Project

Distribution of the Common warthog (Phacochoerus africanus) and the Desert warthog (P. aethiopicus) in the Horn of Africa and N Kenya.

Goal: The rediscovery of Ph. aethiopicus in N Kenya, Ethiopia and Somalia prompted a detailed investigation on the respective distribution of the two species of warthog, with a focus on their status, habitat, diet and behaviour. Areas of sympatry help determine their distinct ecological niche and possible interspecific interactions. Joint research project with Drs Y. de Jong and T. Butynski.

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Yvonne A. de Jong
added 2 research items
African wild pigs have a contentious evolutionary and biogeographic history. Until recently, desert warthog (Phacochoerus aethiopicus) and common warthog (P. africanus) were considered a single species. Molecular evidence surprisingly suggested they diverged at least 4.4 million years ago, and possibly outside of Africa. We sequenced the first whole-genomes of four desert warthogs and 35 common warthogs from throughout their range. We show that these two species diverged much later than previously estimated, 400,000–1,700,000 years ago depending on assumptions of gene flow. This brings it into agreement with the paleontological record. We found that the common warthog originated in western Africa and subsequently colonized eastern and southern Africa. During this range expansion, the common warthog interbred with the desert warthog, presumably in eastern Africa, underlining this region’s importance in African biogeography. We found that immune system–related genes may have adaptively introgressed into common warthogs, indicating that resistance to novel diseases was one of the most potent drivers of evolution as common warthogs expanded their range. Hence, we solve some of the key controversies surrounding warthog evolution and reveal a complex evolutionary history involving range expansion, introgression, and adaptation to new diseases.
Two species of warthog are currently widely recognised, the poorly known desert warthog Phacochoerus aethiopicus and the widely distributed common warthog Phacochoerus africanus. Spatial data for both species were collected during field surveys and from the literature, museums, colleagues, naturalists, local experts, and online resources to assess their biogeography in the Horn of Africa (HoA). Their distributions were overlaid with ArcGIS datasets for altitude, rainfall, temperature, and ecoregions. Phacochoerus aethiopicus appears to be restricted to Ethiopia, Kenya, and Somalia, with no records west of the Eastern Rift Valley (ERV). The estimated current geographic distribution of P. aethiopicus is 1,109,000 km2. Phacochoerus africanus occurs in all five countries of the HoA and has an estimated current geographic distribution in the HoA of 1,213,000 km2. Phacochoerus africanus appears to be the more adaptable species although P. aethiopicus is able to live where mean annual rainfall is more variable. Although both species are allopatric over vast regions, they are sympatric in central east Ethiopia, north Somalia, central Kenya, north coast of Kenya, and southeast Kenya. Both suids remain locally common, their populations are, however, in decline due to the negative impacts on the environment by the rapidly growing human populations in all five countries.
Yvonne A. de Jong
added a research item
Desert warthog Phacochoerus aethiopicus delamerei and common warthog Phacochoerus africanus are widespread and locally common in the Horn of Africa and Kenya, east of the Eastern Rift Valley. It is of particular interest that these two taxa, the only two extant species in the genus Phacochoerus, occur in sympatry in some regions. Within Kenya, sympatry is known for the northern coast, Tsavo East National Park, Tsavo West National Park, and Meru National Park. This article presents information on a fifth region of sympatry, Laikipia County, central Kenya. Individuals that we judged to be atypical for either desert warthog or common warthog were encountered in Laikipia. New information on the distribution, abundance, population structure, ecology, and behaviour of desert warthog in Laikipia is presented. Laikipia offers considerable opportunity for comparative research on the morphology, molecular biology, ecology, and behaviour of desert warthog and common warthog.
Yvonne A. de Jong
added a research item
Yvonne A. de Jong
added a research item
New desert warthog (Phacochoerus aethiopicus) records for Laikipia County, Kenya
Jean Pierre d'Huart
added 5 research items
Two species of warthogs (Phacochoerus), differing by the number of functional incisors, were described in the Holocene fossil record: the common warthog (P. africanus), widespread in sub-Sahar-an Africa, and the Cape, or desert warthog (P. aethiopicus), which was considered extinct since 1896, but was recently rediscovered in East Africa by morphological analyses. Mitochondrial and single-copy nuclear DNA sequences show that common and desert warthogs belong to two deeply divergent monophyletic lineages, that might have originated in the last part of the Pliocene. The finding of two genetically divergent extant species of warthogs highlights the importance of molecular methods applied to the knowledge and conservation of biodiversity in Africa, to uncover the tempo and mode of its species evolution.
Warthogs without incisors were described from the Cape of Good Hope as Phacochoerus aethiopicus and warthogs possessing incisors were first found in Senegal and later named Phacochoerus africanus. During the second half of the 18th century and the whole of the 19th century, the majority of workers recognised these two taxa as distinct. Twentieth century palaeontologists working in Africa also recognised the two species of warthogs in the Pleistocene and Holocene fossil records and were aware of the differences between the two Recent species. But in the same period, most zoologists considered all warthogs to belong to a single polytypic species. Re-examination of the literature and inspection of recent material confirm distinctive differences corresponding with geographic distribution of two species of warthogs: the widespread common warthog Phacochoerus africanus and the Cape warthog P. aethiopicus. Whereas the Cape warthog, P. aethiopicus aethiopicus, became extinct in South Africa in the 1870s, it survives in Kenya, Ethiopia and Somalia as a geographically isolated subspecies, P. aethiopicus delamerei. This discontinuous distribution has been noted in the literature, as are the criteria which distinguish P. aethiopicus from P. africanus.
Yvonne A. de Jong
added 2 research items
Names Genus: warthogs Phacochoerus F. Cuvier, 1826 Species: desert warthog Phacochoerus aethiopicus (Pallas, 1766) Subspecies: Cape warthog Phacochoerus aethiopicus aethiopicus (Pallas, 1766) Subspecies: Somali warthog or Lord Delamere’s warthog Phacochoerus aethiopicus delamerei Lönnberg, 1909 Synonyms: angalla, delamerei, edentatus, pallasii, typicus French: Phacochère du désert; German: Wüstenwarzenschwein; Spanish: Facóquero del desierto; Italian: Facocero del deserto Names in other languages: Kiswahili: Ngiri; Afrikaans: Kaapse vlakvark; Dutch: Woestijnknobbelzwijn Other common names: vlakvark, African lens-pig, naked swine Taxonomy First described as Aper aethiopicus Pallas, 1766 based on a live warthog from Cape Colony (area between Kaffraria and Great Namaqualand), South Africa, sent by the Governor of the Cape of Good Hope, Ryk Tulbagh, to the menagerie of the Prince of Orange in The Hague, the Netherlands (Rookmaaker 1989; Skead 2011). Pallas noted the absence of incisors in this individual. The species was acknowledged by Cuvier (1810, 1816) who, in 1826, applied the genus name ‘Phacochoerus’ (‘a pig bearing a wart’; Morrison-Scott 1953; Grubb & d’Huart 2010). In 1788, Gmelin described a second species of warthog, the common warthog Sus africanus (now Phacochoerus africanus), from Cap-Vert, Senegal, which possessed well-developed, functional upper and lower incisors (see Chapter 9 of this book). Although various authors, including Cuvier (1816), Lönnberg (1909), Roosevelt and Heller (1915), and Heller (1914), accepted the two species of warthog, Lydekker (1908, 1911, 1915) considered both warthog taxa as one species, the common warthog, and erroneously referred to the species as ‘P. aethiopicus’. Lydekker’s taxonomic arrangement was followed by most authors with the result that, during the twentieth century, it was generally accepted by zoologists that there was but one species of warthog. Some palaeontologists, however, continued to recognize two species (Ewer 1957; Cooke & Wilkinson 1978; Grubb & d’Huart 2010, 2013; d’Huart et al. 2013; Grubb 2013). Phacochoerus a. delamerei was first described by Lönnberg (1909) from a Somali specimen. Although Lönnberg gave the name ‘Phacochoerus delamerei’ to this specimen, he recognized its resemblance to the Cape warthog of South Africa. Phacochoerus delamerei was accepted and additional specimens were obtained from Kenya. Lydekker (1908, 1911, 1915), however, (wrongly) considered delamerei to be a subspecies of the common warthog.
Names Genus: Warthogs Phacochoerus F. Cuvier, 1826 Species: Common warthog Phacochoerus africanus (Gmelin, 1788) Subspecies: Northern warthog Phacochoerus africanus africanus (Gmelin, 1788) Subspecies: Eritrean warthog Phacochoerus africanus aeliani (Cretzschmar, 1826) Subspecies: Central African warthog Phacochoerus africanus massaicus Lönnberg, 1909 Subspecies: Southern warthog Phacochoerus africanus sundevallii Lönnberg, 1909 French: Phacochère commun; German: Warzenschwein; Spanish: Facóquero comón; Italian: Facocero Names in other languages: Dutch: Wrattenzwijn, Knobbelzwijn; Kiswahili: Ngiri; Afrikaans: Vlakvark; Portuguese: Facochero Other common names: African lens-pig, naked swine, kolobe Taxonomy The taxonomy of Phacochoerus africanus is very uncertain and in need of revision (Lönnberg 1909; Hollister 1924; Bigourdan 1948; Haltenorth 1963; Ansell 1972; Grubb 1993, 2005; Groves & Grubb 2011). Current taxonomy is based almost entirely on skull size and proportions, of which much geographic variation exists. It may be a monotypic species. Geographic variation appears clinal. Until further study, four subspecies are provisionally recognized (Grubb 1993, 2005): africanus, aeliani, massaicus, and sundevallii. This taxonomy was adopted by Vercammen and Mason (1993), Skinner and Chimimba (2005), Meijaard et al. (2011), and Cumming (2013). Muwanika et al. (2003) found three well-defined mitochondrial haplotype clades within P. africanus: western, eastern, and southern Africa. That more clades might be present is suggested as this study did not sample within the range of P. a. aeliani, and very large areas in the north-west, north, north-east, and south-east of the range of P. africanus were not sampled. Early taxonomy was much confused with that of desert warthog Phacochoerus aethiopicus. See Grubb (1993), Grubb and d’Huart (2010), d’Huart et al. (2013), and Chapter 10 of this book for historic overviews of the taxonomy of Phacochoerus. Synonyms: aeliani, aelianii, barbatus, barkeri, bufo, centralis, fossor, haroia, incisivus, massaicus, sclateri, shortridgei, sundevallii. Subspecies and Distribution Historic Geographic Distribution Phacochoerus africanus is endemic to the savannas and open woodlands of sub-Saharan Africa (outside forest) from the Atlantic Ocean in West Africa (Mauritania, Senegal, The Gambia, Guinea-Bissau, Guinea) eastwards to the Red Sea (Eritrea, Djibouti, Somalia), and southwards through eastern Africa to the Indian Ocean.
Yvonne A. de Jong
added a research item
There are only two species of warthog, and both occur in Kenya; the common warthog Phacochoerus afri-canus and the desert warthog Phacochoerus aethiopicus. Little is known about the natural history of the desert warthog—in-deed, the desert warthog might well be Africa's least-known, non-forest, large mammal. The morphological differences between the two species of warthog are described by Grubb (1993) and by d'Huart & Grubb (2005). The most diagnostic and noticeable characteristics for both species are summarized in Box 1. d'Huart & Grubb (2001) compiled a map depicting the geographical range of both the common warthog and the desert warthog in the Horn of Africa (Er-itrea, Djibouti, Somalia, Ethiopia, Uganda and Kenya). Their findings were summarized in 2002 by Boy in Swara 25—1: 20-21. The authors found the desert warthog to occur from Puntland (northern Somalia) southwestward through Somalia and southeastern Ethio-pia to central and eastern Kenya. The only sites shown on the map for Kenya were Moyale, El Wak, Merelle ('midway between Arch-er's Post and Mt Marsabit'), and Mkokoni (in the Kiunga Marine Reserve). The southernmost How to most readily differentiate the desert warthog from the common warthog in the field (d'Huart & Grubb 2005). See Figures 1 and 2.
Yvonne A. de Jong
added a research item
Species account: Common warthog (Phacochoerus africanus)
Yvonne A. de Jong
added a research item
Species account: Desert warthog (Phacochoerus aethiopicus)
Yvonne A. de Jong
added 2 research items
Both species of warthog, the common warthog Phacochoerus africanus and the desert warthog Phacochoerus aethiopicus, occur in Kenya. The desert warthog may be Africa's least known non-forest large mammal as its distribution is poorly understood and it has never been the focus of an ecological or behavioural study. None of the earlier books and field guides on the mammals of eastern Africa mention the desert warthog (e.g., Dorst & Dandelot 1969, Haltenorth & Diller 1977, Kingdon 1979), and no game laws recognise this taxon (I. Parker, pers. comm.). Kingdon (1997) is the first major work to recognize the desert warthog as a full species and to bring this species to the attention of a large audience. The preliminary distribution map for the desert warthog compiled by d'Huart & Grubb (2001) presents only four localities for Kenya. They show the southern-most locality as Mkokoni, 60 km northeast of Lamu Island (north coast of Kenya). d'Huart & Grubb found no evidence for desert warthog south of the Ewaso Ng'iro River in central Kenya or west of the Tana River in eastern Kenya. They questioned whether the common warthog and the desert warthog might be sympatric at some sites. d'Huart & Grubb (2005) produced a photographic guide that highlights the diagnostic differences between the common warthog and the desert warthog. Some of the main diagnostic phenotypic characters used to identify the two species of warthog in the field are as follows: common warthogs have pointed ear tips, cone-shaped genal warts, a 'diabolo-shaped' head (when viewed from the front), and the suborbital areas are not swollen (fig. 1); desert warthogs have ear tips that are lax and flipped back, hook-shaped genal warts, an 'egg-shaped' head (when viewed from the front), and swollen suborbital areas (fig. 2) In 2005, we started to opportunistically collect distribution data for both species of warthog in Kenya. TMB and YdJ found desert warthogs 15 km and 80 km west of Garissa town in 2005 when they encountered two solitary individuals in medium-dense Acacia bushland during a primate survey. These are the first records west of the Tana River and extend the geographic range to ca. 265 km northwest of Mkok-oni, the nearest locality mentioned by d'Huart & Grubb (2001).
Yvonne A. de Jong
added a research item
Two species of warthogs are present in eastern Africa; the common warthog Phacochoerus africanus (Gmelin 1788), and the desert warthog Phacochoerus aethiopicus (Pallas 1766). A good understanding of the biogeography, abundance, habitat requirements, ecology, and behavior of the poorly known P. aethiopicus is important to the development of effective conservation and management plans for this species. The primary objectives of this Project were to: (1) obtain information on the distribution and abundance of P. aethiopicus and P. africanus in northern Kenya; (2) establish a baseline against which long-term trends in distribution and abundance of both species can be determined; (3) obtain ecological and behavioral data; and (4) assess the conservation status of both species in the region. Rapid assessment methods were used to determine distribution and relative abundance of each species. The extent of occurrence of P. aethiopicus in Kenya is ca. 134,000 km² and that of P. africanus ca. 207,000 km². The encounter rate with Phacochoerus in northern Kenya was 0.006 individuals/km and 0.128 individuals/hour (n=51). Phacochoerus aethiopicus was encountered at 0.001 individuals/km and 0.015 individuals/hour (n=6), while P. africanus was encountered at 0.005 individuals/km and 0.113 individuals/hour (n=45). This Project is the first to report P. aethiopicus on the southern foothills of Mt. Forole, extending the known range 120 km to the west. This Project is also the first to validate P. africanus for the region between Lake Turkana and the Uganda border, extending the known range west of Lake Turkana 200 km to the north. No evidence was found for P. aethiopicus west of the Eastern (Gregory) Rift Valley; the known western limit is west of Baragoi (36.810°E). The two taxa are known to be sympatric at three sites; central Kenya (ca. 8,700 km²); central southern Kenya (ca. 6,900 km²); eastern Kenya (ca. 3,900 km²). The main threats to Phacochoerus, and most other wildlife, in the study area are habitat degradation, loss and fragmentation, competition with livestock, and poaching. Phacochoerus aethiopicus occurs in least eight, probably 11, protected areas. All protected areas are, however, to various degrees, affected by unsustainable, often illegal, human activities. These include poaching, livestock grazing/browsing, and farming. Numerous range and altitude extensions for taxa other than Phacochoerus were obtained during this Project, including the eastern patas monkey Erythrocebus patas pyrrhonotus, Mau Forest guereza Colobus guereza matschiei, Somali lesser galago Galago gallarum, freckled nightjar Caprimulgus tristigma, and Speke's sand lizard Heliobolus spekii.
Yvonne A. de Jong
added an update
We now updated the Phacochoerus Photographic Map using new technology, a new basemap, distribution maps for both warthog species and additional images of both taxa. The new PhotoMap can be accessed on: http://www.wildsolutions.nl/photomaps/phacochoerus/
We like to thank Arnoud the Jong for all his help with the PhotoMap!
 
Jean Pierre d'Huart
added a project goal
The rediscovery of Ph. aethiopicus in N Kenya, Ethiopia and Somalia prompted a detailed investigation on the respective distribution of the two species of warthog, with a focus on their status, habitat, diet and behaviour. Areas of sympatry help determine their distinct ecological niche and possible interspecific interactions. Joint research project with Drs Y. de Jong and T. Butynski.