Rationale
Listed as Least Concern as the species is relatively widespread within the assessment region, they are abundant, and there are no major threats believed to be resulting in a significant population decline. From available game count data from formally protected areas, private nature reserves and game farms, there are an estimated 22,252 observed Common Warthogs within the assessment region. There is also evidence that the species is expanding its distribution in South Africa, both naturally and through introductions.
Regional population effects: The Common Warthog is widespread across sub-Saharan Africa from West Africa eastwards to Ethiopia and southwards through East Africa and southern Africa to South Africa There may be some dispersal across national boundaries and between neighbouring populations in Botswana, Zimbabwe, Mozambique, South Africa and Swaziland.
Distribution
Within southern Africa, they occur in northeastern Namibia, and extensively in Botswana, Zimbabwe, Mozambique and South Africa. Within the assessment region, the species naturally occurs in the northern and eastern parts of the country from Limpopo Province to the Northern Cape. They occur throughout Mpumalanga, Limpopo and North West provinces and marginally in Northern Cape Province, including Kgalagadi Transfrontier Park, and in the north-eastern areas of KwaZulu-Natal (Skinner & Chimimba 2005). Six isolated introduced subpopulations occur in the southern KwaZulu-Natal (www.kznwildlife.com).
The Common Warthog has often been referred to as P.aethiopicus, but this is the binomial for the Cape Warthog that became extinct before 1870 (Skead 2011). Phacocoerus africanus has been introduced into the former range of P. aethiopicus aethiopicus, including Eastern Cape, Free State and Northern Cape provinces. Boshoff and Kerley (2013) conclude that the Orange River probably represented the northern boundary between Cape and Common Warthog (where all records south probably refer to the Cape Warthog), while the Tugela River was the southerly limit of Common Warthog and records south of 30°S and between 27° and 30°E refer to Cape Warthog. The first extra-limital introductions were made in 1960s and 1970s. An unknown number of Common Warthogs sourced from the Hluhluwe-iMfolozi Park (KwaZulu-Natal), were introduced onto the Golden Gate Highlands National Park (GGHNP), Free State Province, between 1963 and 1968 (Penzhorn 1971). Another group of warthogs (N = 20) also sourced from Hluhluwe-iMfolozi were introduced onto the Andries Vosloo Kudu Nature Reserve (AVKNR) (which now forms part of the Great Fish River Nature Reserve) in the Eastern Cape Province between 1976 and 1977 (Somers 1992a). In 1984, three warthogs were translocated from the AVKNR to the Rolfontein Nature Reserve (RNR) in the Northern Cape Province (unpubl. reserve records). They have also been reintroduced to areas of KwaZulu-Natal and Eastern Cape provinces (Skinner & Chimimba 2005). It is unclear how widely they have been introduced into the Northern and Western Cape provinces.
The species has been reintroduced into game reserves in Swaziland (Monadjem 1998), and likely occurs in low densities along the Caledon River in Lesotho, where their historical occurrence is documented in Boshoff and Kerley (2013), and they have been observed in the vicinity of the Caledon River in the Wepener area since 2013 (E. Schulze pers. obs.).
Warthogs are generally not contained within the borders of a property by standard wire or wire-mesh fencing, and can be considered a âfree-roamingâ species in South Africa. Their home ranges may stretch across a number of fenced properties which includes crop, livestock and game farms, and private or public nature reserves (M. Swanepoel unpubl. data). This has enabled them to disperse and expand their distribution from the initial introduction points in the Eastern Cape and arid Karoo. It is expected that their dispersal and range expansion will continue into areas that meet their habitat requirements. This would include large parts of central and eastern South Africa, with the very arid west coast and the fynbos regions possibly the only exceptions. Since these free-roaming animals are subjected to hunting on private farms and reserves, formally protected areas, where no hunting takes place, might harbour core populations.
Population trend
Trend
The overall number of Common Warthog in southern Africa (Angola, Zambia, Tanzania and southwards) has been estimated at about 250,000 (Cumming 1999). Typical densities range from 1â10 individuals / km² in protected areas (Hunter 1998; Caro 2005; Cumming 2013). Densities in the iMfolozi Game Reserve, KwaZulu-Natal Province, ranged between 26.0 individuals / km2 in 2006 and 22.8 individuals / km2 in 2007 (White 2010). Within Kruger National Park alone, population size was estimated at between 2,000 and 5,000 individuals in 2012, or about 0.25 warthogs / km2 (Ferreira et al. 2013). Overall, using composite data from 147 formally protected areas, private protected areas and game farms within the assessment region, the minimum observed population size for the species in 2013 was 22,252 individuals. In a typical sounder (a group of warthogs), the adults represent roughly 40%, but composition changes seasonally (Somers et al. 1995). Thus, there are estimated to be at least 8,900 mature individuals, which is very likely to be a significant underestimate.
Annual growth rates vary but can be as high as 40â45% under favourable conditions (for example, absence from predators, access to water and burrows, sufficient fodder), such as when introduced to a protected area without predators (Somers 1992a; Somers & Penzhorn 1992), but higher rates have been recorded. For example, in the 15 years since 43 warthog were introduced in Tussen die Riviere Nature Reserve in the Free State Province (protected area, no large predators), the population grew by an average of 62.6% per year, and highest growth rates (between 83% and 106% were recorded 8â11 years after introduction; E. Schulze unpubl. data).
Subpopulations are widespread across South Africa in national and provincial parks, private game reserves and wildlife ranches. Through the expansion of game ranching across South Africa, coupled with potentially high reproductive rates and potentially increasing dispersal events, the national population is likely to be increasing.
Threats
There are currently no major threats to this species. It is widespread and tolerant, and shows remarkable resilience. Populations quickly recover due to their high reproductive rates and large litter sizes (Mason 1990; Somers & Penzhorn 1992). However, the species is susceptible to drought and overhunting or persecution, which may result in localised extinctions (Somers 1997), or localised population fluctuations. Climate change may thus become an emerging threat if it alters surface water distribution, thereby degrading habitat suitability for the species. For example, Ogutu et al. (2011) found warthogs to be influenced by rainfall patterns.
Uses and trade
Common Warthogs have an economic value as a game animal hunted for trophy value and meat provision. International trade is for trophy hunting only â there are no live animals or animal meat traded through concern over the spread of African swine fever. Nationally, however, Common Warthogs are used for local subsistence, commercial meat provision, trophy and recreational hunting, and live animal auctions. Utilisation is unlikely to affect the population. However, the bushmeat trade is increasing rapidly, and in some areas, reserves close to human settlements have been stripped almost clean of wildlife. Warthogs are actively targeted in these hunts as they are easily killed (E. Schulze unpubl. data).
Current research on the animal is primarily directed towards identifying disease risks (Penrith 2009), ecological and biological aspects of introduced populations (Nyafu 2009; Mgqatsa 2010), avenues for management and utilisation of extra-limital populations, and aspects relating to the value of meat (Swanepoel et al. 2014). Additionally, the warthog's potential for parasite transmission is being considered, specifically with regards to African Swine Fever and Bovine Tuberculosis (BTB) (Renwick et al. 2007).
Wildlife ranching has extended the range of this species, and free-roaming subpopulations are expected to expand their distribution in South Africa where there is suitable habitat. They have been actively translocated from their native range to reserves and wildlife ranches across South Africa and high reproductive rates have allowed the species to establish and disperse to wildlife, livestock and crop farms. They are sometimes considered damage-causing animals when responsible for crop raiding or causing damage to fences. Damaged fences may allow previously excluded predators to gain access to vulnerable livestock and game animals. In some agricultural regions they are heavily persecuted by humans for loss reprisal. There are no domesticated Common Warthog subpopulations, but they are sometimes kept as pets.
As part of management efforts, the extensively distributed extra-limital subpopulations should rather be controlled, and perhaps utilised to create rural and commercial meat production systems for local markets. Warthogs have a favourable carcass yield and can be utilised for commercial game meat production (Somers 1992b; Swanepoel et al. 2014). Assigning a monetary value to the species to establish and implement incentives for sustained management and utilisation strategies could further incentivise the shift from livestock agriculture to wildlife ranching.
Conservation
The Common Warthog is present in numerous protected areas, wildlife ranches and agricultural lands across its extensive range within the assessment region. The most important protected areas in their native range include Kruger National Park, Mapungubwe National Park and Marakele National Park in Limpopo Province; Madikwe Game Reserve and Pilanesberg National Park in North West Province; and Hluhluwe-iMfolozi Park and Ndumu Game Reserves in KwaZulu-Natal Province. In their introduced range, key protected areas include the Addo Elephant National Park and Mountain Zebra National Park in the Eastern Cape Province, Golden Gate Highlands National Park and Tussen die Rivere Nature Reserve in the Free State Province, and Mokala National Park in the Northern Cape Province.
Its sustainable use should be continued and enhanced by more formal structures to promote the Common Warthog as an alternative meat source for local communities and commercial markets, which may potentially reduce illegal bushmeat hunting. Conservancy formation will help to create stable and resilient subpopulations of this species that can be used commercially, while increasing management and research efforts should be directed to control extra-limital populations. Landowners should be made aware of alternative interventions to reduce fence and crop damage. For example, the use of swing-gates in game fencing has been shown to reduce the damage caused by warthogs burrowing under fences (Schumann et al. 2006). Similarly, Weise et al. (2014) trialled the use of discarded car tyres as wildlife passageways along the border of a Namibian wildlife ranch to reduce Common Warthog damage, which halved the number of holes needing to be repaired along the fence.
Recommendations for land managers and practitioners: The primary management recommendation is to manage the Common Warthog harvest sustainably. This is a key species to galvanise sustainable wildlife-based economies. More incentives and infrastructure should be put in place to ensure this species is used as a low-carbon, local source of protein to stimulate local economies to encourage game meat consumption and enhance national food security (Swanepoel et al. 2014). To do this, it is necessary to monitor subpopulations and their distribution across seasons, as this would directly influence the degree of harvesting pressure applied to a subpopulation. The best times to monitor subpopulations are during summer and spring, early morning, midday and late afternoon, as these are the times they are most visible (M. Swanepoel, unpubl. data). Secondly, accredited field abattoirs, which can inspect and process carcasses for commercial markets, must be established. Increasing the hunting pressure on cohorts such as piglets and yearlings would possibly simulate natural mortality and population regulation. This has been suggested for feral pig subpopulations, with the added emphasis on removing yearling sows (Gaillard et al. 2000; Gamelon et al. 2012).
Research priorities:
- There is uncertainty regarding the exact distribution of extra-limital subpopulations across central South Africa and the extent of translocations resulting in the spread of P. africanus into the former range of P. aethiopicus where it may be regarded as an invasive species (Skead 2007, 2011). However, this might not affect the current listing. Further research should nevertheless seek to delimit the extent of their current distribution and natural range expansions.
- Similarly, research into the ecological and biological factors contributing to the success of the Common Warthog as an introduced species, and their impact in these areas, should be undertaken. For example, understanding whether small livestock farms are shifting to large livestock or mixed farming practices following the introduction of the Common Warthog in the Northern Cape and Free State provinces. This also includes documenting the internal parasites of extra-limital subpopulations with reference to native subpopulations.
- Determine the risk of Common Warthogs acting as long-term hosts and vectors of potentially harmful livestock and game animal diseases (for example, African Swine Fever).
- Methods of artificially simulating natural mortality patterns in Common Warthog subpopulations as management tool should be developed.
- Further research is needed on practical methods to mitigate the negative ecological and economic impacts caused by Common Warthogs.
Encouraged citizen actions:
- Consume Common Warthog meat and products to stimulate wildlife-based economies.
- Similarly, landowners should manage extra-limital warthog subpopulations commercially for local food consumption.
- Report sightings on virtual museum platforms (for example, iSpot and MammalMAP) to establish the extent of extra-limital distribution within the assessment region.
