Population survey of Crocodylus niloticus (Nile crocodile) at Lake Sibaya, Republic of South Africa.
Combrink, Alexander Stanislou.
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The Greater St Lucia Wetland Park (GSLWP) World Heritage Site, is one of the most important remaining protected areas for the conservation of Crocodylus niloticus (Nile crocodile) in the Republic of South Africa Although crocodiles are present at low densities in some of the wetlands throughout the GSLWP, at Kosi Bay and Lake Sibaya, the majority is found at Lake St Lucia Concern about the status of the crocodile population at Lake Sibaya prompted a quantitative assessment of the present situation to direct appropriate management action to secure the future viability of this population Due to the complex nature of crocodile surveys, and the paucity of available scientific literature in South Africa, a literature review of global crocodilian survey techniques provided the basis for a survey strategy to determine an index of relative abundance of the crocodile population at Lake Sibaya The population was estimated in 2003 through aerial and spotlight surveys and nest surveys were conducted in 2003 and 2004. The highest count dwing the 2003 aerial surveys was 36 crocodiles, suggesting a decline of 66% during the past 13 years in the population index based on earlier surveys. Sixty five crocodiles were cowlted during the spotlight surveys, 72% more than the highest aerial count (excluding hatchlings), which indicates the importance of using a combined survey approach. A correction factor of 1.72 was calculated for future aerial surveys and the population is estimated at 112 crocodiles, \\-ith a variance of22.49 and standard error of 4.47. Three nests were found during the 2003 nest survey, but none during 2004. Crocodiles rarely produce every year in the wild, and the Lake Sibaya population might display a low reproductive frequency, similar to the nearby Lake St Lucia population Sixty three potential nesting areas were identified and evaluated in terms of their relative suitability for nesting. These sites could play an important role in increasing the population to support a sustainable use progralllffie at Lake Sibaya. Despite legal protection, the population is clearly under threat as a result of direct and secondary pressures. To secure the future viability of this population, I recommend that Ezemvelo KZN Wildlife develop an integrated crocodile management plan through collaboration with The Greater St Lucia Wetland Park Authority and the local communities adjacent to Lake Sibaya, where the conservation and increase of crocodiles will benefit the communities that are dependent on the lake for their daily livelihoods. The likely alternative might be extinction of this important predator from the largest freshwater ecosystem in South Africa's first World Heritage Site.