated white blood cell and platelet count, which could increase the caracals’ susceptibility to disease. The researchers suggest that the urban fringes of Cape Town, which are particularly toxic areas to wildlife, are a source of toxic chemicals for the caracals and require focused attention and action to ensure the persistence of this adaptable mesocarnivore. The caracals play a vital role in the ecosystem, and as they are at the top of the food chain, they can act as useful indicator species for understanding the spatial and dietary predictors of these contaminants.

The study highlights the severity of exposure to environmental pollutants associated with human activities in wildlife and emphasizes the need for pollutant control. The research suggests that understanding the spatial and dietary predictors of these contaminants can inform policies that can help reduce exposure risk. The caracals are an important part of the African ecosystem, and their exposure to harmful environmental pollutants can have a ripple effect throughout the food chain. It is crucial to take action to ensure the persistence of the caracal population and maintain ecosystem stability.

Reference

(1) Leighton, G. R.; Bishop, J. M.; Camarero, P. R.; Mateo, R.; O'Riain, M. J.; Serieys, L. E. Poisoned chalice: Use of transformed landscapes associated with increased persistent organic pollutant concentrations and potential immune effects for an adaptable carnivore. Sci. Total Environ. 2022, 822, 153581. DOI:10.1016/j.scitotenv.2022.153581