Tue, 23 Jul 2019

There are fresh fears for the future of the Cape Peninsula's caracals following a study showing widespread exposure to rat poisons.

Dr Laurel Serieys, a scientist who specialises in studying the city's caracals, sampled the livers of 24 cats.

Serieys is a postdoctoral researcher at the University of Cape Town's Institute for Communities and Wildlife in Africa and coordinator of the Urban Caracal Project.

Her team tested a variety of species for common rat poisons and found widespread exposure across all species, but caracals were the worst affected with 92% exposed.

Serieys has studied rat poison exposure in wildlife since 2006 and it was the topic of her PhD work at the University of California in Los Angeles, where she documented poison exposure in bobcats and mountain lions.

The results were very similar to what she found in caracals in Cape Town.

"So the results were not surprising. But when you stack it on top of all the other threats to caracals in the Cape Peninsula, then it is concerning to see such high exposure rates to this particular pesticide," she told News24.

Serieys linked at least two deaths directly to rat poison, but said even though the cats may not die instantly there are many insidious effects on their health.

The poison can slowly compromise their immune systems and reproductive health over time, ultimately leading to population decline.

"Although we didn't find a lot of animals that died directly due to rat poison exposure, finding so many animals that were exposed to rat poisons means that the compounds are very pervasive in the local ecosystems. And if enough species are exposed to these common rat poisons, then it could potentially lead to population declines and alter ecosystem function in the Cape Peninsula," she added.

"Another interesting finding from this study is we found kittens were already exposed to the poisons and from my work in the United States, I know that even animals that are still in the womb can be exposed to these rat poisons and accumulate the compounds in their livers.

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"So, when you think about an animal being exposed to some - even if it's a low level of poisons - for the duration of its entire life, beginning from before it's even born, then it raises questions about the consequences for wildlife," she said.

Serieys said she documented population declines in bobcats - a species that's very similar to caracals - as a result of exposure to the poisons weakening their immune systems and making them vulnerable to other diseases they would normally be able to withstand.

She added that these poisons have also been linked to reproductive effects in humans and laboratory rats, which suggests the cats may also suffer birth defects or other fertility issues.

A long list of threats

When adding poison exposure to the long list of other threats the animals face in the urban environment, the long-term outlook does not look good.

"In the past month, we've documented five deaths for caracals just within the Cape Peninsula and what's alarming about this is that we estimate that the population size is only about 50 caracals in the entirety of the Cape Peninsula... and so assessing the impact to the population is not trivial, when you're looking at so many dead caracals piling up in such a short time frame."

Serieys says she hopes the study will help educate the public about the unintended consequences of using rat poisons and encourage more people to look at alternative means of pest control.

"It's something that as individuals we can make a choice whether or not we use these poisons. We can't easily prevent people from driving on roads and hitting animals with their cars, but as an individual we have the option to choose a more sustainable way to live with wildlife that lives near the urban boundaries."

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