Killer hippo poo is enemy number one

Published Aug 5, 2007

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When the carcasses of lions, zebras, white rhinos and other animals began to be discovered alongside some dams in the Kruger National Park, experts were at first puzzled.

Now hippo faeces and urine have been declared enemy number one. As a result, engineers plan to breach the walls of the Nhlanganzwane dam in the south-eastern section of the park on Monday forcing hippos, which have been concentrating there in large numbers, to take up fresh abode.

Dr Jan Myburgh, a toxicologist at Pretoria University's faculty of Veterinary Science (which works closely with Onderstepoort) said they had investigated four dams near Crocodile Bridge in the Park.

He explained that large quantities of sewage flowing into rivers often resulted in high levels of fertiliser such as nitrogen and phosphorus in the water.

This, in turn, led to eutrophication - the formation of microcystis, a harmful blue-green algae.

Myburgh explained that an over-population of microcystis bloom was very toxic and could cause liver failure.

He said reports began to filter in of the carcasses of animals being found close to dams, but these displayed no signs of predation. What vets began to notice, though, was a green scum on the water.

"We tested the water to identify the organism and also tested for toxicity and found it was very high. The pathologist confirmed the same with some of the carcasses."

Although most of the bodies were old, about two weeks ago a fresh zebra carcass was found. From this scientists were able to confirm liver failure. As no detergents or sewage flowed into the Kruger dams, they began to suspect a direct link with the hippos.

"We also noticed that in a certain area after a veld fire, the resident hippos moved away from that dam. After that the bloom (algae) went away. So it appeared there was a direct link to hippo defecating in the water," said Myburgh.

Microcystis is usually particularly active in summer and has low activity in winter. "But in Kruger it was the reverse," said Myburgh. "In winter the animals concentrate in certain dams."

Heavy rain dilutes any nitrogen and phosphorus in the water and algae thrive in alkaline water which is warmish - cooler, running rivers are not conducive to the algae.

The problem was first picked up about two years ago, but as it was sporadic at first nobody took notice of the dead animals.

"Then in 2006 they realised a pattern was emerging," said Myburgh.

If funding were forthcoming, other dams would be monitored for algae levels.

"As rain falls and the rivers start filling up the hippos will move into these automatically," said Myburgh.

According to SanParks spokesperson Raymond Travers the option of fencing the dam was impractical as herds of elephants were likely to stampede any such structure and the hippos could also try to return at a later stage. - Additional reporting by AFP

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