Common Warthog (Phacochoerus africanus)
Fig 1. A male Southern Warthog (Phacochoerus africanus sundevalli) from South Africa.
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Taxonomy
The common warthog (Phacochoerus africanus) is one of two extant species of the genus Phacochoerus and belongs to the pig family Suidae (9), specifically the sub-saharan African suids (14, 15). It was originally considered the only remaining warthog, but morphological and genetic analyses suggest the survival of another species, the desert warthog (Phacocheorus aethiopicus) in a population previously assigned to the common warthog (9). The split between these two species is deep, dating to about 4.5 mya, during the Pliocene epoch (9). The closest relative of the two warthog species is the giant forest hog (Hylochoerus meinertzhageni) Several fossil taxa are considered synonymous to P. africanus including P. mauritanicus, P. barbarus, P. congolensis and P. helmei (7). The species is further divided into four subspecies: The Nolan warthog (P. a. africanus), the Eritrean warthog (P. a. aeliani), the Central African warthog (P. a. massicus) and Southern warthog (P. a. sundevalli) (12, 13) and genetic evidence supports the legitimacy of all these subspecies, except the rare Eritrean warthog which has not yet been studied (12).
Distribution
The common warthog is, as the name indicates, common. Its range covers the majority of sub-Saharan Africa and it is classified as Least Concern by the IUCN Redlist (5). The Nolan warthog has a range ranging from the Atlantic coast in Mauritania to the Gulf of Aden in Northern Somalia, with its southernmost occurrence on the Northern edge of the Congo Basin. The central African warthog is found in Eastern Africa, from Northern Mozambique and Zambia to Kenya and the Southern warthog stretches from Angola to South Africa and Mozambique. The Eritrean warthog is restricted to a small range in Northern Ethiopia and Eritrea (12). Three major areas of Sub-saharan Africa lacks common warthogs. Firstly, the Congo Basin may not contain suitable habitats for warthogs, though fossil evidence suggests this has not always been so (7). Additionally, the Cape and much of the horn of Africa, which are the native ranges of the desert warthogs, a species that appears to dominate the common warthog in arid zones (4). Since the extinction of the Cape warthog (Phacochoerus aethiopicus aethiopicus), the common warthog has managed to disperse into the Eastern Cape (8). Fossil evidence suggests that they once occurred in North Africa as well (7).
Fig 2. IUCN Ranges of the desert warthog (Phacochoerus aethiopicus) in blue and the common warthog (Phacochoerus africanus) in red, with a purple overlap zone. As seen there are small areas of sympatry but the general range division may indicate a high degree of competition (4). Fossil sites are indicated by ammonite markers, but in most cases the two species of Warthog are not distinguished between so sites are only specific to the genus level.
Ecology
The common warthog is a medium-large suid, averaging 83kg (6). Warthogs usually form groups called sounders which vary in size from only a pair to 9-10 animals, and in exceptional cases over a dozen (3). The mean group sizes vary, one study suggests 5-6 individuals during the wet season with smaller groups during dry periods(3). The structure of each group differs greatly and may contain juveniles, sub-adult, males and/or females, though groups formed around an adult female (which doesn’t include adult males) or strictly male bachelor groups are most prevalent. Solitary males are also quite a common occurrence (3).
The diet of the common warthog is variable but primarily consists of grasses, though the species exhibits omnivory. Primarily the feeding methods employed by the common warthog are grazing or rooting, the importance of these two strategies fluctuates between regions (3) and probably reflects local availability. The common warthog preferably feeds on the growing grass tips, in a process called ‘plucking’ in which its incisors are used to pull smaller strands of grass (3). Elsewise, the warthogs can competently consume larger grass species by jerking their heads whilst holding the vegetation with their teeth, this strategy is also used to consume inflorescence (3). C4 Grass species which are rich in nutrients, especially Nitrogen are preferred (2, 11). Rooting on the other hand is a function largely performed by the snout, which is used to dig shallow holes to access roots and bulbs (3). Meat consumption has been observed but is rare, this is both in the form of carrion and live smaller prey such as insects, snakes, rodents, and even juvenile gazelles (3, 10).
Due to the preference for rich grazing, common warthogs are most plentiful in savannah habitats with rich soils, (3) but are also capable of inhabiting shrubland, wooded grasslands, and even montane and semi-desert habitats (7). The savannah ecosystems throughout Africa are home to a rich ensemble of other herbivorous megafauna. a dietary analysis suggests that the common warthog is most similar to the Cape buffalo (Syncercus caffer) and Waterbuck (Kobus ellipsiprymnus) in dietary niche, at least in Kruger national park. Other animals with similar diets include wildebeest (Connochaetes spp.), hippopotamus (Hippopotamus amphibius), Zebras (Equus hippotigris spp.), and various species of antelope (2). The ecosystem is also home to a plethora of predators. Predation is the chief cause of mortality in the common warthog, at least in Zimbabwe where a study was conducted (3). In this area, the lion (Panthera leo) accounts for the bulk of kills, though leopards (Panthera pardus) and spotted hyaena (Crocuta crocuta) also were significant predators (3), elsewhere African wild dogs (Lycaon pictus) and occasionally cheetah (Acinonyx jubatus) have also been observed to prey on warthogs (3). Eagles commonly predate on piglets (3). The iconic tusks of the warthog are enlarged canines and act as a defensive weapon against predators and are used to deter attackers, as well as in intraspecific competition usually in establishing mating rights (1). The upper canines can reach up to half a meter in length (1).
Citations
1. Chen, P.Y., Lin, A.Y.M., Lin, Y.S., Meyers, M.A., McKittrick, J. (2010). Structure, Function and Mechanical Properties of Selected Biological Materials, 安泰醫護雜誌 16 (3), 135-166.
2. Codron, D., Codron, J., Lee-Thorp, J.A., Sponheimer, M., de Ruiter, D.J., Sealy, J., Grant, R., Fourie, N.. (2007). Diets of savanna ungulates from stable carbon isotope composition of faeces, Journal of Zoology 273, 21-29.
3. Cumming, D.H.M. 1975, A Field Study of the Ecology and Behaviour of Warthog, Department of National Parks & Wild Life Management, Salisbury, Rhodesia.
4. d’Huart, J-P., Grubb, P.. (2001). Distribution of the common warthog (Phacochoerus africanus and the desert warthog (Phacochoerus aethiopicus) in the Horn of Africa. African journal of Ecology 39, 156-169.
5. de Jong, Y.A., Cumming, D., d'Huart, J. & Butynski, T.. (2016). Phacochoerus africanus (errata version published in 2017). The IUCN Red List of Threatened Species 2016.
6. Faurby, S., Pedersen, R. Ø., Davis, M., Schowanek, S. D., Jarvie, S., Antonelli, A., & Svenning, J.C. (2020). PHYLACINE 1.2.1: An update to the Phylogenetic Atlas of Mammal Macroecology.
7. Grubb, P., d’Huart, J-P.. (2010). Rediscovery of the Cape Warthog Phacochoerus aethiopicus: A review. Journal of East African Natural History 99(2), 77-102.
8. Nyafu, K.. (2009). Warthog as an introduced species in the Eastern Cape. Masters Thesis, Nelson Mandela Metropolitain University.
9. Randi, E., D’Huart, J-P., Lucchini, V., Aman, R.. (2002). Evidence of two genetically deeply divergent species of warthog, Phacocheorus africanus and P. aethiopicus (Artiodactyla: Suiformes) in East Africa. Mammalian Biology 76, 91-96.
10. Roberts, B.A.. (2012). An attack by a warthog Phacochoerus africanus on a newborn Thomson's gazelle Gazella thomsonii. African journal of ecology 50(4), 507-508.
11. Treydte, A.C., Bernasconi, S.M., Kreuzer, M., Edwards, P.J.. (2006). Diet of the Common Warthog (Phacochoerus africanus) on Former Cattle Grounds in a Tanzanian Savanna. Journal of Mammalogy 87 (5), 889-898.
12. Muwanika, V. B., Nyakaana, S., Siegismund, H. R., Arctander, P.. (2003). Phylogeography and population structure of the common warthog (Phacochoerus africanus) inferred from variation in mitochondrial DNA sequences and microsatellite loci. Heredity 91, 361-372.
13. Girma, Z.. (2018). Habitat preferences of the Bohor Reedbuck (Redunca redunca) and Common Warthog (Phacochoerus africanus) in Arsi Mountains National Park, South-eastern Ethiopia. International Journal of Ecology and Environmental Sciences 44 (3), 227-237.
14. Frantz, L., Meijaard, E., Gongora, J., Haile, J., Groenen, M.A.M., Larson, G.. (2016). The Evolution of Suidae, Annual review of animal biosciences 4(1), 61-85.
15. Gongora, J., Cuddahee, R.E., Nascimento, F.F.d., Palgrave, C.J., Lowden, S., Ho, S.Y.W., Simond, D., Damayanti, C.S., White, D.J., Tay, W.T., Randi, E., Klingel, H., Rodrigues-Zarate, C.J., Allen, K., Moran, C., Larson, G. (2011). Rethinking the evolution of extant sub-Saharan African suids (Suidae, Artiodactyla). Zoologica scripta, 40, (4). 327-335.