Aardvark habits and traces

Aardvarks leave clear signs of their presence (Gutteridge and Liebenberg, Reference Gutteridge and Liebenberg2021). Consideration of the habits and attributes of extant aardvarks, coupled with a review of the traces they create, enable an understanding of the type of evidence potentially preserved in the paleoichnology record.

Aardvarks (Fig. 9A) are seldom-seen, nocturnal, solitary creatures, weighing as much as 65 kg (Gutteridge and Liebenberg, Reference Gutteridge and Liebenberg2021). Distinctive anatomical features include a long snout (often referred to as ‘pig-like,’ e.g., Liebenberg, Reference Liebenberg2000), large ears (often referred to as ‘donkey-like,’ e.g., Liebenberg, Reference Liebenberg2000), and a long, thick, tapering tail (Shoshani et al., Reference Shoshani, Goldman and Thewissen1988). Other physical attributes include a stocky body, short neck, and arched back (Shoshani et al., Reference Shoshani, Goldman and Thewissen1988). Sturdy legs and feet with long, robust claws are characteristic. The forelimbs are short and particularly powerful, allowing for subterranean digging at great speed (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017; Walker Reference Walker2018). Melton (Reference Melton1976) reported that a 1-m-long burrow could be dug within five minutes. Stuart and Stuart (Reference Stuart and Stuart2019) referred to the aardvark as the ‘master digger’ and noted that it occurs anywhere in sub-Saharan Africa where its preferred diet of termites and ants is available.

Figure 9.

(A) The aardvark, Orycteropus afer. (B) An aardvark track, showing the distinctive tridactyl morphology; typical aardvark tracks are ∼8–10 cm in length. (C) Two adjacent aardvark burrows in the Karoo region of South Africa, in a pattern resembling the findings at sites 1, 2, and 3; scale bar = 10 cm. (D) An aardvark burrow in the Karoo region of South Africa, with an arrow indicating claw scratch marks in a pattern resembling the findings at sites 4 and 5; horizontal white scale = 50 cm. Images (A) and (B) reproduced with permission from Mathilde Stuart.

Southern African tracking guides indicate that aardvark tracks (Fig. 9B) are distinctive and readily recognizable (Liebenberg, Reference Liebenberg2000; van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017; Walker, Reference Walker2018; Stuart and Stuart, Reference Stuart and Stuart2019; Gutteridge and Liebenberg, Reference Gutteridge and Liebenberg2021). Four toes are present on the forefoot, and five toes on the hindfoot. The resulting tracks, ∼8–10 cm long, are typically tridactyl and show three long toes ending (in well-preserved cases) in claws on both the slightly smaller front feet and slightly larger hind feet (Stuart and Stuart, Reference Stuart and Stuart2019). Occasionally, in soft substrates, impressions of claw V on the front foot and claws I and V on the hind foot may be registered; the hind foot is usually placed behind the forefoot impression, although it may be partially superimposed on it in an imperfect direct register (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017). A tail drag may be evident in soft substrates. Illustrations in the above-mentioned tracking guidebooks indicate that the outer digit impression of the hindfoot (digit IV), and to a lesser extent the middle digit impression (digit III), display an outward convexity. These features are not obvious in forefoot tracks.

However, burrows (Fig. 9C), rather than tracks, are the most characteristic element of aardvark traces. Stuart and Stuart (Reference Stuart and Stuart2019) described large burrows with an entrance measuring 50–80 cm in diameter, with deep grooves in the burrow walls created by the massive claws on the aardvark’s foot (Fig. 9D). Use of the tail as a support when digging was noted, resulting in a wedge-shaped impression in the soil.

Aardvark burrows may be used as permanent burrows, temporary refuges, and burrows made while foraging (Shoshani et al., Reference Shoshani, Goldman and Thewissen1988; Liebenberg, Reference Liebenberg2000). A typical feeding sign is a hole dug into the side of a termite mound (Stuart and Stuart, Reference Stuart and Stuart2019). Such holes may be deep enough to cover the aardvark completely or may be shallower and only large enough to cover the animal’s head (Shoshani et al., Reference Shoshani, Goldman and Thewissen1988). Temporary refuges tend to be shallow, but may run underground for meters (Liebenberg, Reference Liebenberg2000). Permanent burrows, in which aardvarks reside and bear young, are more complex and tend to be deeper, with multiple tunnels and several entrances. (Melton Reference Melton1976) reported that the entrance, measuring 40–50 cm in diameter, was often the narrowest part of the burrow, and that terminal chambers were as much as a meter in diameter, large enough to enable the aardvark to turn around. Burrow lengths of 5–8 meters, with smaller cavities and compartments leading off from the main chamber, have been reported by (van den Heever et al. Reference van den Heever, Mhlongo and Benadie2017) . Mounds of excavated material may accumulate beside the burrow entrance.

Use by other animals of burrows that have been abandoned by aardvarks is a common theme. (Stuart and Stuart Reference Stuart and Stuart2019) noted that warthogs (Phacochoerus africanus) occupy and modify holes dug by aardvarks, and that while porcupines (Hystrix africaeaustralis) may excavate their own burrows, they may also use and modify aardvark burrows. These species fall within the ‘secondary modifier’ category of (Kinlaw Reference Kinlaw1999). In addition, (van den Heever et al. Reference van den Heever, Mhlongo and Benadie2017) noted that disused burrows may be used by wild dogs, hyenas, honey badgers, snakes, and birds. These fall into the ‘simple occupant’ category of (Kinlaw Reference Kinlaw1999).

Aardvark scat is seldom encountered by modern trackers, as droppings tend to be covered up or buried beneath excavated soil (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017; Walker, Reference Walker2018). However, aardvark scat is distinctive, being composed of soil impregnated with the heads of termites and ants (Stuart and Stuart, Reference Stuart and Stuart2019). As such, aardvark coprolites might be readily identifiable.

In summary, traces of aardvarks that could be sought in the fossil record include tracks, tail impressions, feeding traces, burrows, and coprolites. Of these, burrows are probably the most obvious and may be the easiest to identify. An ideal case might involve a feeding burrow within a termitarium, complete with claw-scrape impressions, tracks, and an adjacent wedge-shaped tail impression.

Despite all these possibilities, it appears that until now, only a single, undated case of probable aardvark burrows has been reported. This was from Simanya, on the south bank of the Kavango River in northern Namibia, where Pickford (Reference Pickford2018, Fig. 7) described an infilled ovoid feature as much as a meter in diameter. The purported burrow penetrated poorly consolidated, pale, nodular sand and silt. The infill was formed by dark gray clayey-silty soil and fragments of the subjacent rock. The lowest portion of the burrow appeared V-shaped, suggesting modification by a porcupine or other secondary modifier.

The regional record

The historic and prehistoric distributions of aardvarks in the Western Cape and Eastern Cape provinces were extensive. Evidence includes reports of travelers and early naturalists, place names, traditional names, and the rock art record. In addition, during much of the Pleistocene the vast Palaeo-Agulhas Plain (Cleghorn et al., Reference Cleghorn, Potts, Cawthra, Cleghorn, Potts and Cawthra2020), most of which is currently submerged, was exposed south of the modern coastline and would have provided substantial extra habitat. Sites 1–4 would have been located at the margin of the Palaeo-Agulhas Plain, and there is no reason to think that the aardvark would not have utilized this habitat.

Skead (Reference Skead1987), in his monumental work on the historical distribution of mammals in the Cape Province, disclosed that aardvark records had largely been overlooked because of the species’ widespread distribution, leading to the assumption that the historic distribution range was similar to that of the present. Numerous references were noted, many of them pertaining to the dangers to horses and riders, or to wagons and carts, through unexpected encounters with aardvark burrows. Given the prevalence of termite mounds, it was concluded that aardvarks could have occurred ‘almost anywhere.’

A description by the missionary (Latrobe Reference Latrobe1818, p. 310) provides an example from the Mamre area of the Western Cape Province in 1816. In describing the risk of injury from burrows adjacent to the dwelling of a blind chief, he commented: “These singular creatures are about as large as a common pig. They have a long snout, long sharp claws, very little hair, and a rough skin. Their food is the ants, and probably other insects.” This leaves no doubt as to the identity of the burrower.

(Möller Reference Möller2017) quoted reports of names for the aardvark in a variety of San, Khoikhoi, Nama, and Korana languages, as well as place names, which in the Western Cape included ‘Beervlei,’ an Afrikaans translation of an original San term. Such records confirm the widespread distribution of the aardvark and how indigenous peoples were familiar with it.

Although depictions of aardvark are relatively rare in the rock art record, they have been recorded from at least four sites in the Western Cape Province. Aardvark paintings from Cloete’s Pass in the Little Karoo (Fig. 10A) were reproduced as the frontispiece in a rock art book (Rust, Reference Rust2012), and a probable aardvark image is reported from Sevilla in the Cederberg (Fig. 10B) (Andrew Paterson, personal communication, 11 May 2024). A painting depicting a possible aardvark was reported by (Helm et al. Reference Helm, Paterson and Rust2024a) from a Western Cape site south of the Langeberg, in close proximity to an image that might represent flying termites. The juxtaposition was regarded as potentially significant, given the dietary preferences of the aardvark. Finally, probable aardvark images from the Leeublad site in the Kammanassie Mountains in the Little Karoo are provided as Figure S1 in supplementary information. Together, these images further confirm the regional existence of aardvarks and awareness of their presence by local inhabitants, although the precise dating of San rock art can be challenging, and in certain areas such rock art was still being created in the late nineteenth century. A potential age estimate for regional rock of at least 2000 years has been provided (Deacon and Deacon, Reference Deacon and Deacon1999), while in some areas southern African rock art may be as old as 27,000 years BP (Lewis-Williams and Challis, Reference Lewis-Williams and Challis2011).

Figure 10.

(A) San rock art of aardvarks from Cloete’s Pass in the Western Cape Province, reproduced with permission from Renée Rust. (B) San rock art of a probable aardvark from the Cederberg in the Western Cape Province, reproduced with permission from Andrew Paterson.

The body fossil record

The earliest known aardvark is dated to circa 19 ka (Pickford, Reference Pickford2019), although it has been suggested that the Tubulidentata appeared in Africa during the Paleocene (Patterson, Reference Patterson1975). In southern Africa, the aardvark fossil record extends back to the Miocene, with reports of the genera Amphiorycteropus and Orycteropus from southern Namibia (Pickford, Reference Pickford1996, Reference Pickford2003, Reference Pickford2008; Avery, Reference Avery2019), and a Pliocene record from northern Namibia (Pickford et al., Reference Pickford, Mocke, Ségalen and Senut2016). Aardvarks of undetermined genera and species were reported from Early Pliocene deposits of the Sandveld Group at Langebaanweg, in the Western Cape Province near the west coast (Hendey, Reference Hendey1981). (Pickford Reference Pickford2005) suggested that they were compatible in size and most morphological details to Orycteropus afer. These are therefore the earliest fossils attributed to this species, and the extant lineage may have evolved in southern Africa (Pickford, Reference Pickford2005).

The Pleistocene and Holocene record of O. afer in southern Africa is extensive, with the type specimen being recorded by Pallas in 1766 from the Cape of Good Hope (Avery, Reference Avery2019). Pleistocene records from the Western Cape or Eastern Cape include Eland’s Bay Cave, Klasies River, Nelson Bay Cave, and Sea Harvest, while Holocene records include Nelson Bay Cave and Oudepost 1. For example, the species has been recorded in Later Stone Age archaeological deposits at Elands Bay Cave (Klein et al., Reference Klein, Avery, Cruz-Uribe and Steele2007), Pleistocene deposits at Elands Bay Cave (Klein and Cruz-Uribe, Reference Klein, Cruz-Uribe, Parkington and Hall1987), and in layers dating to 10–9 ka in Nelson Bay Cave near Plettenberg Bay (Klein, Reference Klein1972) in the Western Cape Province. Orycteropus afer has been documented in Pleistocene deposits in the Eastern Cape Province at Klasies River (Klein, Reference Klein1976). However, following excavations of Middle Stone Age and Later Stone Age deposits at Die Kelders 1 Cave near Site 1, and despite an extensive list of mammalian fauna, no aardvark records were reported (Klein and Cruz-Uribe, Reference Klein and Cruz-Uribe2000).

Differential diagnosis

In formulating a differential diagnosis for the burrow traces described here, a first question relates to any possible non-burrow explanation for the noted features. While clear claw scratch marks in the walls make a burrow identification essentially unequivocal, large tubular cavities also could have a botanical origin and could represent areas where substantial roots once existed. Indeed, rhizoliths (Klappa, Reference Klappa1980; Durand et al., Reference Durand, Monger, Canti, Verrecchia, Stoops, Marcelino and Mees2018) are a common feature in Cape coastal aeolianites and sometimes in paleosols. However, in our experience, rhizoliths usually can be distinguished by examining the appearance of the surrounding rock, which typically appears altered due to chemical interaction with the organic plant matter. If a burrow is examined in longitudinal section, it may be possible to distinguish it from a rhizolith by the tendency of rhizoliths to taper if exposed for a sufficiently long distance; however, the purported aardvark burrows described here happen to occur predominantly in cross section. Nonetheless, we contend that the features at the sites described are inconsistent with rhizoliths.

The Cape porcupine (Hystrix africaeaustralis), the largest rodent in Africa (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017), also digs, and therefore needs to be considered. (Gutteridge and Liebenberg Reference Gutteridge and Liebenberg2021) noted that the porcupine is a ‘prolific digger,’ and will dig to reach its food of roots and bulbs. They further noted that Cape porcupine burrows are V-shaped (something that is confirmed in our experience) and can be large, with smooth upper walls due to abrasion from quills (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017). (Walker Reference Walker2018) noted that the porcupine frequents disused aardvark burrows or holes that it has dug itself. It may live singly or in a group in a burrow, which has usually been taken over from an aardvark (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017). (Stuart and Stuart Reference Stuart and Stuart2019) described ‘feeding holes,’ which may contain claw marks in the walls, although never as large as those left by aardvarks (also confirmed in our experience). It is evident, then, that porcupines use aardvark burrows and create feeding holes, and when they do create their own burrows, there are no reports of them being as complex or substantial as those of aardvarks. Furthermore, the burrows are V-shaped in cross section, in contrast to the more circular shape of aardvark burrows. Porcupines are therefore unlikely candidates for the creation of any of the large fossilized burrows identified here.

Among regional extant carnivorans, jackals are discussed below and the African wild dog (Lycaon pictus) is not a burrower. Some fox species dig burrows. Among southern African species, the bat-eared fox (Otocyon megalotis) uses aardvark burrows (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017) or modifies burrows of the yellow mongoose, and on occasion may dig its own burrow; it frequently digs feeding holes, but these seldom exceed 7 cm in diameter (Stuart and Stuart, Reference Stuart and Stuart2019). The Cape fox (Vulpes chama), in contrast, is a more regular burrow digger, although it too occupies the burrows of other animals such as the yellow mongoose or springhare (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017). However, both species are small, slender carnivorans, with tracks less than 4 cm in length, compared with ∼5.5 cm for jackals and 8–10 cm for the aardvark (Stuart and Stuart, Reference Stuart and Stuart2019). They do not excavate burrows as large as those of aardvarks and are therefore also excluded.

Jackals and warthogs are sometimes thought of as burrowers, but this relates to their habit of occupying disused aardvark burrows (Walker; Reference Walker2018; Gutteridge and Liebenberg, Reference Gutteridge and Liebenberg2021). Likewise, the aardwolf (Proteles cristatus) does not dig its own burrows but occupies those of aardvarks and springhares (van den Heever et al., Reference van den Heever, Mhlongo and Benadie2017).

The springhare (Pedetes capensis) can be excluded on grounds of burrow diameter. Although these rodents certainly occurred in the Cape in historic times (Skead, Reference Skead1987), and there is no reason to think that the Pleistocene distribution range was dissimilar, their burrows are substantially smaller in diameter than those of the aardvark. (Stuart and Stuart Reference Stuart and Stuart2019) reported burrow diameters of 18–25 cm for this species.

It is not possible to disprove the possibility that an extinct fossorial species, as yet undocumented in the body fossil record, might have created the burrow traces. However, given the extensive, well-documented regional body fossil record (Avery, Reference Avery2019), this appears to be extremely unlikely.

A final question pertains to the age of the burrow at Site 5. Even if it is accepted as an aardvark burrow, the age of 126 ± 8 ka relates to the basal aeolianite layer, not the paleosol in which the burrow occurs. Furthermore, the burrow may have been dug some time after the paleosol horizon was established. If this is a matter of a few decades or even a few thousand years, it would not be significant, but could it have been dug much more recently, say within the last thousand years? We think the likelihood of such a possibility is remote, given the beach setting and the high aeolianite cliffs that occur above the burrow. Aardvarks are subsurface burrowers and have not been reported burrowing into cliff faces. This possibility can therefore be excluded.

In summary, there is no evidence to support the likelihood of any of the fossilized burrow traces reported here to have been made by anything other than aardvarks. We are confident in identifying aardvarks as the burrow makers, although the certainty of this conclusion varies from site to site.

With respect to the possible aardvark track, (van den Heever et al. Reference van den Heever, Mhlongo and Benadie2017) noted that aardvark tracks can be confused with those of warthog (Phacochoerus africanus) or bushpig (Potamochoerus larvatus), or when two partially overlapping medium-sized antelope hoof prints are registered beside each other. All three of these alternative trackmakers register didactyl tracks, and the tridactyl morphology evident at the tracksite, coupled with the absence of any other tracks of warthogs, bushpigs, or antelope, increase the likelihood that the track was registered by an aardvark. Although the track is slightly shorter than the typical, reported size range, comparison with the track morphology (Fig. 9B) establishes the close resemblance to the tracks of modern aardvarks.

Optically stimulated luminescence dating

Over the last two decades, sites on the Cape coast have been dated through optically stimulated luminescence (OSL) studies, with more than 100 ages now published for aeolianite deposits. Initial studies (e.g., Roberts et al., Reference Roberts, Bateman, Murray-Wallace, Carr and Holmes2008; Carr et al., Reference Carr, Bateman, Roberts, Murray-Wallace, Jacobs and Holmes2010; Bateman et al., Reference Bateman, Carr, Dunajko, Holmes, Roberts, Mclaren and Bryant2011; Cawthra et al., Reference Cawthra, Jacobs, Compton, Fisher, Karkanas and Marean2018; Jacobs et al., Reference Jacobs, Jones, Cawthra, Henshilwood, Roberts, Cleghorn, Potts and Cawthra2020) were followed by our own OSL dating work focused on ichnofossil-bearing sites (e.g., Helm et al., Reference Helm, Bamford, Carr, Cawthra, De Vynck, Dixon and Quick2023b, Reference Helm, Carr, Lockley, Cawthra, De Vynck, Dixon and Stear2023c, Reference Helm, Carr, Cawthra, De Vynck, Dixon, Lockley and Stear2023d, Reference Helm, Carr, Cawthra and De Vynck2024b). For the latter work, each sample was assigned a code beginning with ‘Leic’. While none of the sites described herein has been dated directly, they can be compared with nearby dated sites, thus an approximation of their ages can be obtained. A caveat is that aeolianite exposures on much of the Cape coast exhibit extensive crossbedding and a lack of lateral persistence. Other than being able to conclude in broad terms that sites at the base of aeolianite cliffs are older than those towards the top of the cliffs, this limits the accuracy of any conclusions if sites are not directly dated. Paleosols, by way of contrast, may exhibit more lateral persistence (e.g., Roberts et al., Reference Roberts, Bateman, Murray-Wallace, Carr and Holmes2008) and may thus provide more accuracy in this regard.

At Site 1 an OSL age of 76 ± 5 ka was obtained ∼40 m to the north and from the same elevation Leic23004, (Helm et al., Reference Helm, Carr, Cawthra and De Vynck2024b). Although the burrow site and sampling site are from the same elevation, it cannot be assumed that they are from the same unit or layer.

At Site 2 the closest site dated using OSL (Leic21008) lies 6 km to the east, where an age of 134 ± 9 ka was obtained (Helm et al., Reference Helm, Carr, Cawthra, De Vynck, Dixon, Lockley and Stear2023d). The distance of 6 km unfortunately limits the usefulness of this result.

At Site 3 the closest site dated though our OSL dating project (Leic20024) lies 300 m to the west, where an age of 109 ± 9 ka was obtained (Helm et al., Reference Helm, Carr, Lockley, Cawthra, De Vynck, Dixon and Stear2023c), while an age range of 140 ± 8 ka to 91 ± 5 ka was previously obtained from a sampled section spanning the full thickness of the cliff exposure at a site 100 m to the west (Roberts et al., Reference Roberts, Bateman, Murray-Wallace, Carr and Holmes2008). The Site 3 paleosol containing the possible aardvark burrows is laterally persistent and appears to be the same as ‘P1’ in (Roberts et al. Reference Roberts, Bateman, Murray-Wallace, Carr and Holmes2008); the ages obtained therein from sediments above and below this layer (DF05/2/1, 2/2, and 2/3) allow some narrowing of this age range to circa 126–114 ka.

At Site 4 the closest dated site (Leic20025) lies 1.1 km to the east, where an age of 78 ± 5 ka was obtained (Helm et al., Reference Helm, Bamford, Carr, Cawthra, De Vynck, Dixon and Quick2023b). This is a typical result for this stretch of the Goukamma coastline. Finally, in the region of Site 5, the basal unit has been dated (Leic22025) through OSL to 126 ± 8 ka (van Tonder et al., Reference van Tonder, Cawthra, de Vynck, Quick and Ntsondwa2024), a period with a comparable climate and sea-level to the present.

As discussed above, the limitations imposed by the difficulties in aeolianite stratigraphic correlation and the distances of the OSL sampling sites from the purported burrow sites are acknowledged. Nonetheless, the results are consistent with others obtained from, for example, the Goukamma region and the area east of Still Bay, and more generally in terms of the dominance of MIS 5 ages that are reported for the seaward-most aeolianite deposits (Bateman et al., Reference Bateman, Carr, Dunajko, Holmes, Roberts, Mclaren and Bryant2011). Of these results, the age range estimate of circa 126–114 ka for Site 3 is regarded as the most reliable, given the stratigraphic inferences that can be made.

Review of the sites

The five burrow sites most likely span an age range from circa 134–76 ka, potentially representing MIS Stage 6 through 5a. During this time period, sea level would have varied from ∼110 m lower than the current mean sea level during the MIS 6–5e transition, to 6–8 m higher than the current mean sea level during the MIS 5e high-stand, to ∼45 m lower than the current mean sea level during MIS 5a (Spratt and Lisiecki, Reference Spratt and Lisiecki2016).

Burrow site 1, comprising three sub-circular or elliptical cavities from a single horizon, may represent part of an aardvark burrow complex seen in cross section with the preservation of short tunnels. The two tunnels that connect from the right cavity to the overlying surface may represent part of the burrow complex, although one of them is small. It can also be postulated that storm surges may have eroded this cavity and exploited lines of weakness at its distal end to create ‘blowholes.’ The raised feature close to the entrance of the middle cavity is intriguing. The presence of bedding planes within it makes it unlikely that it represents the remains of a mound of excavated material beside the burrow entrance. A more likely explanation is that it represents part of the infill from an extension of a burrow. The infilled trace (1 km to the north), 18 cm in diameter, is small for an aardvark burrow and large for a mole rat burrow and may represent a springhare burrow.

Burrow site 2, comprising two sub-circular cavities, is similar to Site 1, and may represent part of an aardvark burrow complex in cross section, with the preservation of short tunnels.

Burrow site 3, containing three circular or elliptical features in a paleosol, may also represent an aardvark burrow complex in cross section. In this case, each feature is infilled. The associated snail fossils are typical of regional paleosols from the Pleistocene.

Burrow site 4 provides an example of a burrow trace that is not evident only in cross section. The infilled burrow is essentially a natural cast, and the large sub-parallel ridges in the cast of the chamber wall may represent infilled claw scratch casts. The smaller, shallower sub-parallel ridges, separated by 2 cm, may also be claw scratch casts, but may have been registered by a juvenile aardvark or by a secondary modifier.

Burrow site 5 provides the most compelling evidence of an aardvark burrow, seen both in cross section with a sub-circular shape, and for some distance as a hollow burrow with sub-parallel claw scratch marks on the wall.

In summary, three of the sites are cavities and two sites are infilled burrows. At three sites more than one burrow feature is present, and at two sites only one burrow is present. In two cases claw scratch marks are present in the wall, highly likely at Site 5 as sub-parallel grooves, and more equivocally at Site 4 as sub-parallel ridges as part of a burrow cast. Two sites occur in paleosols (the other three occur in aeolianites) and one feature is interpreted as a chamber. Sites 4 and 5, with what we interpret as claw scratch marks, provide the strongest evidence. Sites 1, 2, and 3, presenting as tubular features (cavities and tunnels, or infilled) with a sub-circular appearance in cross section, suggest aardvark burrows but with less certainty.

The possible aardvark tracksite contains one relatively well-preserved track and an enigmatic feature containing linear elements that follow the same orientation as the well-preserved tridactyl track. The track bears a close resemblance to the tracks of modern aardvarks, but in the absence of a definite trackway attribution to an aardvark, the trackmaker attribution is tentative. If this is an aardvark track, and noting that the track is preserved in hyporelief, the outward convexity evident in two of the digit casts suggests that it was probably registered by a left hindfoot. If this interpretation is correct, it would be the first aardvark track in the global ichnology record.

Ichnotaxonomy

A comprehensive global summary on fossilized vertebrate burrows was provided by (Melchor and Cardonatto Reference Melchor, Cardonatto, Lucas, Klein and Huntin press). Aligning this with the findings described here allows for an enhanced perspective on the relevance of aardvark burrows in the global record, and the potential for assigning an ichnotaxon to aardvark burrows. Criteria established to aid in the identification of vertebrate burrows, and potentially for assignment to an ichnotaxon (Lucas et al., Reference Lucas, Gobetz, Odier, McCormick and Egan2006; Cardonatto and Melchor, Reference Cardonatto and Melchor2021), apart from being a sub-cylindrical structure of approximately uniform diameter, include (1) the overall burrow size (at least 3–5 cm in diameter), along with the architecture and morphology of the burrow system and the ramp inclination; (2) the presence/absence of chambers and their location and contents; (3) surface ornamentation, if present (e.g., near-parallel grooves in the wall or ridges on burrow casts, including the pattern, number, and dimensions of claw/tooth traces); (4) infill, if present, that often contrasts with the surrounding rock; (5) cutting through sedimentary structures, often at a low angle to what would have been the horizontal at the time of deposition; and (6) occurrence in a continental succession, and often in a paleosol.

(Melchor and Cardonatto Reference Melchor, Cardonatto, Lucas, Klein and Huntin press) indicated that there are 15 vertebrate-burrow ichnogenera and 23 vertebrate-burrow ichnospecies that are “available,” and 6 ichnogenera and 7 ichnospecies that are “unavailable,” (e.g., nomina dubia). The findings thus far identified at the five Cape coast sites, while allowing for an identification of fossilized aardvark burrows, do not yet meet the criteria for assignment to an existing ichnotaxon or the erection of a novel ichnotaxon. Indeed, (Melchor and Cardonatto Reference Melchor, Cardonatto, Lucas, Klein and Huntin press) rely heavily on neoichnology for an understanding of burrow morphology and characteristics, whereas paleoichnology should provide the criteria for such assignment. Comparison with the extensive documentation of armadillo burrows from the Americas (McDonough et al., Reference McDonough, DeLaney, Le, Blackmore and Loughry2000, and references therein) and the role of neoichnology (Cardonatto and Melchor, Reference Cardonatto and Melchor2023) may prove fruitful. The findings described herein are therefore regarded as preliminary in nature, pending further dedicated exploration of suitable deposits, and the features described are not yet assigned to an ichnotaxon. Likewise, aardvark tracks are distinctive, and identification of an unequivocal aardvark trackway would allow for the proposal of a new ichnotaxon.