South Africa’s leading researchers, scientists, conservationists and wildlife pathologists have joined forces under a new programme dedicated to answering the perplexing questions surrounding the death of hundreds of crocodiles in the Kruger National Park’s Olifants gorge. The initiative, known as the Consortium for the estoration of the Olifants Catchment (CROC) at present, will be led by ANParks. It also includes representatives from national government departments, including the Departments of Water Affairs & Forestry and Environmental Affairs & Tourism, research organisations, universities, independent consultants, and the Water esearch Commission.
The programme was initiated after it became increasingly clear that the death of the crocodiles was symptomatic of a serious and growing environmental problem in the Olifants River system. The river has been subjected to prolonged and cumulative ecosystem stress as a result of human activities in the catchment, which is thought to have resulted in the deaths of many of this top predator. “Next to the Vaal and the Crocodile West rivers, the Olifants is probably South Africa’s hardest working river,” reports aquatic ecologist Dr Peter Ashton of the CSIR, who is also part of the programme. “The river has been used and abused for the past five decades, and pollution is getting progressively worse. This can be seen in the character of the water quality, which has worsened markedly over the years.”
While clues are increasingly pointing to pollution from industrial, mining and agricultural sources as well as the alteration of the Olifants River system through bulk water infrastructure (such as the raised water level in Massingir Dam), the exact trigger that started the process of crocodile deaths remains elusive. This is one of the first questions the programme hopes to answer through multidisciplinary research. Direct poisoning from, for example, persistent organic pollutants and heavy metals, has already been eliminated as the direct cause of mortality.
While no direct threat has been found yet, there is also increased concern over the potential effect of pollution on the health of communities residing in the Olifants River catchment, especially those households still using untreated water from the river. This will also be investigated by the programme. Crocodile carcasses were first spotted in the Kruger National Park in May this year. To date, at least 160 carcasses have been found, although the actual number of deaths is estimated to be at least double this figure, as crocodile carcasses sink quickly or are consumed by other crocodiles and are then missed. Post-mortem results show that the crocodiles died of pansteatitis, a disease which results in the general hardening of the body fat, mostly as a result of inadequate antioxidant levels (e.g. Vitamin E).
The hardened fat causes the crocodiles to ecome stiff which results in reduction in mobility and the inability to swim. This leads to starvation and even drowning of the affected animals. This is not the first time crocodiles have died in the Olifants River system (crocodile mortalities also due to pansteatitis have also been reported in Loskop Dam), although the massive die-off of Kruger crocodiles did catch authorities unaware. “We suspected that the ongoing pollution of the Olifants River system would eventually result in some kind of ecological disaster. The large number of crocodile mortalities, however, caught us by surprise,” notes Danie Pienaar, Head of the Department for Scientific Services at the Kruger National Park.
“One of the important outcomes of this programme will be to put in place a rapid response management mechanism should something of this nature ever happen again.” While rangers are still finding sporadic cases of dead crocodiles, the number of mortalities has slowed significantly recently. This could perhaps be attributed to management actions, such as the removal and burning of carcasses to prevent cannibalism. How the mortalities will affect future population numbers remains to be seen. Meanwhile research into crocodile population dynamics, which involves fitting of radio transmitters on surviving crocodiles to track movements, as well as studies of other aquatic species in the river system continue. The quality of the water in the Olifants River is also being monitored closely.
As the Olifants is a transboundary (i.e. shared) river system, active cooperation is being sought with Mozambican authorities. SANParks Honorary Rangers’ Rangers Support Services Group have donated two boats to the Kruger National Park, one to be used for law enforcement, monitoring and research on the South African side, while the other will be lent to the Limpopo National Park in Mozambique to be used for the same purposes downstream in the Olifants River.
Pansteatitis is usually associated with the consumption of rotten and rancid fish. However, no confirmed fish mortalities were observed in the Olifants gorge. Recent investigations by independent fish pathologist Dr David Huchzermeyer indicated that most of the fish caught in the gorge are not healthy and that their internal organs and gills are affected. This is symptomatic of exposure to toxic agents. It is hoped that the outputs from this programme will not only benefit the communities and wildlife dependent on the Olifants River system, but will lead to the improvement of the management of South Africa’s other river systems to prevent such ecological disasters occurring in future and an overall improvement in river health.
Compiled by: Lani van Vuuren
Public Understanding of Science Officer, Water Research Commission
Tel: (012) 330-0340; E-mail: email@example.com
For more information:
Mr Danie Pienaar
Head of the Department for Scientific Services at the Kruger National Park
Tel: (013) 735-4148