Encompassing 12 091 ha in total, the Willem Pretorius Game Reserve is divided into terrestrial (9 443 ha) and aquatic (2 648 ha) habitats. The average annual rainfall is 575 mm and the temperatures range from -0.4 °C minimum to 30.6 °C maximum. The area consists of flat plains (1 360–1 506 m a.s.l.) occasionally interrupted by low koppies and hills that stretch away from the riverbanks.
The reserve falls on the boundary between mixed and sweet grassland. The Allemanskraal Dam and Sand River bisect it into northern and southern terrestrial units, which differ significantly in habitat diversity. The northern section may be described as predominantly broken savanna thornveld on hills and koppies. It consists of densely vegetated hills and ravines interspersed with gently sloping areas of grassland and coppices of acacia trees, providing considerable habitat diversity. By comparison, the habitats in the southern unit are relatively homogenous, consisting primarily of undulating open grassland that supports large populations of plains game species, most of which have been re-introduced.
More than 250 bird species have been recorded in the reserve, of which about 200 are common and/or regularly seen.
Martial Eagle Polemaetus bellicosus, Greater Flamingo Phoenicopterus roseus, Lesser Flamingo Phoeniconaias minor and Caspian Tern Sterna caspia were listed in the original IBA directory (Barnes 1998) as threatened species that did not meet the IBA threshold to qualify as trigger species. As such, they are not listed below as IBA trigger species. Nonetheless, Martial Eagle and Caspian Tern were recorded in SABAP2 data for this reserve and Martial Eagle is resident but no longer breeding inside the reserve.
The arid grasslands surrounding the dam support African Grass Owl Tyto capensis, while large numbers of Black-winged Pratincole Glareola nordmanni occur on the dam shore.
In 1998, the dam regularly supported more than 5 000 waterfowl (Barnes 1998). Although CWAC counts have been shifted to a bit later in the season, the same high numbers, especially for gamebirds (geese), are no longer being observed. This may be an accumulated result of poisoning and wing shooting in the surrounding farmlands where geese feed. The illegal harvesting (nest-raiding) of chicks, and possibly also eggs, from the heronry for use as live bait for catching barbel probably adds to this decline in waterbird numbers.
Globally threatened Maccoa Duck Oxyura maccoa, Martial Eagle, Blue Korhaan Eupodotis caerulescens, Melodius Lark Mirafra cheniana, and European Roller Coracias garrulus; regionally threatened Lanner Falcon Falco biarmicus, Lesser Kestrel Falco naumanni, Yellow-billed Stork Mycteria ibis and Caspian Tern; and biome-restricted Sickle-winged Chat Cercomela sinuata, Kalahari Scrub Robin Erythropygia paena, White-bellied Sunbird Cinnyris talatala and Willow Warbler Phylloscopus trochilus have been recorded in SABAP2. The addition of these species to the IBA trigger list will depend on the availability of additional data and expert opinion to determine whether they meet IBA threshold criteria.
Globally threatened species include Secretarybird Sagittarius serpentarius (at least one pair is resident and breeding) and Black-winged Pratincole (approximately 2 000–3 000). Congregatory birds are Egyptian Goose Alopochen aegyptiaca, Western Cattle Egret Bubulcus ibis, Spur-winged Goose Plectropterus gambensis, South African Shelduck Tadorna cana, Cape Shoveler Anas smithii and African Spoonbill Platalea alba.
The Red Data plant Anacampceros filamentosa is found in the reserve. The rare rock catfish Austroglanis sclateri and striped weasel Poecilogale albinucha have been recorded in the region. The endemic black wildebeest Connochaetes gnou and blesbok Damaliscus dorcas phillipsi and the threatened white rhinoceros Ceratotherium simum and African buffalo Syncerus caffer have been re-introduced. The sungazer lizard Smaug giganteus occurs in some of the grassland areas, while the southern spiny agama Agama hispida and the striped harlequin snake Homoroselaps dorsalis may occur in small numbers in suitable habitat.
Willem Pretorius Game Reserve is surrounded by commercial farmland, which is used mainly for sheep and cattle grazing. Here, as is the case for all nature reserves in the Free State, one of the biggest threats to its biodiversity is the ‘island effect’, which occurs when severe land degradation and transformation outside the reserve leaves little natural veld remaining and few corridors between habitats. The size of this reserve is not large enough for it to meet conservation targets for these vegetation types.
The water flowing into the Allemanskraal Dam has a high silt load and is polluted, to a degree, by various agrochemicals. Poison (usually Temmick) is thrown out by farmers in surrounding areas, such as newly planted wheat fields, for Egyptian Goose, Spur-winged Goose, Helmeted Guineafowl Numida meleagris and other ‘pest’ species. Poisoned birds that return and die inside the reserve may then cause secondary poisoning and mortality for predators and scavengers that eat the carcasses. The secondary poisoning of African Fish Eagle Haliaeetus vocifer has been reported. Since the poisoning is hard to trace and prove, it is also hard to prosecute perpetrators.
The large heronry on the island depends on both indigenous and invasive trees and bushes. However, if the invasive red river gums Eucalyptus camaldulensis, in which the birds breed, are cleared and the birds stay on and make use of only the indigenous trees and bushes, these may be killed by the ‘avian excreta’. The heronry is also under threat from nest-raiding, as the chicks of heron, egret, cormorant and other species are stolen for use as live bait to catch barbel.
Power-boating and jet-skiing are allowed on the dam and result in noise disturbance, especially near the island and the main shoreline.
The IBA is fully protected as part of the Willem Pretorius Game Reserve, which was established and proclaimed in 1970. A five-year Integrated Management Plan for the reserve was developed by FS DETEA in 2011. Implementation of the plan is considered to be effective and financial resources are generally adequate at present. However, the human resource structure and capacity are insufficient to meet management requirements.
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WPGRMP. 2011. Integrated Management Plan Willem Pretorius Game Reserve. Unpublished report. The Department of Economic Development, Tourism and Environmental Affairs Free State Province.