Antilopine Antelopes: Dwarf Antelopes of southern Africa

Steenbok

The "antilopine" subfamily of antelopes, so named because it happens to include the first animal scientifically described as an antelope rather than a goat, is itself divided into at least two major branches. There may or may not also be minor ones, depending on what you think is worthy of naming, but the two main ones are quite clear, and perhaps separated from one another around 12 million years ago towards the end of the Middle Miocene.

One of these groups contains the gazelles, along with the springbok, some other gazelle-like animals, and that "first" antelope mentioned above, the blackbuck. These are, for the most part, smallish slender, fast-running antelopes living in arid or semi-arid habitats in both Africa and Asia. The second group are the dwarf antelopes, found only in Africa and quite visibly different from gazelles. 

That's not least, of course, because they are smaller. There are, in fact, other antelopes of similar size, but nonetheless, these are the 'true' dwarf antelopes, significantly smaller than the majority of such animals. Compared with gazelles, they are probably less well-known to the public, and have generally not been studied as thoroughly by scientists either, despite being relatively common animals where they live.

The steenbok (Raphicerus campestris) is a typical example. Unusually, this lives in two distinct areas, separated by a gap of around 800 km (500 miles). The larger area covers pretty much the whole of southern Africa, from southern Angola and southern Mozambique in the north down to the Cape, taking in Zimbabwe, Botswana, South Africa, Eswatini, and parts of Zambia on the way. The other covers much of Kenya and Tanzania.

Steenboks stand between 45 and 60 cm (1½ to 2 feet) high at the shoulder, and weigh from 9 to 13 kg (20 to 30 lbs), with little difference between the two sexes. They have large ears, and the male has horns that form vertical spikes around 12 cm (5 inches) in length; these are mostly smooth, but with some rings near the base. The scent glands in front of the eyes are smaller than in many gazelles, but still present, while there are apparently no anal glands. There is also an additional scent gland under the chin that is typically not seen in antelopes. Steenbok are brownish in colour, with pale undersides and few other markings.

The word "steenbok" is, as one might imagine, Afrikaans. It's derived from the Dutch word for ibex, and literally translates as "stone buck", something that arguably makes more sense for the species of goat than it does the antelope. Far from living in mountains, as ibex do, steenboks are primarily plains-dwelling animals, although they can venture into hills or highland plateaus up to 3,500 metres (11,500 feet) above sea level.

Their primary habitat is grassland or scrubby bush, and they tend to avoid more wooded areas. It's notable, for instance, that the large gap between their two ranges is occupied primarily by subtropical miombo woodland. Climate change at the end of the Ice Ages may have made this region unsuitable for the animals; although the steenboks on either side are considered to represent different subspecies, there are apparently no reliable ways of telling them apart. 

Since they spend so much time in grassland, it had long been assumed that they must eat a lot of grass. In fact, at most times of the year, it's a relatively minor component of their diet. Instead, they eat a mixture of herbs and bushes, including the leaves of woody plants such as bushweed, although they have also been observed scraping at the ground to get at roots and tubers. In Nambia, the driest part of their range, they eat a higher proportion of succulent plants, sufficiently so that they do not need to drink open water, perhaps helped by a low metabolic rate.

Steenbok are not regarded as herd animals, instead living in mated pairs. How long a given pair stays together is unknown, and while they inhabit the same general area, they don't seem to spend that much time in each other's company, fleeing in opposite directions if startled. How large that area is varies significantly depending on the quality of the land; it has been recorded as anything from 4 hectares to 1 km² (10 to 1,000 acres). They mark this territory by using dung piles, scraping the ground around them with their feet to use the scent glands between their hooves. The secretions of the glands in front of their eyes are complex and likely used to scent-mark on low-lying plants.

Breeding takes place throughout the year, with females able to give birth about once every eight months or so, once their previous calf has been weaned. Courtship consists of the male following the female about, licking her genitals and gently kicking her hindlegs (the latter ritual, called laufschlag, is common in many hoofed animals, including gazelles). As is common with antelopes, the young calf is initially hidden in tall grasses until it can move about safely by itself.

Cape grysbok (male)

The steenbok was given its scientific name by Swedish naturalist Carl Thunberg, a student of Linnaeus who had lived in what was then the Cape Colony for three years in the 1770s while working for the Dutch East India Company. The colonists at the time distinguished three different kinds of small antelope: the steenbok, bleekbok, and grysbok. The bleekbok ("pale buck") is now known to be just another name for the steenbok, but Thunberg correctly identified the animal we now call the Cape grysbok (Raphicerus melanotis) as distinct, naming it in the same 1811 publication.

Although locally common (it probably helps that it isn't widely hunted) the Cape grysbok is found only along the southern coast of South Africa. It is less likely to inhabit grasslands than its close relative, preferring the dense thickets of bushes in the fynbos shrublands, although it does extend to nearby hilly or grassy areas if they have sufficient vegetation cover. 

Despite the name, the Cape grysbok is not notably greyer than its relative, although the hair is grizzled, which may account for the name. It's also much the same size, with a similar physique; the horns are slightly shorter at 8 cm (3 inches) and the preorbital scent glands are larger, forming distinct black spots in front of the eyes. As in steenboks, the hairless patch of black skin at the tip of the nose is unusually large, extending back in a short stripe along the front part of the snout.

They are browsers, but the exact composition of their diet is flexible, allowing them to switch from one food source to another if that becomes more available - something that can be bad news for farmers if they happen to live near plantations or vineyards. They are solitary animals, inhabiting much smaller home ranges than the steenbok, although they may share dung piles with neighbours. Males defend tiny territories of just 0.25 hectares (0.6 acres); if a potential rival approaches they do not bother with threat displays but simply stab them with their horns straight away. 

When steenbok are threatened by predators they run in a zig-zag pattern, interspersed with leaping into the air, although they lack the white underside to the tail that gazelles use to alert their fellows. Grysbok, on the other hand, take the simpler approach of just running away as fast as they can in a straight line, holding their head low and not wasting any effort on leaping. While steenbok are active both during the day and on moonlit nights, grysbok are primarily nocturnal.

Sharpe's grysbok (female)

For most of the 19th century, grysbok were thought to be widespread across southern and eastern Africa, but in 1897, British zoologist Oldfield Thomas split the animals into two species, which are still recognised as distinct today. The other is Sharpe's grysbok (Raphicerus sharpei), named for the collector of the first scientific specimen. Genetic evidence has recently shown that it is, in fact, more closely related to the steenbok than to the Cape grysbok, although there doesn't seem to be any move to change its common name accordingly.

Although similar in size and colouration, there are some distinct differences between the two grysbok species. Sharpe's grysbok has paler underparts, closer to white than the pale yellow-buff of the Cape species, and extending onto the underside of the tail. The ears have less hair and some black colouration around the edges, while the preorbital glands are smaller but deeper, and the horns of full-grown males are noticeably shorter. Most significantly, however, Sharpe's grysbok does not have the short "declaw" hooves seen above and behind the true hooves in most cloven-footed mammals and that, while they do not normally reach the ground can help to steady the animal on uneven terrain.

They live from southern Tanzania to far northeastern South Africa and Eswatini, taking in most or all of Mozambique, Malawi, Zambia, and Zimbabwe along the way. This, you may note, is almost exactly the same area that the steenbok doesn't live - although the two species do overlap at either end. The reason for this is that Sharpe's grysbok prefers miombo woodland, inhabiting woodland savannah regions with thick undergrowth, although it can also be found in heavily vegetated subtropical bushveld. 

There are, however, at least six other species of dwarf antelope spread across southern and eastern Africa. Next time, I will be heading north to look at those which most closely resemble the steenboks and grysboks.

[Photos by Bernard DuPont (1 and 3) and Ryan van Huyssteen (2), from Wikimedia Commons.]