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LOCATION OF THE OLIFANTS RIVER
The Olifants River has its origin near the town of Breyten on the Highveld Grasslands of thMpumalanga province in South Africa (Figure 3). The upper reaches of the river flows through the industrial and mining area near the towns of Witbank and Middelburg in Mpumalanga before it cuts through the mountains to the Loskop Dam. From here, the Olifants River meanders through the Springbok flats; passes the Strydpoort Mountains and carries on through the Drakensberg Mountains to descend over the escarpment. Finally, the Olifants River flows through the Lowveld and the Kruger National Park. Crossing the international border, the river flows into the Massingire Dam in Moçambique and eventually on to the Indian Ocean. The Olifants River catchment covers approximately 54 570 km2 and is subdivided in nine secondary catchments (Water Research Commission, 2001). The area covered by the catchment is equal to 4.3% of the total surface area of the whole of South Africa and 18.9% of the former Transvaal province (Kleynhans, 1992). A total run-off of approximately 1 861 million m3 is recorded annually in the Olifants River catchment (Kleynhans, 1992). This run-off is equal to 4.1% of the annual run-off recorded for the entire South Africa (O’Keeffe, 1986). According to the Department of Water Affairs and Forestry (2008), the total length of the Olifants River from its origin to the mouth near the town of Xai-Xai on the Indian Ocean coast of Moçambique is approximately 954.9 km.
Estimated number of crocodiles per area
Survey results clearly show that Nile crocodiles prefer and utilise certain areas of the Olifants River more than other areas. The Kruger National Park and specifically the area of the Olifants River Gorge was one of the areas with the highest number of crocodiles present, to the extent that 28.63% (n = 212) of all crocodiles observed where located in this area. The even higher percentage of 41.59% (n = 308) of all crocodiles observed, occurred in the rest of the Olifants River in the Kruger National Park. Therefore more than seventy percent (70.22%) of all crocodiles in the Olifants River occurs within the boundaries of the Kruger National Park (this constitutes 16.45% of the total Olifants River length). The ecological status of the Olifants River in this region is given as Class C which means that it is considered to be only moderately modified (Nel et al., 2004). The ecological status of the river was determined by taking factors such as flow, inundation, water quality, stream bed condition, introduced in-stream biota and the riparian or stream bank condition into account (Nel et al., 2004). This means that the river and its surroundings are probably still providing good basking and nesting sites, probably have an abundant food source and provide enough deep pools and flowing water for crocodiles to shelter and survive in this area. The other 29.78% of the population occur over 83.55% of available river. The ecological status of the Olifants River in this area is given as Class D which means that the river is considered to be largely modified and transformed from its original state (Nel et al., 2004). It is therefore, conceivable that the river no longer provide good basking and nesting sites and that the food source is probably not plentiful making this area less suitable for crocodiles to survive. In contrast with this, 15.73% of the total Nile crocodile population in the Olifants River occur in the Flag Boshielo Dam. The ecological status of this area is given as Class E/F which means that the river is seriously to critically modified in that specific area (Nel et al., 2004). However the dam did provide excellent basking and nesting sites and a plentiful food source before the wall was raised causing the high percentage of crocodiles present in the area. However this situation has now changed with a reported drop of 27.41% in crocodile numbers since 2005 to a mean population of only 117 animals.
Chapter 1 The importance of crocodilians in the ecosystem
References
Chapter 2 Detailed overview of the Olifants River Basin
Location of the Olifants River
Topography of the Olifants River Basin
Geology of the Olifants River Basin
Landforms of the Olifants River Basin
Biomes and bioregions of the Olifants River Basin
Vegetation types of the Olifants River Basin
Present ecological state of the Olifants River
Land-use of the Olifants River Basin
Climate of the Olifants River Basin
References
Chapter 3 The conservation status and distribution of Nile crocodiles in the Olifants River
Introduction
Location of the survey area
Methods
Results
Discussion
Conclusion
Recommendations
References
Chapter 4 The current Nile crocodile population in the Loskop Dam, a case of ‚crocs in crisis‛
Introduction
Methods
Results
Discussion
Conclusion
References
Chapter 5 Blood biochemistry of Nile crocodiles in the Olifants River
Introduction
Methods
Results
Discussion
Conclusion
References
Chapter 6 Conservation and management plan for the wild Nile crocodile population in the Olifants River, Mpumalanga province
Introduction
Species concerned
Agency responsible
Conservation status and legislative framework
Biology of the Nile crocodile
Threats to the Nile crocodile population of the Olifants River
Goals and objectives
Management
References
Chapter 7 The Nile crocodile population of the Olifants River, is there a future?
References
Summary
Opsomming
