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Mass deaths of South Africa's Nile crocodiles puzzle biologists
October 9, 2009 | 9
The Letaba River was one of the sites of crocodile deaths in 2008, and to try to find the killer, researchers rushed to the scene to collect, remove and dissect carcasses, which were found washed ashore or simply floating....[More]
This year, researchers and park staff found 23 Nile crocodiles dead of the mysterious ailment in the Olifants River by August 7. Reports came in at the end of the month of two more dead in the nearby Sabie River, another Kruger National Park river, which flows into Mozambique....[More]
Rangers from Kruger National Park remove as many croc carcasses as possible, sometimes flying the bodies out of range of other crocodiles that might cannibalize their fellows and thus potentially expose themselves to deadly toxins....[More]
Rangers burn crocodile carcasses in funeral pyres like this one in 2008. By November last year, 170 crocodiles had been found dead.
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Researchers and park rangers flew into a gorge along the Letaba River in Kruger National Park in July 2008 to dissect a dead Nile crocodile.
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The sick and the dead crocodiles have hardened yellow fat deposits, indicating a possible stress response to a toxic substance. Fish in the river showed the same, a condition called pansteatitis.
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Ecotoxicologist Henk Bouwman of North-West University, Potchefstroom (South Africa) straddles a live croc while taking samples from the animal for testing....[More]
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9 Comments
Add CommentThis is just another 'dot' that is connecting to more 'dots' that's making a puzzle picture of the distruction that man is wreaking across the globe. Someday as a race of beings we may figure out that we need to be 'a part' of nature and work in harmony with all the other life instead of being 'apart' from it and thinking we can take what we want and rule the world with no consequences. My fear is that day may come too late for most.
Reply | Report Abuse | Link to thisChuck Norris is killing those crocs.
Reply | Report Abuse | Link to thisI am sorry but sometimes I want to shake those ASSHOLES off until they see what they have done and make them understand responsibility they had ruining our ecosystem! Only why - I have sitting in my mind do we have to watch and experience consequences of what these (normally it comes to one or couple of people who make the decision... and of course those followers who are too scared to say no and not act upon the evil commands they are given!!) did. We are gonna die all! first by destroying ecosystem around us and then suffering from what was done! I very much hope we all get awaken sooner than when it is too late!
Reply | Report Abuse | Link to thisRead "The Culture of Make Believe" and "Endgame" by Derrick Jensen. It will be like waking up...all the way.
Reply | Report Abuse | Link to thisHow the heck does Chuck Norris come into the equation?
Reply | Report Abuse | Link to thisYes, it's a shame that so many animals die due to the ignorance of men, but before you sit and complain about it, perhaps you should consider the part you play. Do you drive a car? Do you use a wood stove? Do you create garbage that is burnt or dumped in a landfill? Do you use cleaning products and beauty aids? Perfume or aftershave? How much plastic do you own? These are the things that create the toxic waste that is not only killing animals, but is killing people. If you live in the industrialized world, you are guilty. And yes, that includes me.
Reply | Report Abuse | Link to thisNow, how much of your lifestyle are you willing to change to save the planet?
Yellow fat disease used to be a well known condition in domestic cats. There are numerous references to it in veterinary literature. The basic cause was a deficiency of vitamin E resulting from a diet that comprised mainly tuna fish. I suggest that before before jumping to an uninformed conclusion that this condition in the Nile crocodiles has a toxic cause, a deficiency of an essential dietary ingredient should be considered. I expect that unaffected crocodiles would have the same foreign chemicals in their tissues as the affected ones.
Reply | Report Abuse | Link to thisnbajzek - priceless.
Reply | Report Abuse | Link to thisRe: Hunting a Croc Killer, SciAm, Oct. 2009: I have some experience with rivers, lakes and reservoirs and have noted from field experience the differences in each. I suspect the key in the epidemiology of the dying crocs may lie in the changes the man-made reservoir has placed on the aquatic ecology of the region. A dam placed on a large river changes everything; physically, chemically and as a consequence the biology also changes, for both aquatic and terrestrial species that formerly depended upon a free flowing stream. The reservoir interupts the natural flow of the region and changes the "seasonal" temperature and chemistry of waters discharging into the tailwater so that the reservoir is not a "natural" lake and the tailwaters are not a "natural" river. Changes in water quality created by the "new" reservoir environment can be quite dramatic. If the reservoir has any depth the standing water will stratify into a temperature gradient from surface to bottom and mixing from the surface will cease, causing also an oxygen gradient where it will completely disappear in the bottom layers and create change in the oxidation/reduction potential (ORP) of this lower region. The lake then essentially becomes an anaerobic septic environment which can cause all manner of problems with solution of products of anaerobic digestion such as methane and will also allow the solution of heavy metals, such as mercury, lead and others. The article also mentions coal mining occurring upstream. Coal is a famous source of all manner of sulfides and toxic metals. Tailings from coal mining entering the reservoir coupled with organic material on the bottom plus the lack of oxygen is a system ripe to generate all manner of toxic substances. Annual fish kills or a lack of fish and/or gill breathing aquatic insects in the tailwaters are a dead giveaway that the lake is generating toxins. Bubbles noted coming up from the bottom of the lake plus rotten egg odors in the discharge are also signs of bad chemistry occurring in the bottom layers of the reservoir. Water entering the resevoir from sidestreams or into the main channel may route through the reservoir as a density current and could conceivable carry toxins through to the tailwater discharge. Since both crocs and fish seem to have the same diagnostic evidence of pansteatitis an epidemiologist would definitely examine the possibility of the newly formed reservoir being the source of toxic chemistry being discharged from the changing ORP occurring within the reservoir.
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