Crocodile fatalities in one particular stretch of the Olifants River are baffling local and international scientistsKruger National Park authorities and scientists are racing against the clock to identify the cause of a disease killing some of the reserve's crocodiles.Thirty crocodiles living in the park's Olifants River gorge — the biggest breeding ground of Nile crocodiles in Southern Africa — are expected to die within weeks. At least 15 have died since last month. Last year, 170 died.And park officials fear that the remaining 385 reptiles in the gorge, which is close to the Olifants River rest camp, could be wiped out within three years unless a cure is found.The park — the country's biggest tourism draw card, attracting more than 1.3 million tourists annually — South African National Parks, the Department of Water and Environmental Affairs, the Council for Scientific and Industrial Research, research organisations and the universities of North West and the Free State have formed a steering committee to discover the cause of the crocodile deaths. They have also urgently approached environmental chemists in Norway and Sweden for assistance.This week, a team from the Sunday Times accompanied two rangers and Kruger Park spokesman Raymond Travers on a boat trip along the last 15km of the gorge before it crosses into Mozambique.Although several crocodiles that were basking on the banks swam off as the boat approached, others could barely move, even as the rangers came within 1m of them. Many were emaciated and could only make feeble efforts to escape when the rangers tried to capture them.Watching a three-and-a-half metre crocodile move very slowly into a shallow pool on the river bank, Evans Mkansi, the section ranger for the Olifants River gorge area, said: "He will die very soon. His slow reaction is a sign that he's very sick."Mkansi burnt 14 crocodile carcasses last month.Another crocodile — one of four fitted with a transmitter in May to monitor its movements — was also close to dying, according to Mkansi. "It's very sad to see them in this state. At least 30 are very, very sick and will die soon," he said, almost overcome with emotion.During the trip, Mkansi and field ranger Thomas Macie destroyed four gill nets, measuring more than 100m in total, which had been placed in the river by poachers from Mozambique. They later burnt 110 tiger fish that had become ensnared.Experts have partially blamed the deaths on the raising of the Massingir dam wall in Mozambique, about 30km upstream, because it causes accumulation of sedimentation as a result of the river no longer flowing freely.Also believed to contribute is pansteatitis, a hardening of the fat in the crocodiles' tails and abdomens that results in them becoming immobile.It is caused by the reptiles eating dead fish.But University of the Free State biochemist Professor Garry Osthoff, who analysed the fat samples in 12 crocodiles, believes it is difficult to blame the dead fish as the main cause of the crocodile deaths.He said his research had so far not pointed conclusively to a direct link between the two.Travers said researchers locally and abroad had analysed water, sediments and fish and crocodile tissue samples for potential toxins and chemical compounds."Although many heavy metals, agricultural pesticides and organic waste were detected, none were found to be above the levels where adverse effects are expected. None were individually responsible for poisoning the crocodiles."Professor Henk Bouwman of North West University confirmed that none of the chemicals found in the water could have individually caused the deaths of the reptiles.He said they were baffled why only crocodiles living in the gorge were dying.Peter Ashton, the CSIR's principal researcher in the natural resources and environment department, said there was a possibility that some or different sources of contamination in the upper catchment area may be responsible."Since mining activities occur over large parts of the Olifants catchment, there is a possibility that mining activities may be implicated, but there is no definitive proof of this link."He said treated and untreated sewage effluent from mining, industry, agriculture and urban activities, containing high loads of faecal bacteria, might also be responsible.thetimes.co.za
No comments:
Post a Comment