Something very strange is happening in a favorite crocodile haunt, the Olifants Gorge, in South Africa's Kruger National Park. Crocodiles are dying en masse, and a local television documentary has showed, recently, the many carcasses floating in the river or lying dead in the sun on the river bank.

In the month of June alone, 30 carcasses were counted in the Olifants River area alone. This figure has subsequently risen to 50.

Old Crocs Susceptible

Most carcasses appear to have distinctive discoloration in the tail's fat tissues. The tissue is a mustard yellow color, and unusually hardened. Scientists seem to be finding a higher mortality among the older crocs. What appears to happen is that the crocodiles, in attempting to fatten themselves up over winter, have had their fatty tissues poisoned, and the chemical reaction which hardens these tissues gradually paralyses them in what is likely an excruciating death.

Kruger National Park's Head of Department for Scientific Services, Danie Pienaar suggests the crocodiles are afflicted with pansteatitis. But this disease is associated with ingesting rotten fish, and the fish in the Olifants River are apparently healthy.

Unholy Mix of Manmade Gunk

There is growing consensus that the croc die off is as a result of a confluence of low level toxins which has lead to endocrinal abnormalities (that is, hormonal changes) in croc tissues.

The spokeswoman for the Kruger National Park and the Water Research Commission, Linda Page, has cited traces of 15 pesticides in local river water, and indicated while the levels of these were below WHO drinking water guidelines, she said they were [also]" the range where possible accumulation in the food chain is possible."

Indecent Exposure

Long term exposure to these and other toxins may well be conspiring towards the crippling condition suffered by Olifants River crocodiles. But other pollutants have also been discovered in the water, phthalates for one. Phthalates, related to plastics, have been found in both sediments and water samples. The phthalates may account for the hardening of fatty tissues.

Despite reasonably transparent river water (no algae), polyaromatic hydrocarbons have also been found at higher than normal levels in sediments. These are related to local grass fires and coal combustion, the latter having increased dramatically in recent times.

Dam Impact

The construction of the Massingir Dam may also have promoted long term exposure and accumulation to these various compounds, especially since it is in the nature of dams to promote not only a buildup of water but the sediments carried in the water.

Warren Foster, writing for the Mail & Guardian opines: "The expansion of mining in the area, compounded by the withdrawal of water by a dam in Mozambique, is seen is a possible cause."

Unexpected Surprises

What is interesting and distressing about this case is that we see here a combination of chemicals which has formed a mixture in river water lethal to crocodiles. Separately each compound has been introduced into the river system at apparently low and safe "healthy" levels.

It is this sort of unexpected, ongoing (and as yet, unexplained) mass die off, associated with human development and human activity, that should provide human beings with additional warning as we move further, making all those demands that we do on the environment, into the unknown. We approach the future -- towards climate change, and a fossil fuel crisis (during which we will undoubtedly turn to the worst polluter of all, coal) -- unlocking ever more destabilising processes that are a result of our ill-considered activities.

While in this case crocodiles are the obvious victims, no one knows what impact (long term or short) the sick water of the Olifants River might have on human beings exposed to it. Meanwhile, at least 18 platinum mines continue to operate in the Kruger Park's water catchment areas.