Rat poisons killing more than just rodents, study says

Wildlife predators that prey on rats in Cape Town may not live long enough to tell the tale.

A new study by the University of Cape Town’s Institute for Communities and Wildlife in Africa found that rat poisons have made their way into the food chain in the Table Mountain National Park.

“We detected at least one of the four most toxic rat poison compounds … in six of the seven species tested,” said Dr Jacqueline Bishop, lead project superviser.

The species at risk are the caracal, Cape clawless otter, Cape eagle owl, large spotted genet, honey badger and water mongoose, all of which are being poisoned by preying on rats that have ingested the toxic compounds.

These animals already face increasing habitat loss as well as threats from vehicle collisions, poachers and fire, said lead author Laurel Serieys, a postdoctoral research fellow at the institute.

Researchers found that caracals, particularly those living in or near vineyards, had the highest exposure to the poisons, at a rate of 92%. Overall, they found 81% exposure across seven species tested. 

“Vineyards in Cape Town don’t use rat poisons to protect their vines,” Bishop said. “Caracals regularly hunt in vineyards and it is here that they are likely to be exposed to poisoned rats.”

The study measured the presence and concentration of rat poison compounds in liver and blood samples from 41 animals, with a special focus on caracals as part of the Urban Caracal Project. 

The poisons affect animals of all ages and different habitats. Though the poisons' definitive route has not been established, caracal kittens could be exposed through their mothers’ milk, and otters may encounter the poisons when waterways are polluted.

“As consumers, we need more eco-friendly alternatives to rat poison,” the study concluded.

“The simplest solution is well within everyone’s reach – improve the management of waste which attracts rats in the first place.”