The pansteatitis pollution that turned Nile crocodiles to rubber
In May 2008 rangers at South Africa’s Kruger National Park found a devastating sight in the Olifants Gorge.
The gorge, which is usually a haven for giant Nile crocodiles, was littered with their dead bodies.
Over the next few days more than 30 dead crocodiles were found with their bodies turned to rubber. The corpses had no signs of injury and the rangers were utterly baffled as to how these resilient creatures could die so suddenly.
The rangers started an investigation to find out why so many crocodiles were mysteriously dying in the river. What they found was a truly shocking example of how humans have caused terrible effects on the natural world.
The investigation into why so many crocodiles died was made into a documentary called The Crocs That Turned To Rubber. This t followed the team of rangers at Kruger National Parkas they set about trying to solve the mystery of why the crocodiles were dying so rapidly.
Park authorities launched an investigation into the mysterious deaths which was led by ecologists Danie Pienaar and Dr Danny Govender.
After conducting post-mortem examinations on some of the dead crocodiles, the team realised that a disease known as pansteatitis was behind the mass die-off.
When they cut open the dead crocodiles they realised that their insides were consumed by an orange, really hard, really rubbery fat. They recognised this is pansteatitis. It resembled a thick rubber.
Pansteatitis is more common in domestic cats. The disease is caused by a combination of consuming too much rancid fat and a lack of vitamin E. The condition causes fat to solidify leaving infected creatures lethargic, heavy and unable to hunt, eat, or defend themselves.
Once pansteatitis had set in, the crocodiles were unable to move. Their limbs were jammed solid and they died. This condition is fatal for crocodiles that rely on being lightning fast to snare their prey.
A crocodile was soon spotted in the park feeding on the corpse of another crocodile. The crocodiles had turned to cannibalism and the only method of stopping the disease from spreading in this way, and potentially into land predators such as lions, was to remove all the corpses from the gorge.
The park team started a massive clean-up operation by winching the 200kg corpses out of the gorge by helicopter and burning them all. This prevented other crocodiles from feasting on dead bodies and contracting the deadly illness pansteatitis
The move had a positive effect on crocodiles in the gorge and for several months no deaths were recorded.
But the rangers had still not discovered the reason behind the deaths. They carried out tests on the water which came back fine. And they even questioned local poachers which they thought might be leaving dead fish in the water which crocodiles were then eating.
And it was no surprise when next season the team had another setback when pansteatitis returned to the gorge. Another mass die-off claimed the lives of 179 crocodiles.
Two months later a spate of fish deaths occurred and this time the fish were discovered to be carrying the same disease. The dead creatures were all African sharp tooth catfish – a favourite food of crocodiles. Catfish feed on the bottom of the river which led the experts to suspect that pollution might be the cause of the crocodile deaths in Kruger National Park.
The only thing that coincided with the deaths was the opening of the controversial Massingir dam 20 miles downstream and across the border in Mozambique.
When the dam opened,water levels in the gorge rose by about 20metres and the flow of water was slowed. The gorge was also flooded with a fine, sticky silt that clogged the water.
No one chemical in the water was strong enough to kill the crocodiles. But ecologists found around 1,500 toxins in the water with most of them coming from unregulated mining and sewage disposal from large industrial plants and factories in nearby towns. These toxins when combined with increased silt levels created a toxic soup. The catfish feed on the heavily polluted silt and in turn they are fed upon by the crocodiles which spreads the fatal disease.
To this day rangers have been unable to stop the spread of pansteatitis which has steadily killed off huge numbers of crocodiles. The population of Nile crocodiles in the gorge is expected to have been totally killed off in the next 20 years.
What's worse is that Krugar National Park relies partly on tourists visiting the area for revenue - and fewer people are likely to go if there aren't any crocodiles to see.
The deaths of the crocodiles is a sad story of how humans are damaging wildlife and the natural world with pollution. The pollution comes from business and humans' need to make money.
The last thought to finish with is something that one of the rangers said. ''Crocodiles have been in the gorge for 200 million years...and in just two years humans have almost wiped them out here.''
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