A new hypothesis for the steenbok (Raphicerus campestris) in the Highveld of South Africa: it was naturally absent

It is easy to assume that the steenbok (Raphicerus campestris) was indigenous to the Highveld (https://en.wikipedia.org/wiki/Highveld) when European explorers arrived.

However, I suggest that it was actually absent.

This would help to explain why its current taxonomic status in the Highveld is so nebulous (https://www.inaturalist.org/journal/milewski/70638-the-steenbok-raphicerus-campestris-in-the-highveld-a-simple-question-gone-impossibly-complex#).

My argument is based on an ecological rationale, but seems consistent with the historical record.

The steenbok tends to be taken for granted as widespread and ecologically tolerant. However, it is more ecologically specialised than first it seems, in diet and habitats.

This species is part of a guild of relatively small herbivores including

All eat both grasses and dicotyledonous plants, in various combinations according to the seasons (https://www.researchgate.net/publication/230164079_The_feeding_ecology_of_a_very_small_ruminant_the_steenbok_Raphicerus_campestris).

Because it has so many competitors, R. campestris may have been somewhat limited in occurrence in prehistoric South Africa, when the full fauna of the Holocene remained.

The Highveld contained by far the most complex fauna of ungulates of any region of treeless grassland on Earth (https://www.sciencedirect.com/science/article/pii/S0254629915003051 and https://www.researchgate.net/publication/282619832_Why_was_the_Highveld_treeless_Looking_laterally_to_the_Pampas_for_global_edaphic_principles_beyond_biogeographical_accidents). This may have precluded a niche for R. campestris under natural conditions.

I suspect that it was only when the fauna was disrupted by human settlement that R. campestris spontaneously entered the Highveld, from the west and north.

The idea is that it filled in for the species virtually exterminated by settlers, particularly the formerly abundant and migratory A. marsupialis.

This is not to claim that R. campestris became abundant in the Highveld, but merely that it became viable there because of, rather than despite, anthropogenic disturbance.

Three subspecies were thus hypothetically recruited to the Highveld, then mixing there through hybridisation. These are R. c. campestris (southwesterly origin), R. c. steinhardti (northwesterly origin), and R. c. capricornis (northeasterly origin).

Another basis for my hypothesis is habitat, particularly the natural availability of cover.

In its original state, the Highveld was treeless over extensive areas, partly owing to the intense natural herbivory. This hypothetically made the grassland too open for R. campestris.

There are two situations, in the Highveld today, with some shrubby indigenous cover, viz.

  • perennial drainage lines, and
  • scattered rocky outcrops.

However,

The settlement of the Highveld has boosted the incidence of woody plants, for various reasons.

I have before me du Plessis S F (1969, The Past and Present Geographical Distribution of the Perissodactyla and Artiodactyla in Southern Africa).

On page 100, du Plessis states for 'Orange Free State':
"Though no doubt occurring everywhere in this province in the past, practically no written records could be traced...Only Smith (Kirby, 1939) in 1835 mentions it as being common near the confluence of the Riet and Modder rivers".

This location (https://en.wikipedia.org/wiki/Riet_River) is actually west of Free State province and the Highveld, being located in the current Mokala National Park (https://en.wikipedia.org/wiki/Mokala_National_Park).

Much of the Highveld occurs in the former Transvaal (https://en.wikipedia.org/wiki/Transvaal_(province)). However, once again du Plessis (1969) largely draws a blank in the historical record.

The exceptions are as follows:

  • "Mauch (Petermann, 1870): north of Lydenburg"
  • "Holub (1881): near the Vaal River in western Transvaal"
  • "Holub (1890): between Bloemhof and Christiana"
  • "Baldwin (1894): the vicinity of Potchefstroom"
  • "Randall (1895): the open flats in the Barberton District."

The relevant locations mentioned are:

All of these are rather marginal to the Highveld, except for Potchefstroom. However, the latter is located in the valley of a major drainage line (https://en.wikipedia.org/wiki/Mooi_River_(Vaal)).

On page 103, du Plessis states the incidence, as of 1969, as follows:
"Orange Free State: Van Ee (1962): fairly generally distributed throughout the province with the greatest numbers along the rivers and in the mountainous districts of the east, especially in the Fouriesburg, Tweeling, Petrus Steyn, Boshoff, Theunissen, Brandfort, Hoopstad and Koffiefontein districts. Roberts (1963): 45 in the Willem Pretorius Game Reserve".

The status in Transvaal (page 104) was similarly widespread, as of 1969.

So, dear readers, please prove me wrong in my suggestion that the steenbok was naturally absent from the Highveld, including virtually the whole of what is now Free State.

One way to do so might be to consult a work to which I currently lack access. This is by Skead (https://en.wikipedia.org/wiki/CJ_Skead), covering that part of the Highveld falling within the Eastern Cape (https://ace.mandela.ac.za/Historical-Incidence-of-the-Larger-Mammals/Authors/The-works-of-Cuthbert-John-(Jack)-Skead),

In the meantime, the following is a compendium of all the current photos of R. campestris, located in the Highveld, in iNaturalist:

https://www.inaturalist.org/observations/129166689
https://www.inaturalist.org/observations/105216875
https://www.inaturalist.org/observations/108317173
https://www.inaturalist.org/observations/69266940
https://www.inaturalist.org/observations/127743228
https://www.inaturalist.org/observations/127670769
https://www.inaturalist.org/observations/98953074
https://www.inaturalist.org/observations/130857789

Only four of the above observations show the animals clearly.

Also see https://www.inaturalist.org/journal/milewski/70638-the-steenbok-raphicerus-campestris-in-the-highveld-a-simple-question-gone-impossibly-complex#.

Posted by milewski milewski, 01 October, 2022 06:54

Comments

if you go to https://www.inaturalist.org/taxa/42375-Raphicerus-campestris
in the layers box, switch off checklist-places and range and switch on GBIF-network
The relative museum data for different areas is apparent.

Posted by tonyrebelo 2 months ago (Flag)
Posted by tonyrebelo 2 months ago (Flag)

@tonyrebelo

Many thanks for this.

When I view the GBIF records, there are a few additional locations in the Highveld.

However, the main change is that there is an astonishing number and spread of records in southern and southwestern Angola.

This is so surprising to me that it seems like a metaphorical 'tip of the iceberg'.

Could it possibly be true that the Portuguese did such thorough collection in Angola?

And could it possibly be true that such a vast range of the steenbok is unappreciated today (presumably the species is still extant there, in full mumbers)?

If the Angolan specimens are ssp. steinhardti, then this would make steinhardti the most widespread of the sspp.

What is particularly astonishing is the difference between Angola and Zimbabwe.

The 'range extension' revealed in Angola is so vast that it is bigger than the whole country of Zimbabwe.

Furthermore, the density of records in Angola, vs the sparsity of records in Zimbabwe, is astonishing (particularly because the steenbok ostensibly penetrates the miombo biome near Sa da Bandeira in southwestern Angola).

Posted by milewski 2 months ago (Flag)

@tonyrebelo @jakob

The subspecies name 'natalensis' is often cited for the steenbok, with an implication that the species was originally recorded in or adjacent to the Highveld (explicitly 'Drakensberg and highveld of Southern Transvaal', bottom of page 341, Roberts, 1951).

However, having read the details in Roberts (1951), I think this notion (and name) should be discarded.

The location given by Rothschild (1907) for the specimen of natalensis was 'Drakensberg, Natal'. This already seems both unlikely at a regional scale, and too vague to have any taxonomic validity anyway.

The description indicates extreme darkness, exceeding even that typical of the nominate form of the southwestern Cape. This again sounds most unlikely for the location claimed.

This specimen was probably collected near Cape Town, and then irretrievably mislabelled and thus mislocated.

Roberts (1951, page 341) himself comments "this is an inadequate and misleading description...the matter must remain in abeyance until more material is compared, as the distribution seems extraordinary".

My conclusion:

There is no such thing as natalensis, because there is no valid provenance for any specimen, no evidence that the species has ever occurred.in the region claimed, and no credibility in the description w.r.t. the alleged location

This misinformation has steered us in the wrong direction for more than a century. We should disregard 'natalensis' and the whole notion that the steenbok has anything to do with the Drakensberg.

The steenbok has been, and remains, absent from the Drakensberg and the associated treeless grasslands of the whole belt, east of the escarpment, from Eastern Cape through Natal to Mpumalanga. My hypothesis, that the steenbok was actually absent from the Highveld in general, merely extends this biogeographical pattern of natural absence in a westerly and northerly direction.

Posted by milewski 2 months ago (Flag)

If I am right, the natural distribution of the steenbok in South Africa was largely mutually exclusive with that of the black wildebeest, Connochaetes gnou (https://www.ewt.org.za/wp-content/uploads/2019/02/5.-Black-Wildebeest-Connochaetes-gnou_LC.pdf).

Posted by milewski 2 months ago (Flag)

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