Abstract:
Repeated annual episodes of Nile crocodile deaths in two isolated areas of the Kruger National Park prompted the investigation of possible organohalogen pollutant involvement.Crocodile eggs were
collected close to one of the mortality sites (Gorge) as well as from a crocodile farm (CF) as reference.
ΣDDT was significantly higher in Gorge (450ng/gwm) than in CF eggs (85ng/gwetmass). Percentage DDT of ΣDDT was significantly higher in CF (14 percent)than in Gorge eggs (5 percent). Mean ΣDDT was almost 70 times higher than mean ΣPCB in Gorge eggs. HCB, β-HCH, mirex, brominated flame retardants (BFRs), and perfluorinated compounds (PFCs) occurred at lower concentrations. We believe
that the BFR and PFCs data represent the first published results for any crocodile egg.Thickening of the outer egg shell layer of Gorge eggs was significantly associated with higher concentrations of ΣDDT.
Concentrations of ΣDDT and other pollutants were in the same range as eggs from elsewhere,where there were no mortalities. Concentrations of ΣDDT in eggs from healthy Australian crocodiles were of the same orders of magnitude as the current study, making it highly unlikely that the concentrations of
pollutants measured in the present study would have caused or substantially contributed towards the
mortalities observed.Concerns about reproduction and behaviour remain.As large predators, crocodilians are at the apex of the freshwater aquatic food web.More research is needed to guide measures to
manage African freshwater systems so that it will also sustainably accommodate these large, long-lived animals.
