Rat poisons threaten SA’S wildlife

SHEREE BEGA

URBAN rat poisons are spilling over into Cape Town’s natural environment, threatening species such as caracal, mongoose, otter and owl, a team of UCT researchers has found.

In their recent paper, published in the journal Science of the Total Environment, the researchers from the Institute for Communities and Wildlife in Africa (icwild) discovered anticoagulant rat poisons were infiltrating Cape Town’s peri-urban wildlife food chains.

The study was conducted within and around Cape Town’s Table Mountain National Park.

These animals already face challenges that include habitat loss, vehicle collisions, poachers and fire, said lead author Dr Laurel Serieys, a postdoctoral research fellow at the icwild.

They identified six predator species at risk: caracal, Cape clawless otter, Cape eagle owl, large spotted genet, honey badger and water mongoose. Others were likely affected as well. The study measured the presence and concentration of rat poison compounds in liver and blood samples from 41 animals. At 92%, exposure to rat poisons was highest for caracal. Overall, they found 81% exposure across seven species tested.

The predators aren’t eating the poisons directly. Rather, the poisons are designed to work slowly in their target species, rats, who become sick over a period of days and end up as easy prey for predators.

“We detected at least one of the four most toxic rat poison compounds, all available in over-the-counter products, in six of the seven species tested,” says Dr Jacqueline Bishop, lead supervisor on the project.

Caracals living in or near vineyards had the highest exposure to rat poisons but the route to exposure is unclear. “Vineyards in Cape Town don’t use rat poisons, but they do host restaurants, spas and occur adjacent to dense residential areas where rat poisons are used,” she said.

The fact that the animal tested use different habitats shows that rat poisons may impact many species.

“It also suggests, in the case of otters, that polluted water run-off from urban areas could transport the poisons into Cape Town’s waterways and the aquatic food chain,” said collaborator Dr Nicola Okes.

Several lactating female caracals were sampled in the study and found to be exposed to rat poisons, suggesting that kittens may be exposed through their mothers’ milk.

“As consumers, we need more ecofriendly alternatives to rat poison and the simplest solution is well within everyone’s reach – improve the management of waste which attracts rats,” said the researchers.