This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Rat poisons used in homes, businesses and on farms are moving into South Africa's wildlife, according to new research from the Urban Caracal Project, a key research and education initiative based in the Institute for Communities and Wildlife in Africa (iCWild) at the University of Cape Town, together with international collaborators from the Institute for Game and Wildlife Research (IREC) and the Institute of Environmental Assessment and Water Research (CSIC) in Spain. In the paper, published in Environmental Pollution, researchers analyzed liver samples from 102 caracal mortalities collected over 10 years, mainly from car collisions, revealing highly toxic anticoagulant rodenticides (ARs) in 78% of samples analyzed.
Most individuals were exposed to at least three different compounds, but some were found to have up to six compounds in a single sample. Older animals had higher burdens, supporting the study's conclusion that caracals experience repeated, long-term cumulative exposure to ARs in the study area. The research found that highly toxic second-generation compounds dominated the population's exposure profile.
Anticoagulant rodenticides are chemical poisons that inhibit blood clotting. They work by blocking the vitamin K cycle in the liver, causing fatal internal bleeding in target rodents as well as nontarget mammals and birds exposed to lethal doses. First-generation ARs generally require repeated feeding and break down faster in animal tissues, while more commonly used second-generation products, or SGARs, were developed in the 1970s partly to overcome resistance to older poisons.
SGARs are more potent, can be toxic after a single feeding and remain in an animal's tissues longer. However, even a toxic dose can take a while—up to two weeks—to kill a poisoned animal. Because death is delayed, rodents may continue feeding and carry high concentrations that subsequently poison nontarget predators and scavengers.
"Caracals are red warning lights at the top of the food web," said Dr. Gabriella Leighton, the lead author and currently a lecturer at Stellenbosch University's Department of Botany and Zoology. "Caracals move easily through natural areas, farms and suburbs and eat many kinds of prey.
What accumulates in their bodies provides a broader picture of contamination across the landscape." While felid species such as caracals are highly tolerant of exposure to ARs, such that they rarely die from exposure, the authors stress that "the sublethal effects of ARs are currently unknown for caracals." However, subadult caracals in poorer condition carried higher loads. As apex predators in the urban food web, caracals are valuable indicator species: animals that reveal wider environmental contamination. Previous research by the Urban Caracal Project also documented AR exposure in other carnivore species in and around Cape Town, including otters, large-spotted genets, mongooses, honey badgers and owls.
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