Hooo-Hooo Hooo-Hooo Vol. 13 Issue 01 - Page 5

Artificial dams in the KNP are mostly shallow stagnant water systems subject to considerable evaporation and sedimentation. Hippo that urinate and defecate in such dams cause a build-up of phosphate-rich sediment. High animal densities that develop around water points may also increase run-off of faecal material in to the dams. Warm water temperatures, high hippo densities and stirring up of the sediments by the hippo result in progressive eutrophication and cyanobacterial proliferation. Mortalities occurred when the wind blew algal rafts to areas of preferred drinking on the dams. That no elephant, buffalo and hippo deaths were seen may be because these species tend to drink at any part of the dam and wade into the water to drink (therefore ingest water away from the algal raft). Small dams are important features of the landscape for both tourists and animals in the KNP. The natural migration of animals to wetter areas in dry seasons and years is no longer possible. Preventing further mortalities, particularly of threatened or endangered species was a priority, but no easy solutions were available in this complex habitat. Possible control measures included reducing faecal loading of dams, however lethal hippo removal was not possible and burning of the veld around (or fencing) a dam would impact large numbers of animals. Hippo culling or adding spillways to the dams would not remove the dense layers of hippo dung already present on dam floors. Removing sediment in dams by flushing them out in the wet season (in wet years), emptying and dredging dams, the use of copper sulphate or phosphate binders were all considered impractical, ecologically disruptive or unlikely to be effective. Floating booms would likely have been disrupted by animals and/or rendered useless by changing wind direction. In the end, breaching the dams prevented further major mortality events by causing the hippo to move away. eutrophication and harmful algal blooms. Such blooms continue to occur sporadically in the KNP (as well as other parks and game farms) so monitoring by wildlife managers and veterinarians is needed to detect mortality clusters around affected dams, particularly in early winter, that could be due to cyanobacterial intoxication. Borehole-fed concrete troughs are less likely to have algal blooms. Early testing of water for the algae and their toxins is needed to confirm the diagnosis. Probably the most visible example of unintended consequences, is what happens every time humans try and change the natural ecology of a place – MJ Wheatley (writer and management consultant) Roy G Bengis, Danny Govender, Emily Lane, Jan G Myburgh, Paul J Oberholster, Dewald F Keet, Peter E. Buss and Leon Prozesky 2016 Eco-epidemiological and pathological features of mortal- ity events related to cyanobacterial bio-intoxication in the Kruger National Park. Journal of the South African Veterinary Associa- tion 87(1), a1391. http://dx.doi.org/10.4102/jsava.v87i1.1391 While the recent drought has significantly reduced hippo numbers, future solutions could include replacing dams with artificial wetlands or adding vegetated islands to dams. Increasing the aquatic biodiversity would make dams less prone to 2019 ISSUE 01 5