view more
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 analysed liver samples from 102 caracal mortalities collected over ten years, mainly from car collisions, revealing highly toxic anticoagulant rodenticides (ARs) in 78% of samples analysed. 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 caracal 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 from clotting. They work by blocking vitamin K cycle in the liver, causing fatal internal bleeding in target rodents as well as non-target mammals and birds that are 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 the animal’s tissues for 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 non-target predators and scavengers.
