All the World's Antelopes: Reedbuck and Rhebok

Bohor reedbuck

Quite where, within the larger bovid family, the reedbucks belong was long a matter of contention. They are medium-sized antelopes, tending to prefer habitats with plenty of water, distinguished by the fact that not only their visible horns, but also the bony cores on the inside, have transverse ridges running round them. The detailed structure of their teeth has some resemblance to that of the true bovines (that is, cows, bison, and the like) but it's hard to see that as anything other than parallel evolution. 

The most widely followed scheme in the late 20th century placed them with the grazing antelopes, such as sables and their kin, but even then there was a suspicion that this was only because nobody knew what else to do with them. Once we were able to do detailed genetic analysis, it turned out that they are pretty much in a group of their own, not especially close to anything, having diverged from the ancestors of the true grazing antelopes before that group diverged from the goats. Our best guess is that this happened between 16 and 14 million years ago; there are antelopes with longer lineages, but not many.

The first species of reedbuck to be described was the one for which the entire subfamily, the Reduncinae, was subsequently named. Its most common name today is the Bohor reedbuck (Redunca redunca), although many others are also used, even if we only count the English ones. When Pallas first described it in 1767, he said that it lived in what would now be Senegal, but it's much more widespread than that - which goes some way to explaining the multiple different names. 

In fact, it's found along a wide belt of land south of the Sahel, from the Atlantic coast in Senegal, Gambia, and Guinea, across all the way to central Ethiopia, and then southward through the East African savannah as far as southern Tanzania. At least five different subspecies have been identified across this wide range; it has been proposed in the past that four of these should be considered distinct species, but the modern consensus is that there is no strong evidence for this. (Which, in fairness, doesn't mean it's not true, just that we have no reason to suspect it is).

The bohor reedbuck stands between about 65 and 85 cm (2'2" and 3'9") in height, with males larger than females. The coat is a fawnish yellow, with clear white underparts and, in some subspecies, black markings on the front of the legs. Their hair has been described as "greasy", due to an unusually large number of sebaceous glands, secreting a lubricating and water-repelling oil. Like other reedbucks, only the males have horns. These are curved, with distinct ridges that are especially large towards the base; in the largest individuals, they can be as much as 40 cm (16 inches) in length. 

They are grassland animals, actively avoiding forests and woodland. It does, however, require nearby surface water, so it rarely ventures too far from rivers or other sources, and often moves into marshlands during the dry season. For the most part, this means that Bohor reedbucks are found in lowland areas, they can be found in some mountainous regions as high as 3750 metres (12,300 feet).

As one might expect for a grassland antelope, they are very much grazing animals, with at least 90% of their diet consisting of grass. They are active both day and night, grazing in areas of short grass for four bouts a day, but retreating into areas of much longer grass to escape the heat of the noonday sun. Here, they can lie down and allow the plant life to conceal them, doubtless aided by their coat being roughly the colour of dried grass. They can travel up to 6 km (3½ miles) a day, but don't usually bother unless they are having difficulty finding good places to graze.

They are not particularly sociable animals. While large aggregations can be seen around riverbanks or marshy areas where food is particularly plentiful, herds rarely number more than five individuals, and around half the females and almost all the adult males live alone. Each male defends a territory with an area of 20 to 30 hectares (50 to 75 acres) but, unlike many other species, they don't seem to actively mark its boundary, instead warning off potential rivals with a whistling call.

Males gather a sort of loose harem of up to five females, but this isn't the sort of grouping we'd normally think of since the females don't often stay close to each other, let alone the buck. There does not seem to be any particular breeding season, although it's possible that mating is less likely when young would be born at the height of the dry season. The male entices receptive females with a noise that is said to sound like a toy trumpet, as well as the usual flehmen gestures seen in many hooved animals. 

Females give birth to a female calf, but due to there being only limited studies on the species, and mothers being rather good at hiding their children, we know little about their development. We do know that territorial males will drive away any young males as soon as they start to grow horns; these often end up in bachelor areas that nobody else wants, in between the more preferable territories, at least until they become old enough to set up their own.

Southern reedbuck

The southern reedbuck (Redunca arundinum) lives, as one might expect, further south, although there is some overlap in Tanzania. It is found across the savannah belt of southern Africa, from Angola in the west to Mozambique in the east, extending as far south as northeastern South Africa and into the southern reaches of the DRC in the north. As with the Bohor reedbuck, there was a move to split it into two species in the 2010s, but this didn't come to anything.

Although there is considerable overlap, the southern reedbuck can reach significantly greater sizes than its northern relative, with some males apparently having a shoulder height as great as 150 cm (4' 11"). They otherwise look much the same, but with a drabber tone, and with black markings on the forelegs being more common, and sometimes present on the hind legs as well. Like the Bohor reedbuck, they have a glandular area beneath the ears that is covered by hair, but that becomes visible as a black patch when it is secreting (for a purpose that remains unclear).

They live in grasslands, with the vast majority of their diet consisting of grass, but they are more willing to venture into woodlands than their northern kin, being more of a savannah animal than a true grassland one. They require fresh standing water and retreat to riverbanks during the dry season, when they are also more likely to resort to eating herbs due to a lack of fresh grass. They are also willing to wade into water to feed, although they prefer to avoid anything deeper than about 20 cm (8 inches), so they're hardly aquatic.

Like the Bohor reedbuck, they are unusually antisocial for a "herd" animal. Even when they are seen gathering into groups, the membership of these groups is constantly changing, with no fidelity to their partners. Aside from females with their young - which stay together for almost a year - this means that, socially speaking, they are mostly solitary, even if they tolerate one another's presence and happily feed together. Males become territorial only around the breeding season, when they drive away rivals, although the exact way that this is arranged seems to vary between populations, probably based on how many reedbuck a given area can easily support.

There has been more research into the reproductive habits of the southern reedbuck than its northern counterpart, primarily in South Africa. As a result, we can say that infants remain hidden for the first six weeks of life, pressing themselves close to the ground in long grass. The mother stays within 200 metres (yards) but only visits once a day, usually at around noon, to provide milk, after which the fawn moves to a different spot, never reusing the same one twice. This is all to conceal the infant from predators, but should it fail, the mother is highly protective and aggressive, having been seen fighting off baboons.

Mountain reedbuck

The mountain reedbuck (Redunca fulvorufula) is of similar size to the Bohor species, but is grey in colour over most of the body, with a distinct reddish tinge to the hair on the head and neck. The glandular patch beneath the ears is hairless, and thus more regularly visible.

It is unusual in that it lives in three completely different parts of Africa, with no connection between them. There is no clear indication of how this could have happened, but it does make the suggestion that there are three different species at least a little more plausible than with the others. But then again, not necessarily, since it has been suggested that they once occupied a much wider area, before being split into three as a result of human activity.

One population lives in eastern South Africa, Lesotho, and Eswatini. A second lives in the northern part of the Great Rift Valley in Ethiopia and Kenya, with some extension into neighbouring countries, while the third, and by far the smallest, lives way over in the west, on the border between Nigeria and Cameroon.

What these areas have in common is, as one might expect from the common name of the antelope, mountains. Unlike the other species of reedbuck, they avoid flat terrain and lowland areas, never venturing below about 1,500 metres (4,900 feet) and often living twice that high up. While they do like grasslands, in their case these are montane grasslands, with steep slopes and rocky landscapes where most other hooved mammals will not venture (there being no goats in this part of the world), and predators are hopefully unable to pursue them.

Diet, habits, and social organisation are all broadly similar to the other reedbucks. Females travel in groups of up to eight, but don't stick with any particular group for long, apparently seeking safety in numbers rather than forming any long-term bonds with their fellow travellers. Males are solitary, picking territories on steep terrain where females are more likely to visit, their boundaries often marked by physical features. Although the glands under their ears are more visible than in the other species, they, too, do not use them for marking their territory, warning off rivals with whistling calls and, if necessary, aggressive posturing.

Since 2017, the mountain reedbuck has been considered an endangered species. This is not because they are especially rare - although they certainly aren't common - but a result of research showing that the South African population crashed by as much as two-thirds in the first 15 years or so of the 21st century. If that were to continue, it would obviously not be sustainable, and the two northern populations are much smaller, representing only 10% of the total between them. While trophy hunting may be a part of this, it's more likely that the expansion of agriculture and cattle ranching in the region has played the largest role.

Rhebok

The reedbucks are, however, not the only members of their small subfamily. One of the others is the rhebok (Pelea capreolus), sometimes called the "grey rhebok", despite the fact that they don't come in any other colour. The similarity in the name is a coincidence, since "rhebok" was originally a misspelling of the Dutch word "reebok", which means "male roe deer". (It was this latter spelling that influenced the sportswear brand, apparently because they came across it in a South African dictionary). Presumably, they reminded early European settlers of the animal from their homeland.

Rhebok live in the coastal and highland regions of South Africa and Lesotho, but not the arid interior. They are about the same size as reedbucks, with relatively thick grey hair and only a few faint markings. The horns, present only in the males, are straight and narrow, with the rings restricted to the base. Distinctive features include a comparatively large and bulbous rhinarium (the hairless, black bit on the end of the nose) and long, narrow, almost rabbit-like ears.

Although they can be found at low elevation in some coastal areas, for the most part, rhebok inhabit hilly or mountainous terrain. They prefer areas of open woodland, often just below the treeline, and avoid both dense forest and tall grassland. Together with their liking for steep slopes, this indicates that they are far more concerned about being able to see predators coming than they are about the possibility that the predator will also see them - something that makes sense if you're good at rapidly fleeing into inaccessible areas. (In contrast, reedbucks just duck down and hope not to be noticed).

It is also not regularly associated with standing water, as all other members of the subfamily are. The presumption is that, when this part of Africa began to dry out in the Late Miocene, all of the other species retreated to the few remaining places with a good water supply, while the ancestors of the rhebok took the opposite approach and evolved to do without.

It was long thought that the rhebok, like true reedbucks, was a grazer, but when scientists finally got around to analysing their dung, they got something of a surprise. Rhebok eat relatively little grass, with some studies showing that over 95% of their diet consists of leaves from shrubs and other low-lying, but non-grassy, plants. Paper daisies and Aspalathus legumes seem to be their favoured foods, although the details may vary across their range, depending on what is available.

Like true reedbucks, they are active both day and night, but they show less of an aversion to the noonday sun, possibly because many of them live at cooler altitudes. Similarly, when they do rest, it isn't in long grass, but in areas with a good view of the surrounding countryside.

Their social organisation is also quite different. Rhebok live in harem groups, with a single male, up to five adult females, and however many young and subadults may still be travelling with them. It is only those adult males who have yet to secure a harem that live on their own. Each of these herds occupies a distinct territory, typically around 65 hectares (160 acres), which the male marks with his dung, driving off any potential rivals. When travelling, however, he is at the back, with a female leading the way, so it is she who decides where to feed.

There is a distinct breeding season, but when it happens depends on which half of South Africa the animal lives in, something that has been attributed to the differing seasonal rainfall patterns across the country. Females treat their infants in much the same way as reedbuck mothers, the first few weeks after birth being the only time in a rhebok's life when it actually will try to hide in long grass or other dense vegetation.

The rhebok is unusual amongst the reduncine antelopes, sufficiently so that it is sometimes placed in a separate tribe within the main grouping. There are, however, five other species in the subfamily and next time, I will look at those.

[Photos by Yathin S. Krishnappa, Nathan Earley, Diego Rubolini, and Bernard duPont, from Wikimedia Commons.]