Lack of Antioxidants Cripples and Kills South African Crocodiles.
Overutilisation and pollution of the Olifants River System in northeastern South Africa is suspected to be implicated in the death of hundreds of Nile crocodiles in the Kruger Park while too low a level of antioxidant is directly associated with the deaths.
The Nile crocodile, the species found in South Africa, is part of an ancient lineage and has changed little in the 65 million years since the dinosaurs with whom it coexisted became extinct.
With an average mass of 550 kg, covered in heavy scales, awkward on land and totally reptilian, it is difficult to see their link to panda bears. But in the 1960s both were endangered species. Since then crocodile farming has become established and is booming with sales of around 150,000 Nile crocodile skins a year. This has made large scale hunting for hides a thing of the past and as a result the pressure has lifted and there are now between a quarter and a half million crocodiles in the wild in Africa.
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But in South Africa at present there is concern about the large numbers of crocodiles which have died in the Kruger Park over the last several months - a total of 160 to date. The death rate is currently declining but the concern is that the actual cause is still unknown.
Postmortems have shown that the direct cause of death is pansteatitis, which results in the general hardening of the body fat. Pansteatitis is mainly a result of inadequate antioxidant levels (e.g. Vitamin E) that would normally prevent peroxidation of the fat. Hardened fat causes the crocodiles to become stiff which makes them less mobile and eventually unable to swim. This normally leads to them starving to death or drowning.
Cases of crocodile deaths have been recorded previously where chemical pollution has promoted the growth of algae which depleted the water of oxygen and killed fish. Eating these decayed and rancid fish caused pansteatitis in the crocodiles. However, there has not been mass fish deaths in the area and the trigger of the pansteatitis has not been found.
It has become increasingly clear to those involved, that the death of the crocodiles is symptomatic of a serious and worsening environmental problem in the Olifants River system, which is a consequence of human activities in the catchment. The Consortium for the Restoration of the Olifants Catchment (CROC) has been set up to study the Olifants River system with one of the prime objectives being to establish a link between water quality and the death rates of crocodiles.
Danie Pienaar, Head of the Department for Scientific Services at the Kruger National Park said “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.”
The current situation in South Africa is also quite different from the case posted by Jennifer Lance in Ecoscraps where crocodiles in Australia are dying from eating poisonous frogs and in India where rare gharial (a unique species of crocodilian) seem to be dying from kidney failure resulting from high toxin levels in the Yamuna river.
By the way I have no idea why scientists and researchers can’t resist these weird acronyms - CROC? Really!
Photo Credit: By tai strietman on Flickr under a Creative Commons License
It is encouraging to be able to learn of the multiple research and remedial efforts on behalf of this animal and the river system which is its habitat. Thank you for the article.