Rediscovery of the Cape Warthog Phacochoerus aethiopicus : A Review

Journal of East African Natural History 99(2): 77–102 (2010)

REDISCOVERY OF THE CAPE WARTHOG PHACOCHOERUS

AETHIOPICUS: A REVIEW

Peter Grubb1 (†) c/o 82 Drewstead Road, London SW16 1AG, United Kingdom

Jean-Pierre d’Huart

14 Rue du Monty, 1320 Beauvechain, Belgium. [email protected]

ABSTRACT 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. Keywords: Phacochoerus aethiopicus, warthog systematics, geographical isolation, morphology.

INTRODUCTION For most of the 20th century, it was generally accepted that there was only one species of warthog. Checklists (Allen, 1939; Corbet & Hill, 1980; Honacki et al., 1982), general accounts of African mammals (Dorst & Dandelot, 1970; Kingdon, 1979),

1 The draft manuscript of this paper was written by the first author and given to the second author for comments shortly before Peter Grubb passed away in December 2006. This version has been finalised and updated by the second author.

78 P. Grubb & J-P. d’Huart

reviews of artiodactyls (Haltenorth, 1963, Ansell, 1972), treatises on southern African mammals (Roberts, 1951; Smithers, 1983) and a monograph on wild pigs (Mohr, 1960) all mention only a single species. On the other hand, palaeontologists distinguish two Holocene species of warthogs in Africa (Van Hoepen & Van Hoepen, 1932; Ewer, 1957a,b; Cooke & Wilkinson, 1978), recognising that one of them, in historical times confined to South Africa, is now extinct. In the following discussion it will emerge not only that the palaeontologists are correct in recognising two species, but that both species of warthogs still exist (Grubb & Oliver, 1991; Grubb, 1993, 2005; d’Huart & Grubb, 2001). Although the two-species concept may seem to be new, it has a long history, as discussed below. HISTORY OF WARTHOG SYSTEMATICS Pallas (1766) published an account of a live warthog which had been sent by the Governor of the Cape of Good Hope to William V, Prince of Orange, and which was kept in the Prince's menagerie near The Hague (currently The Netherlands). Pallas named it Aper aethiopicus and noted that this animal had no incisors. In the same year, Buffon (1766) described under the same name the skeletal remains of another warthog from Cap-Vert Peninsula (Dakar, Senegal) that, on the contrary, possessed well-developed incisors: two mesial i1 in the upper jaw and six in the lower jaw. Pennant (1771) and Erxleben (1777) were aware of these dental differences but tabulated Pallas's and Buffon's contributions on these pigs as belonging to a single species. In 1788, Gmelin provided a description and a scientific name, Sus africanus, for the Cap-Vert animal and, accordingly, listed two species of warthogs in his 13th edition of Linnaeus' Systema Naturae. For the next 130 years, following Pallas and Gmelin, two species of warthogs at first called Sus aethiopicus and Sus africanus were almost universally recognised (Lönnberg, 1908).

Frédéric Cuvier (1810) appreciated that warthogs were a distinct group of wild pigs because of their specialised cheek teeth and coined “le genre Phacochaere” [sic]. G. Cuvier (1816) referred them to ‘les Phaco-Choeres’ and explained that this was from “Phaco choerus”, a pig bearing a wart. However, whether he can be said to have designated a scientific name is disputed (Ellerman et al., 1953); to designate a genus, the name Phacochoerus first appears in F. Cuvier 1826 (Morrison-Scott, 1955; International Commission on Zoological Nomenclature, 1957).

Thunberg (1811), in his Mammalia Capensia, mentioned both Sus aethiopicus and Sus africanus, but the latter was the bushpig, which had not yet been given a valid scientific name. Thunberg did not know of warthogs with incisors as they had not yet been recorded from the Cape Colony. However, they were soon found in the north-eastern part of Africa, in Eritrea, and named as Phascochoeres [sic] aeliani Cretzchmar, 1826, after the Roman naturalist, or Phacelochoerus [sic] haroia by Hemprich & Ehrenberg (1833), providing a new genus and species for the Eritrean warthog. For the sake of clarity, Geoffroy St Hilaire (1828) referred to P. aethiopicus and P. africanus as P. edentatus and P. incisivus, respectively, though these junior synonyms never acquired any currency. van der Hoeven (1839) referred to the edentulous species as Phacochoerus pallasii [sic] in recognition of its original

Rediscovery of the Cape warthog Phacochoerus aethiopicus 79

describer. The species nomens ‘aeliani’ and ‘pallasii’, and the vernacular Aelian's warthog and Pallas's warthog, were widely used in subsequent literature so that when Sundevall (1846) reported warthogs with incisors from Natal (South Africa) for the first time, he assigned them to Sus (Phacochoerus) aeliani. Jardine (1836) distinguished Aelian's warthog (Phascochaeres [sic] aeliani) from the Cape warthog, which he referred to as Phascochoeres larvatus.

For over 100 years, numerous authors listed two species of warthog in their compendia, whether original or based on the works of Linnaeus or Cuvier, including Pennant (1781), Kerr (1792), Link (1795), G. Shaw (1801), Turton (1806), G. Fischer (1814), Griffith et al. (1827), I. Geoffroy St Hilaire (1828), J. B. Fischer (1829), Schreber (1835), Jardine (1836), Reichenbach (1846), Giebel (1853) and Trouessart (1898). While these authors recognised the dental differences between the species, G. Cuvier (1816) remained uncommitted, stating that dental differences could reflect ageing or might be specific characters, and acknowledging at the same time distinctions based on skull shape. Most cataloguers of museum collections indicated that they knew of the differences in incisor development among warthogs, though they did not always identified their specimens correctly. Other cataloguers of the same material, however, rejected the two-species taxonomy (Gray, 1868, 1873; Lydekker, 1915).

Anatomists, zoologists and palaeontologists affirmed that there were two recent species of warthog, and also conducted original studies of osteological material in reaching their conclusions or had even examined living animals: F. Cuvier (1810, 1822, 1825, 1826), van der Hoeven (1839), Owen (1845, 1850, 1851), P. L. Sclater (1869, 1871), Blanford (1870), Lönnberg (1908), Van Hoepen & Van Hoepen (1932) and Ewer (1957b). With the description of the Somali warthog, no fewer than three species were recognised, (Lönnberg, 1909; Heller, 1914; Roosevelt & Heller, 1915; Schwarz, 1920; Hollister, 1924), though Lönnberg's taxonomy obscured his systematic conclusions.

These objections to the two-species taxonomy are described at some length because they appear to represent the only published evidence opposing a view that was otherwise widely held among anatomists and naturalists in the 19th century. Furthermore, some authors like de Blainville (1847) or Gray (1870a, 1870b) expressed their opinions in a dispassionate manner. Indeed, Gray became involved in an intemperate dispute with P. L. Sclater (1869, 1870, 1871) over the species problem in warthogs. For whatever reason, their views do not seem to have found support. The move towards a single-species consensus eventually occurred independently, without any firm substantiating evidence being published. A rather vague uncertainty began to be expressed concerning the two species concept, for instance by Flower & Lydekker (1891), Lydekker (1893, 1908), Vaughan Kirby (1899) and W. L. Sclater (1900), though in a publication dated 1894, Lydekker still clearly espoused the view that Aelian's and Pallas's warthogs were distinct species.

In 1908, Lönnberg named two new taxa of warthog: P. sundevallii (from Natal) and P. massaicus (Meru, Tanzania). After tabulating these names binomially, together with P. africanus (Senegal) and P. aeliani (Eritrea), he stated that they were 'geographic subspecies' of P. africanus, specifically distinct from P. aethiopicus. Nevertheless, he continued to list them all binomially in the rest of his paper and in


another publication (Lönnberg, 1909), where an additional form was described, the Somali warthog P. delamerei. Not until later (Lönnberg, 1917) did he assign taxa of incisor-bearing warthogs trinomially to subspecies of the species P. africanus. In the mean time, and without providing any real discussion of the evidence, Lydekker (1908, 1911, 1915) treated all the taxa of warthogs listed by Lönnberg as subspecies of a single polytypic species for which he used the prior name P. aethiopicus.

Figure 1. The common warthog Phacochoerus africanus (above), and the desert warthog Phacochoerus aethiopicus (below). Drawing by Stephen Nash.


The second decade of the 20th century witnessed considerable activity in the

description of African ungulates. With the increasing availability of specimens for scientific study and the development of the polytypic species concept, the number of ungulate taxa referred to subspecies rose from less than 30 in a whole decade (the 1890s) to a peak of more than 40 in 1913 alone (Allen, 1939). In the face of these developments, and Lönnberg's vacillation in adopting the use of trinomials, it is hardly surprising that Lydekker acted as he did and the two-species hypothesis for warthogs became obscured almost completely. Heller (1914), Roosevelt & Heller (1915), Schwarz (1920) and Hollister (1924) continued to support the two-species taxonomy—with the addition of P. delamerei as a third species—but many authors came to recognise only a single polytypic species of warthog in South Africa or southern Africa (Fitzsimons, 1920; Roberts, 1951; Ellerman et al., 1953; Smithers, 1983, Meester et al., 1986), in East Africa (Kingdon, 1979) or in Africa as a whole (Allen, 1939; Haltenorth, 1963; Ansell, 1972). Smithers (1983) even stated that the species P. aethiopicus had originally been described from a specimen from Guinea. Harper (1945) did not mention the Cape warthog at all in his review of rare or extinct mammals of the Old World, nor did Smithers (1986) in the South African Red Data Book. Our knowledge of warthogs had been extended by the discovery of specimens without incisors in East Africa and by the identification of both P. aethiopicus and P. africanus among South African fossil material, but this information did not affect zoologists' generally accepted understanding of warthog biology.

Warthogs without incisors had first been noticed outside South Africa by Elliot (1897) who obtained specimens with and without incisors from northern Somalia. He stated that for specimens without upper incisors but with the lower incisors either 'just emerging' or absent altogether ‘the idea of two species can not be for a moment entertained’, since both types were reportedly found in one sounder (a fact that is contradicted by the Chicago Field Museum records). But he did not address the issue of conspecificity between these specimens and others having a full complement of upper and lower incisors, assigning all to P. africanus aeliani without further comment. Later Lönnberg (1909) noted two skulls collected by Lord Delamere (figure 2), which also lacked upper incisors. At first he thought that they originated from the Cape of Good Hope but when he was informed that they had been obtained in Somalia, he claimed there were differences from Cape warthog skulls and supposed ‘the analogy between the Wart-Hogs of the Cape and Somaliland depends upon similar natural conditions of the two countries’ and that in Somalia the species had ‘independently reached a similar stage of specialization’.

He described the new species as Phacochoerus delamerei (Lönnberg 1909). Lydekker (1911) echoed Lönnberg’s conclusions. Heller (1914), Roosevelt & Heller (1915) and Hollister (1924) reported further specimens of P. delamerei from Kenya and commented on the characters of this taxon which they also treated as a species. Roosevelt & Heller (1915) were the only authors to recognise an interesting discontinuous distribution; they wrote ‘We have thus among wart-hogs a peculiar condition of distribution, not duplicated by other game mammals, consisting of two species [P. aethiopicus and P. delamerei], closely allied, living at opposite extremities of the range of the genus with the intermediate territory occupied by a distantly related species [P. africanus] showing considerably less specialization.’ Schwartz (1920)


commented on the specialised nature of P. aethiopicus and P. delamerei when compared with the more widespread P. africanus. Lydekker (1915) and St Leger (1935) reported what they claimed were additional specimens of P. delamerei but which on re-examination turned out to be P. africanus (d’Huart & Grubb, 2001). The name was reduced to subspecific status within the single species of warthog recognised by Lydekker (1911, 1915). This was followed by Allen (1939) and De Beaux (1922, 1924), who described correctly identified specimens from Somalia. Phacochoerus africanus delamerei was then unaccountably reduced further to the synonymy of P. aethiopicus aeliani by Haltenorth (1963). Subsequently, the Somali warthog has received virtually no recognition and had effectively disappeared from the taxonomic records.

Figure 2. A specimen of Phacochoerus aethiopicus delamerei collected by Hugh Cholmondeley (Lord Delamere) during one of his annual hunting trips in Somaliland between 1891 and 1895. Reproduced from Lydekker (1908). FOSSIL WARTHOGS Meanwhile, fossil remains of warthogs had been discovered in various parts of Africa. Pomel (1897) named Phacochoerus mauritanicus and P. barbarus from Algeria. Van Straelen (1924) described P. congolensis from Katanga, Democratic Republic of Congo. Pia (1930) described a fossil pig from Namibia as P. stenobunus. Dreyer &


Lyle (1931) described fossil pigs from Florisbad and other South African sites, naming P. helmei, P. venteri, P. meiringi and P. dreyeri. Van Hoepen & Van Hoepen (1932) showed that these specimens could be assigned to Recent taxa, including the extinct Cape warthog. They studied a skull of the latter, identified as the true P. aethiopicus by criteria cited by Lönnberg (1909), and found that both it and some of the fossil material could be distinguished (by characters of the third molar) from other fossils and most of the recent skulls available to them, these latter all being assigned to P. africanus. They regarded P. stenobunus, P. venteri and P. meiringi as synonyms of P. aethiopicus, and were followed by J.C.M. Shaw (1939) and Ewer (1957a). Van Hoepen & Van Hoepen (1932) also described a new species P. laticolumnatus. Wells et al. (1942) and Cooke (1949a, 1949b) continued to treat P. helmei as a separate species, though related to P. africanus. Cooke (1949a) reduced P. laticolumnatus to the synonymy of P. helmei. Ewer (1957a) treated P. helmei as a palaeosubspecies of P. africanus. She confirmed (Ewer, 1957b) that the skull studied by the Van Hoepens was of a Cape warthog, P. aethiopicus sensu stricto, and found more distinguishing features of the species through the examination of this specimen and further Recent and subfossil material. Finally, Cooke & Wilkinson (1978), in their review of African fossil pigs, continued to recognise the two species, P. africanus (in which they included P. congolensis) and P. aethiopicus, from fossil or sub-Recent material. Thus, while the Cape warthog has been virtually forgotten by most biologists, it is considered a valid species by palaeontologists. INCISORS AND THE TWO SPECIES OF WARTHOG Although two species of warthog were first distinguished by the presence or absence of incisors, the distinction is not as simple as first assumed. Consequently, a certain amount of confusion developed in the literature, leading to doubts about the two-species taxonomy. Frédéric Cuvier (1810) had asserted that the absence of incisors in P. aethiopicus was not due to wear. Later he stated (F. Cuvier, 1822) that the premaxilla is too thin to bear incisor roots and that if the four alveoli in the lower jaw of his specimen had ever been occupied by incisors, these must have been mere rudiments. He had seen a skull of a subadult warthog in the Royal College of Surgeons (illustrated by Home, 1799) that lacked upper incisors and yet the cheek teeth had not fully erupted. Frédéric Cuvier, therefore, implied that the Cape warthog did not necessarily lack incisors altogether and at the same time confirmed his earlier assertion that diminution or absence of incisors in this species was not merely due to wear with age. Owen (1850) later confirmed F. Cuvier's assessment and illustrated its dentition once again, but more accurately. In his influential Règne Animal, Georges Cuvier (1816) described the lower incisors of P. aethiopicus as mere vestiges, but was less assertive than his brother Frédéric. He thought that the state of the lower incisors might be due to age (presumably through abrasion) but could alternatively be a specific character, as there were also differences from P. africanus in the shape of the skull. Desmarest (1822) noted G. Cuvier’s observations and then stated that the incisors fall out in aged animals, without presenting any new evidence. Lesson (1827)


gave the number of incisors as either 2/6 or 0/0 for what at the time he regarded as a single species. Smith (1834) stated 'The two intermediate lower incisors [are] smaller than the rest, and apart from each other' for his composite species. van der Hoeven (1839) published accurate drawings of P. aethiopicus dentaries, including one in which less than a third of the columns of the last molars had commenced wear, and which was hence not fully adult, yet in which the lower incisors were tiny and vestigial. In none of his five specimens were upper incisors present. He described clearly how the minute incisors, when they persisted, differed from those of P. africanus. Reichenbach (1846) distinguished the species by their dental formulae: P. aeliani (= P. africanus) had 1/3 incisors and P. aethiopicus 0/0 incisors on each side.

de Blainville (1847) was not convinced that incisors were lacking in young P. aethiopicus and attributed the differences between the nominal species to age. In the plates accompanying his treatise, he demonstrated a supposed series of dentaries and premaxillae purporting to show wear and then loss of the lower incisors. However the cheek teeth of the allegedly later stages of wear were not included in the drawings, so it can not be seen whether they too showed evidence of increasing wear. de Blainville cited the assessments of F. Cuvier (1822) but did not seem disposed to accept them, and he did not refer to van der Hoeven's (1839) paper. He was at pains to stress that G. Cuvier (1816) had not altered his ambivalent views on the question of species status in warthogs in later editions of his famous book, seemingly taking this to be a support for his own (de Blainville's) opinions.

Owen (1845) found that the traces of four small incisors were almost obliterated in a lower jaw of P. aethiopicus which he examined. When dissecting a female Cape warthog from the Zoological Society of London, he (Owen, 1851) found no incisors in the upper jaw and four rudiments in the lower jaw that had never erupted.

Gray (1868, 1873) noticed that in one warthog skull (BM 719d), now known to be a P. aethiopicus, the lower incisors were nearly worn away to the roots and were only 'form indications'. He certainly appreciated that the presence or absence of incisors did not reflect age (Gray, 1868) but assumed that warthogs showed individual variation in the expression of incisors. Other authors were ambivalent when describing the incisors. Flower & Garson (1884), Flower & Lydekker (1891), and Lydekker (1908) said the upper incisors are absent or shed in the Cape warthog and the lower ones are worn down to the roots. Yet Flower & Garson (1884) gave the incisive formula for the genus as 1/2 or 3, Flower & Lydekker (1891) and W.L. Sclater (1900) as 1/3, tooth reduction being most complete in P. aethiopicus according to W.L. Sclater. These authors all stated that many of the teeth have a tendency to be lost with increasing age, which is certainly true for the cheek teeth. Other publications gave 1/3 as the incisive formula for the single species they recognised, such as Lydekker (1915) who stated that some of the lower anterior teeth were usually retained in old age in P. a. aethiopicus (treated merely as the nominate subspecies). Roberts (1951) affirmed that there was normally one pair of upper incisors, three of lower, though often the uppers and single ones or pairs in the lowers were lost in advanced age. Smithers (1983) gave a formula of 1/2-3 which may reduce to 0/0 'in old adults'. Even more recently Anderson & Jones (1984) cited an incisive formula of 1/3 for the genus.

Van Hoepen & Van Hoepen (1932) found that the incisors were greatly reduced in


their P. aethiopicus skull. Indeed, a photograph in Ewer (1957b) of the lower jaw, and her own observations confirm that both upper and lower incisors are absent. Cooke (1949b) mentioned that P. aethiopicus was said by Owen (1845) to lack upper incisors but 'The evidence in support of this conclusion is ... rather slender and it can hardly be regarded as a distinctive character'. Cooke was nevertheless an advocate of the two-species concept. Ewer (1957b) found that the upper incisors were absent and the lower ones were 'worn off level with the bone' or 'minute vestiges' in two other Cape skulls. Cooke & Wilkinson (1978) admitted the loss of upper incisors in P. aethiopicus and 'possibly' some reduction in the lower incisors.

Comments on incisors of Somali warthogs have also been made. Elliot (1897) mentioned that in some specimens, upper incisors were absent and lower incisors absent or 'just emerging'. Roosevelt & Heller (1915) noted that the upper incisors were not even represented by rudiments in young a few months of age, and that all lower incisors persist as rudiments sunk beneath the rim of the bone in pits well below the gum: 'These teeth are quite as rudimentary and functionless in the young as in the adults'.

The supposition that incisors, especially the lower series, become worn down with age and are eventually lost has persisted in the discussion of warthog systematics even among those who have accepted a two-species concept and it has tended to obscure interspecific distinctions. Yet perceptive observers (F. Cuvier, 1810, 1822; van der Hoeven, 1839; Owen, 1845, 1851; Ewer, 1957b) were aware of discrete differences among warthogs in the morphology of these teeth and, therefore, that distinct species could be discriminated using this feature alone. Probably only van der Hoeven (1839) went as far as to make an explicit comparison between the two categories of incisor expression. Since his paper - written in Latin - was never properly quoted, it is not surprising that uncertainty about the dentition of warthogs has persisted until the present.

In all respects, the Somali warthog resembles the Cape warthog and it will be treated as a subspecies of the latter. A vernacular name 'desert warthog' is now being used for the Cape/Somali species, P. aethiopicus (Oliver, 1993; d’Huart et al., 2008; Skead, 2011) and is convenient when reference is being made to both populations. CHARACTERS DISTINGUISHING PHACOCHOERUS AETHIOPICUS FROM P. AFRICANUS2 The upper incisors are absent in the desert warthog; this is true of all 44 specimens examined or reported in the literature (d’Huart & Grubb, 2001). For 239 skulls of mature common warthog which we have examined, 220 possessed the two upper incisors, one had a single incisor missing while 18 had none at all. Of these latter, all had clearly visible alveoli, showing that the upper incisors had once been present but had since been shed or lost post mortem. Upper incisor roots in the common warthog

2 Pictures illustrating these characters can be seen online in d’Huart & Grubb (2005).


are deep, while in the desert species it is said that the premaxilla is too thin to bear teeth (F. Cuvier, 1822; Lönnberg, 1912) and alveoli are always absent.

The lower incisors are absent or vestigial, never more than four (i1 and/or i2), in the desert warthog. When present, these teeth remain deep in the alveolus or erupt a few millimetres above the level of the dentary, are well separated, very small, no more than about 3 mm mesiodistally as measured at the crown, with very shallow roots. They are unlikely to have ever emerged above the level of the gum and come into wear. Of 24 specimens examined or described in sufficient detail in the literature, five had no lower incisors, six had only two (in two instances, i2 alone), one had three teeth and 12 had four, or their alveoli.

The adult upper and lower incisors of the common warthog have deep roots and prominent crowns which converge and make contact. The third lower incisors, when present, are bent inwards at an angle of almost 45 degrees to the other pairs. Of 225 skulls of the common warthog with lower jaws which were examined, 121 (53.8%) had six lower incisors, 21 (9.3%) had five, 75 (33.3%) had four and eight had fewer (one, two or three). The sample was not large enough for possible geographic variation in tooth frequency to be considered. In at least a third of four-toothed individuals, alveoli of the outermost (third) incisors were present, so they must have been shed naturally or lost post mortem and had not failed to erupt. If these teeth had been shed early enough, it is possible that the alveoli would have sealed up completely so that the former presence of the teeth could not be detected. As J.C.M. Shaw (1939) has already shown, lower i3 can not always be found even with X-radiography of young common warthogs, suggesting that sometimes third incisors have never been present. Insofar as a complement of five lower incisors is less frequent than one of four, there is evidently a tendency in this species to lack both the third incisors. This suggests that either these teeth are shed as a pair or they fail to develop, though not in more than 14% of cases.

In summary, the desert warthog is primarily without functional incisors, while the common warthog may lose incisors secondarily. The incisive formula is 1/2-3 for the common warthog and 0/0-2 for the desert warthog.

Ewer (1957b) recorded additional differences between the Cape warthog and the common species in the shape of the canines. Both lower and upper canines appeared to be less curved in the Cape species. The wear facet on the lower canine is differently placed, and the lower canines are less compressed.

In the Cape warthog, the large third molars are different from those of the common warthog (illustrated by Van Hoepen & Van Hoepen, 1932; Cooke, 1949b; Cooke & Wilkinson, 1978); when all the enamel columns of the tooth have come into wear, no roots have yet formed. At this stage, all the columns are of about the same length, all are able to continue growing, and even the anterior ones are still able to experience considerable wear. The life of the tooth is therefore considerably extended. This character was observed in recent material in the National Museum (Bloemfontein) and South African Museum (Cape Town) by Van Hoepen & Van Hoepen (1932) and Ewer (1957b), and is evident in some broken British Museum of Natural History skulls (81.5.11.2 or 719r; and 74a or 719t), but has yet to be confirmed in Somali warthogs. In the common warthog, roots of M3 form at the front of the tooth when the last columns reach the grinding surface or somewhat earlier. This stops further growth of the columns from front to back at a much earlier stage. The timing of root formation,


and hence the degree of hypsodonty, could vary continuously but sufficient fossil material has been studied to suggest that two discrete morphologies exist.

In the desert warthog, the zygomatic arches are more robust than in the common warthog, with larger sinuses forming a spherical inflation of the jugal (malar) just in front of its articulation with the squamosal (temporal). This character is clearly evident in both sexes, from both the Cape and countries in the Horn of Africa, but is more prominent in adult males. This trait was noted in Cape specimens by Ewer (1957b) and in Somali specimens by De Beaux (1922).

The region behind the internal nares is very different in the two species. In the common warthog, there is a cavity in the floor of the neurocranium on each side of the vomer, extending backwards and upwards so that the post-narial space is shelved off on each side by a thin layer of bone that extends forward from the back. These 'sphenoidal pits' are formed from bones of the neurocranium floor though their precise identity has yet to be established. In the desert warthog, the pits are enormously enlarged and opened out, occupying the whole area between the internal nares and the basioccipital and basisphenoid. They are vaulted, extending further up into the skull so as to deepen the vomerine ridge considerably, and they are separated from the auditory bullae only by a thin wall of bone. This formation of the neurocranium floor was noted in the Cape warthog by Lönnberg (1908) and in the Somali race by Heller (1914). Summarising the situation in the Suidae, Sus and Potamochoerus have no sphenoidal pits, Phacochoerus africanus has small pits, and Hylochoerus and P. aethiopicus have enlarged pits.

There are differences in dimensions and proportions of the head (figures 3 and 4) and skull between the two species, but both show geographic variation and sexual dimorphism, and sample sizes are still small. Compared with the nearest P. africanus population, P. aethiopicus populations have a shorter occipito-nasal length (except for males from Kenya and southern Somalia), a broader intertemporal width, and a shorter postorbital length. Interorbital width is greater or about the same, while bizygomatic width does not yet suggest any pattern (n = 21; Grubb & d’Huart, in press). Lönnberg (1908, 1909) had already noted these differences, though he had fewer specimens for study. DISTRIBUTION AND MATERIAL RECORDS OF THE CAPE WARTHOG There is little accurate information concerning the former distribution (table 1) of the Cape warthog.(See Rookmaaker (1989) and Skead (2007, 2011) for detailed locations and reference sources). According to Vosmaer (1766), the type specimen of Phacochoerus aethiopicus was obtained from “between Kaffraria and Great Namaqualand, two hundred leagues (one league is approximately 3 miles or 4.8 kilometers) from the Cape of Good Hope”. The type locality, usually restricted to Cape of Good Hope, should be appropriately amended. The locality is hardly specific but suggests the hinterland of the Karoo.

Sparrman (1783) sent a salted dried head of a warthog to the Swedish Academy of Science. He had not seen warthogs before he came to the Sondags River in Eastern Cape Province. He discussed the specimen before going on to relate his crossing of the Boesmans River farther east. Lönnberg (1908) examined the skull and confirmed its incisor-less state and other distinctive cranial features. Thus, we are certain that this is a Cape warthog.


Table 1. Preliminary inventory of specimens of the Cape warthog seen by the authors and/or reported in the literature. n. Description Original /current location Reference 1 Head and skin sent from Cape of Good

Hope in 1757. Head placed in the museum of the Prince of Orange, but depository is not identified

The Hague (?) Rookmaaker, 1992

1 Lectotype: live specimen sent by Governor R. Tulbagh in 1765 from Cape of Good Hope to the menagerie of the Prince Willem V of Orange then (1766) to the menagerie ‘Blauw Jan’ in Amsterdam

The Hague Pallas, 1766; Vosmaer, 1766; Pennant, 1781; Rookmaaker, 1992

1 Skull sent in 1772 by Governor Swellengrebel of Cape Colony to Petrus Camper in Holland

Leiden (?) Rookmaaker, 1989; R. Visser, pers. comm.

1 Sparrman's specimen, presented to the Swedish Royal Natural History Museum

Stockholm Sparrman, 1783; Lönnberg, 1908

1 Specimen in the Musée d’Histoire Naturelle which may be the lectotype transferred from The Hague

Paris E. Geoffroy St Hilaire, 1803; F. Cuvier, 1822;

1 Burchell's 1813 specimen (British Museum of Natural History)

London Burchell, 1836

2+ At least two sold from J. Brookes's collection London Brookes, 1828 1 Zoological Society of London museum

collection (since dispersed) London Waterhouse, 1838

5 Specimens presented to the German Academy of Sciences Leopoldina, Halle (at least one of which was obtained from Brookes; since lost).

? (not recorded in the Landesmuseum collection or in the archives of the Zoologisches Institut, Halle)

van der Hoeven, 1839; B. Zich and D. Weber, pers. comm.

3 Royal College of Surgeons (destroyed in World War 2)

London Home, 1799; Owen, 1850; Flower & Garson, 1884

4 Zoological Society of London's menagerie (one of which is retained as a postcranial skeleton in the British Museum of Natural History)

London Owen, 1851; P.L. Sclater, 1850, 1869, 1871

7 Skulls or parts of skulls now surviving in the British Museum of Natural History

London Gerrard, 1862; Gray, 1868, 1869, 1873; Lydekker, 1915

1 National Natural History Museum, Leiden (Camper’s specimen?)

Leiden Jentink, 1887

1 Specimen from Port Natal presented in 1843 by W.S. Sherwill to the Trustees of the Asiatic Society of Bengal for the Indian Museum

Calcutta W.L. Sclater, 1891

2 Specimens n° 21370 & 21371 of South African Museum

Cape Town W.L. Sclater, 1900; Ewer, 1957b

1 Specimen n° 1411 of National Museum, South Africa

Bloemfontein, Orange Free State

Van Hoepen & Van Hoepen, 1932; Ewer, 1957b

1 Specimen n° 11828/9801 of Smithsonian National Museum of Natural History collected in May 1871 by J.H. Taylor in “South Africa”

Washington, D.C. R. Cuddahee, pers. comm.


Figure 3. Adult male common warthog Phacochoerus africanus on the plains of the Laikipia Plateau, central Kenya. Note the pointed ears, the cone-shaped warts, the ‘diabolo-shaped’ head, and the lack of swelling of the suborbital area. Photograph by Y. de Jong & T. Butynski.

Figure 4. Adult male desert warthog Phacochoerus aethiopicus in medium-dense shrub in Tsavo West National Park, southern Kenya. Note the flipped-back ear tips, the hooked warts, the broad, ‘egg-shaped’, head, and the swollen suborbital area. Photograph by Y. de Jong & T. Butynski

Levaillant (1795) described his shooting a warthog in the vicinity of the Fish River, a

tributary of the lower Orange in Great Namaqualand (southern Namibia). He gave a detailed description of the animal in which he stated that it lacked incisors. This is potentially a most interesting record, extending the distribution of the species far to the north-west. Unfortunately, Levaillant did not keep a journal and did not give a wholly reliable account of his exploration (Forbes, 1973). It is possible that his description was supplemented by consulting the works of Pallas or Vosmaer, especially on the crucial issue of the lack of incisors, which he could have done in the 1780s when he visited Amsterdam. There is no explicit evidence that his account is plagiarised. The figure accompanying the text, derived from one of his water-colours (Meester, 1973), is original, not a reworking of Aart Schouman's illustration of the type (Tuijn & van der Feen, 1969), as used by Pallas (1766) and others. W.L. Sclater (1900) mentioned a skull apparently of P. aethiopicus from 'Damaraland'. Apart from these two rather unsatisfactory records, there seems to be no indication of the species occurring in Namibia.

Burchell (1823) shows a locality 'Wild-boar Station' on the map of his journey, where he obtained a male warthog on 27 February 1813 (Burchell, 1836). The specimen was sent to the British Museum. The skin has been discarded but the skull survives and is certainly that of a Cape warthog. The locality is on the 'upper Orange


River', probably upstream from Hopetown, but the exact locality is not clear as Burchell's narrative did not cover his travels in this area.

van der Hoeven (1839) reported that one of his Cape warthog specimens was said to have come from Ashantee in Guinea (that is, present day Ghana). It was obtained from the 'Englishman Brookes', presumably the anatomy teacher Joshua Brookes whose famous collection had been sold a decade earlier (Brookes, 1828). The reliability of the locality can hardly be accepted in view of the early date and absence of circumstantial evidence.

Live Cape warthogs were obtained by the Zoological Society of London in 1850 and 1866 from Port Natal (Durban, RSA) and Natal (P.L. Sclater, 1850, 1869). Their incisor-less state was confirmed by Owen (1851) and P.L. Sclater (1871). As they were quite young when captured, it seems unlikely that they would have survived a long journey to the coast and may have been obtained a moderate distance inland. W.L. Sclater (1891) reported a skull attributed to the Cape warthog from Port Natal, perhaps further evidence that the species occurred this far east.

Du Plessis (1969), Skead (1980-1987, 2007), and Rookmaaker (1989) cited additional records of warthogs—possibly the Cape species—from the Cape Province. In spite of being easily observed and identified, there is surprisingly little evidence for warthogs being seen by the earlier European explorers and naturalists, and many references to wild pigs do not distinguish between warthogs and feral domestic pigs or bushpigs (Skead, 2007). Possibly the Cape warthog was never abundant (Ewer, 1957b) in historic times.

Not more than 32 specimens have thus been recorded. Some of these specimens have been lost or destroyed but there are probably more to be discovered.

In the early part of the 19th century, both species of warthog were probably equally represented in cabinets and museums. The Cape species was last recorded from the wild in 1871 (specimen in the Smithsonian) at a time when the range of the common warthog was still not fully known.

After its discovery in Senegal and its distinction from the Cape warthog in 1788, the existence of the common warthog was reported from most of the African countries during the 19th century (table 2). In 1850, Owen was able to distinguish it from the Cape species, both on the basis of morphology and distribution. The common warthog (Owen called it P. aeliani) emanated from Nubia, while the Cape warthog (Owen's P. pallasii) was known from the Cape. So the extent to which Phacochoerus africanus could be envisaged as the ‘common warthog’ only became evident once no new records of the Cape warthog were forthcoming, providing further reason for the apparent eclipse of the Cape species.

DISTRIBUTION AND MATERIAL RECORDS OF THE SOMALI WARTHOG3 The type locality of Phacochoerus aethiopicus delamerei is not certainly known. Lord Delamere told Lönnberg (1912) that he obtained the syntypical skulls from 'the country north of Guaso Nyiri' (Ewaso Ng'iro or Ewaso N’yiro or Ewaso Nyiro river) in central and east-central Kenya, but they had originally been thought to have come from Somalia (Lönnberg, 1909). A photograph by Delamere of a warthog boar from

3 d'Huart & Grubb (2001) provide details of museum references, collectors, co-ordinates, and a map for locations listed in this section.


the “Onoonoff Plain” was published earlier (Inverarity, 1899). This may be the true collecting locality, but there is no independent confirmation. Elliot (1897) obtained three warthogs without incisors (CFMNH #1292/4) from the “Anouf Prairie”. “Onoonoff Plain” and “Anouf Prairie” may both be the Ununuf Plain in northern Somalia. De Beaux (1922, 1924) reported further specimens of the Somali warthog from Dolo in southern Ethiopia, and from Gondod near Lugh, along the Juba River in Somalia. Heller (1914) and Hollister (1924) reported two specimens from (Lago) Merelle, a seasonal stream on the road to Marsabit, Kenya. In 2000, the total number of Somali warthog specimens reliably reported in the literature was only 11, but new material has since been collected in the field and donated to the National Museum of Kenya, Nairobi. Three additional specimens have also been traced in American museum collections: SMNH #308850 from Bura and USMN #187804/5 from Galma Galla, both localities situated on the east bank of Tana River, south-eastern Kenya. Table 2. Succession of early records of common warthogs P. africanus in Africa. Country Description Author “South East Africa” Skull being part of the Tradescant

collection donated to the Ashmolean Museum in 1683 and transferred in 1860 to the Oxford University Museum of Natural History: specimen Ref. n° 17499*

M. Nowak-Kemp, comm.pers.

Senegal Lectotype collected from Cap-Vert Peninsula in 1766 but treated as Aper aethiopicus until Gmelin named it Sus africanus

Buffon, 1766; Gmelin, 1788

Eritrea Specimens collected by Eduard Rüppell

Cretzschmar, 1826; Hemprich & Ehrenberg,1833

South Africa Specimens collected by Johan Wahlberg in Natal

Sundevall, 1846

Abyssinia (Ethiopia) and Cordofan (Kordofan, Sudan)

Owen, 1850

Mozambique Peters, 1852 Uganda Specimen collected in 1878 by J.A.

Baker; Oxford University Museum n°19300

M. Nowak-Kemp, comm.pers

Nigeria in 1865, Mashonaland (Zimbabwe) in 1883, Nyasaland (Malawi) in 1891, north-west Rhodesia (Zambia) in 1893, and British East Africa (Kenya) in 1908

Specimens from various collectors in the British Museum of Natural History collection

Lydekker, 1915

Ghana Jentink, 1887 Tanganyika (Tanzania) Matschie, 1895 Somaliland (N Somalia) Specimens collected in Mandheera

and Hullier. Chicago Field Museum: specimens n° 1290, 1291, 1295

Elliot, 1897; J. Kerbis, pers. comm.

*This particular specimen is the oldest museum specimen of Phacochoerus recorded. As first specimen of P. africanus ever collected, it predates Gmelin’s description of the common warthog by 105 years. A specific note on this discovery is in preparation.


Not all warthogs from Somalia belong to the desert species. Dr R.E. Drake-

Brockman obtained common warthogs at Shimbiraleh Guban, 30 miles SW of Berbera, and near Elan Gubati near Lower Sheikh, which were misidentified as P. a. delamerei by Lydekker (1915) and St Leger (1935), respectively. Elliot (1897) obtained common warthog at Mandheera and Hullier. These few records suggest an enclave or narrow extension of the common warthog to mountainous areas within the lowland, arid range of the Somali warthog.

Since 2000, the taxonomic status of warthogs has been updated in Ogaden, southeastern Ethiopia (Wilhelmi et al., 2004), in southern Djibouti (Künzel et al., 2004), and especially in Kenya (Culverwell et al., 2008; de Jong et al., 2009), where field investigations reveal for the first time the presence of desert warthogs south of the Ewaso Ng’iro River and west of the Tana River River, as far southwest as the western part of Tsavo West National Park near the border with Tanzania (where P. aethiopicus and P. africanus are sympatric). The conservation status of P. aethiopicus has been assessed and an updated distribution map compiled for IUCN’s Global Mammal Assessment (d’Huart et al., 2008). CONCLUSION In reviewing and reconsidering the status of the Cape warthog, it is concluded that this species is morphologically distinct from the common warthog, from which it differs in a number of trenchant and functionally unrelated characters. As far as we know, these are shared by the Somali warthog, which must be regarded as a subspecies of the Cape warthog, the two together being termed the ‘desert warthog’.Why has this position not been made clear before? Many cranial and dental characters differentiating Phacochoerus aethiopicus have been published but at various times, sometimes briefly; had not all been established as diagnostic; and had not all been taken into account by any one author. Specimens of the Cape warthog stopped becoming available while more and more material of the common warthog was being acquired, shifting the naming of warthogs to this species alone. The discovery of the Somali warthog came at a time of confusion when trinomials were first being applied to large African game animals, and its connection with the Cape population was forgotten, never being noticed again in any reviews of the African fauna. Critical comparisons between Cape, Somali and common warthogs were not repeated after Hollister's (1924) brief note.

After the “rediscovery” of the Cape warthog (Grubb & Oliver, 1991) and the priority research projects recommended by the IUCN/SSC Pigs, Peccaries and Hippos Specialist Group (Grubb, 1993; d’Huart & Oliver 1993), a significant amount of new information has been gathered. Based on reliable data in the literature, direct observations and new material collected in the field, a first assessment of the distribution of the two species in the Horn of Africa was presented and discussed in d'Huart & Grubb (2001). DNA analysis shows that common and desert warthogs belong to two genetically distinct lineages that diverged for approximately 4.5 myr, originating in the last part of the Pliocene (Randi et al., 2002).


Figure 5. Approximate distribution of the extinct Cape warthog Phacochoerus aethiopicus aethiopicus and of the extant Somali warthog Phacochoerus a. delamerei. Sources: Rookmaaker (1989) and Skead (2007) for Cape warthog; d’Huart et al. (2008) for Somali warthog.

The disjunct distribution of the two forms of desert warthog (figure 5) is matched

by approximately 10% of the southern African sub-region mammal species, such as the black-backed jackal Canis mesomelas Schreber, 1775, the bat-eared fox Otocyon megalotis (Desmarest, 1822), the aardwolf Proteles cristata (Sparrman, 1783) and Kirk’s dikdik Madoqua kirkii (Günther, 1880) (Smithers, 1983; Grubb et al., 1999). According to Coe & Skinner (1993), such discontinuous distribution suggests that the original ranges were significantly influenced by both the southwards migration of pastoralists with their stock and by the naturally-mediated climate change. These factors may have had a profound effect on the distribution of major vegetation types and, therefore, on the composition of faunas. Archaeological evidence from East Africa indicates that during the last 12000 years, large mammals of the arid zones were found much farther south, but that significant patterns of local extinction were associated with these distribution changes.


The introduction in the late 1960s of the common warthog in the Western, Eastern,

and Northern Cape (south of the Orange River), including in the former habitat of the extinct Cape warthog, induced an exponential growth in numbers which awarded an ‘invasive’ status and called for the eradication of the species in that region. Investigations on the reasons for the success of the introduced common warthog, included a comparison of the diets of the two species and revealed that both P. aethiopicus, with no functional incisors, and the P. africanus, equipped with a full set of functional incisors, were mainly grazers, but that the former had a larger proportion of browse in its diet, thereby possibly gaining a foraging advantage over the Cape warthog. As a generalist species, the common warthog is able to shift its diet during nutrient-limited conditions and is better adapted to exploit new habitats (Nyafu, 2009).

The rediscovery of the Cape warthog in eastern Africa provides an interesting array of new research areas and conservation challenges related to, for example, the respective distribution of P. aethiopicus and P. africanus and the question of sympatry, parapatry and ecological segregation; their respective biology, ecology and behaviour in shared habitats; and the comparison between P. a. aethiopicus and P. a. delamerei for dental, cranial and skeletal differences, as well as DNA analysis, in order to assess the true extent of their genetic divergence. ACKNOWLEDGMENTS The present review has benefitted from the cooperation of the following individuals who have kindly contributed to the collection of data: A. Boshoff (Nelson Mandela Metropolitan University, Centre for African Conservation Ecology, Port Elizabeth, RSA), Tom Butynski and Yvonne de Jong (Eastern Africa Primate Diversity and Conservation Program, Kenya), Rebecca Cuddahee (Department of Evolutionary Anthropology, Duke University, Durham, USA) , Julian C. Kerbis Peterhans (Adjunct Curator, Mammals, Department of Zoology, Chicago Field Museum, USA), Malgosia Nowak-Kemp (Collections Manager, Zoological Collections, Oxford University Museum of Natural History, UK), L.C. Rookmaaker (Senior Research Fellow, National University of Singapore, Chief Editor of the Rhino Resource Center), R.P.W. Visser (Utrecht University, The Netherlands), Danny Weber (Head of Archive, Deutsche Akademie der Naturforscher Leopoldina, Halle, Germany), Bernhard Zich (Abteilungsleiter, Landesmuseum für Vorgeschichte, Halle, Germany) and two anonymous reviewers. The authors thank them wholeheartedly. REFERENCES Allen, G.M. (1939). A checklist of African mammals. Bulletin of the Museum of

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Rediscovery of the Cape Warthog Phacochoerus aethiopicus : A Review

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