Durban - The surprise discovery of rhinos with bright pink lips and swollen eyes in northern KwaZulu-Natal has raised alarm bells over the potentially devastating spread of an alien invader plant which can kill cattle and decimate the fields of peasant farmers.

Internationally respected conservationist and environmental consultant Professor Ian Macdonald, who photographed the two adult black rhinos in Phongolo Game Reserve recently, said he was shocked to notice the lips and nostrils of both animals had turned bright pink, while their eyes and eye sockets were “puffed up like Popeye” – apparently from eating an invader plant known in Ethiopia as “famine weed”.

Macdonald, the former chief executive of the World Wildlife Fund (South Africa), said both animals were seen browsing in a dense stand of Parthenium hysterophorus, a highly invasive alien plant from Central America and the Caribbean.

“Parthenium is the worst invader plant I have ever come across,” said Macdonald, who has advised several governments on how to deal with alien weed infestations.

He also warned the rapid spread of parthenium into northern KZN via Swaziland was not only a threat to wildlife and indigenous vegetation, it could have major implications for the survival of subsistence farming communities.

Macdonald said a high percentage of people who came into contact with the weed developed allergic reactions such as skin problems, hay fever and asthma. The International Union for the Conservation of Nature has reported isolated human deaths in India linked to the weed. There are also several research papers documenting the death of cattle and water buffalo as a result of eating the plant.

He emphasised further research was needed to demonstrate conclusively whether the weed was harming rhinos and other wildlife in South Africa.

“The symptoms of allergic reactions we saw on these rhinos have not been proven yet, although we know that parthenium is spreading at a fantastically fast rate in northern KZN and we also know that people and animals in many parts of the world show allergic reactions from exposure to it… I will never touch these plants with my hands, and Ezemvelo KZN Wildlife’s emergency weed-control teams wear gloves and overalls when handling it.”

Macdonald said he came across the pink-lipped rhinos in March during an alien-plant survey with his research assistant, Jan Lee. To avoid close contact with the potentially aggressive beasts Macdonald took photographs from a distance and it was only when they returned to the office and magnified the digital pictures that they noticed the possible evidence of allergic reactions.

“We were horrified to see that both had bright pink lips and pink stripes around the nostrils. Their eyes and the eyesockets were also inflamed.”

Macdonald said he showed the pictures to Dr Peter Ardington, the former president of the SA Veterinary Council and former game rangers Paul Phelan and Peter Hitchins, none of whom had seen such vividly-pink lips in rhinos before.

They were also surprised as black rhinos are able to browse from highly toxic indigenous plants like candelabra euphorbia.

“Maybe they have evolved to tolerate the toxic latex from indigenous plants but not alien plants from other continents. This has given some people an enormous fright and so we raised the alarm – but there are no other indications that the weed is causing anything more serious than what we have seen so far.

“I think politicians need to wake up to this threat as subsistence farming will become non-viable. You simply can’t control this weed on a peasant’s budget,” he said, noting that even expensive chemicals were not effective in eradicating the alien pest.

“In Ethiopia it’s known as ‘famine weed’ because peasant people know they are finished once it starts spreading. They form parthenium deserts. This is an amazing weed as it can move from seeding to flowering in four weeks.”

Macdonald said he came across three plants on the side of the road in Mkhuze Game Reserve during a survey earlier this year. Nine weeks later there were “thousands” at the same spot.

The Ndumo and Phongolo reserves were the worst affected protected areas, although dense infestations had also been seen around Nongoma, Ulundi, Imfolozi, Mtubatuba and Hluhluwe.

There was also evidence that the weed exuded allelopathic chemicals into the surrounding soil that inhibited the growth of other plants.

Macdonald said although medical colleagues had not reported any cases of people getting sick from parthenium in KZN he had heard unverified reports of two conservation staff being hospitalised after pulling up some weeds from the roadside with bare hands. - The Mercury