Skinner (2013) estimated the total population size for Springbok in southern Africa at c. 2,000,000â2,500,000 animals, with approximately 60% of the population occurring on privately-owned land (East 1999). For provinces where fairly comprehensive estimates of the private Springbok population are available (Free State and North West), we estimate a higher proportion of the population on private land: 76â89%. Specifically for South Africa, Skinner (2013) estimated 75,000 in the Free State, 75,000 in the former Transvaal provinces, 1,000,000 in the Karoo and about 100,000 in the Cape provinces outside of the Karoo. However, these are most likely overestimates based on current (2013â15) observed game count data in South Africa. For example, we estimate only 42,731 animals in Free State and 109,209â110,778 in total across the country. As the private sector data is incomplete in most provinces, this figure is likely to be an underestimate. Given that the proportion of mature individuals in a herd is typically 70â73% (C. Anderson unpubl. data), we infer a total mature population of at least 76,446â77,545 animals. The largest subpopulation occurs on the South African side of Kgalagadi Transfrontier Park, where Springbok numbers were 1,935 (wet season count) and 2,217 (dry season count) in 2012 (Ferreira et al. 2016). While the number of cross-border Springbok dropped dramatically in the late 1980s, they have stabilised since with no dramatic declines being recorded in recent years. It is unclear why there was a dramatic decline. It is possible that human-induced factors such as fences, roads and cattle post development were responsible for this decline (Mills and Mills 2013).
Chelsmford Nature Reserve in KwaZulu-Natal falls within the natural distribution range and thus is included in the population estimate. While no formally protected subpopulations exist in Limpopo, some private subpopulations do. It is unclear whether these are extralimital as property coordinates are not available. They are currently included in the population estimate. Similarly, for Mpumalanga, while one private nature reserve is known to fall within the natural range, the other is not (due to missing coordinates) but is included in Table 2 for now. For formally protected areas, while we include Nooitgedachtdam Dam Nature Reserve (as it is on the border of the natural range) we exclude Songimvelo Nature Reserve as it falls significantly outside the natural range. In both Limpopo and Mpumalanga provinces (as well as the Cape provinces), the numbers of private subpopulations are likely to be significantly more extensive than the sample displayed in Table 2 but no comprehensive data are available at present. Further collation of such data is important. However, not all private subpopulations will count towards the wild population if they are intensively and/or captive managed. Further research is required to determine which private subpopulations are eligible.
Generation length has been estimated as seven years (Pacifici et al. 2013), making the three generation window 21 years (1994â2015). Based on 30 formally protected areas from across the natural range of Springbok with adequate long-term data available, we estimate a net 8â27% national increase in population size over three generations (14,927 to 16,542 animals). It is well-known that Springbok experience population fluctuations. Thus, further long-term datasets should be made available to estimate population trend more accurately. There are also worrying examples of local subpopulation declines across its range, the largest of which has been seen in Karoo National Park, having declined from 2,163 to 794 animals between 1994 and 2015 (Gaylard et al. 2016). Reasons for the decline are largely unknown but may include Allee effects following a crash after intense culling in 2000 (of c. 50% of the subpopulation) and subsequent park expansion. Subpopulations also show mixed success in the North West Province. For example, at Bloemhof Dam Nature Reserve, numbers have increased from 479 in 1999 to 1,202 in 2015, but have declined in Molopo Nature Reserve recently by 14% between 2014 and 2015, contrary to expected as the veld was dominated by short grass especially around the pans (Nel 2015). They have declined especially in Mafikeng Nature Reserve from 738 in 1999 to 108 in 2015.
Recent subpopulation declines (since 2009) have also been recorded in parts of the Free State (E. Schulze unpubl. data), North West (Nel 2015) (especially on communal lands, Buijs 2010) and Northern Cape (M. Smit unpubl. data) provinces, possibly due to predation, habitat changes and disease. For example, the decline in numbers in the Kimberley area from 2009 until 2013 (5,573 to 4,855 animals), excluding the sharp spike in 2010 (6,826 animals), can be directly attributed to the higher than normal rainfall experienced during this period (C. Anderson unpubl. data), where most of the pans, which are prime habitat and feeding spots for Springbok, were inundated with water and resulted in taller grass stands. It is well known that a wet substrate and tall grass stands are not optimal habitat for Springbok (Skinner and Chimimba 2005). The occurrence of âhoof-rotâ (vrotpootjie) was also reported on certain properties (C. Anderson unpubl. data). A rapid turnaround of this situation took place from 2014 into 2015, when the area experienced a severe dry spell, and a rapid improvement in the rate of recruitment, as well as more synchronised lambing, was experienced. Springbok in the Northern Cape normally show distinct lambing peaks in autumn (AprilâMay) and spring (September). This was completely disrupted during the excessively wet period, which also increased the predator (jackal) impact on the herds. Another phenomenon experienced during periods of stress were the birth of more males than females (Krüger et al. 2005), as well as physical signs (limited) of foetal resorption (tiny foetuses) (examination of foetuses by C. Anderson).
