All the World's Antelopes: Waterbuck and marsh-dwellers

Kob

One of the features of the reduncinine subfamily of antelopes, as opposed to most of the other groupings, is that they require ready access to standing water. Many of them, such as the reedbucks, are grassland animals, avoiding the driest areas, but otherwise living in plains and mountains, only retreating to riverbanks and marshes during the dry season. Others may, if anything, be even more tied to the water.

The kob (Kobus kob) lives across the savannah belt south of the Sahara, from Senegal to Uganda. It is said to never be seen more than 10 km (6 miles) from standing water, and usually much less. The unusually blunt scientific name comes from two different authors, with Charles Hamilton Smith having added the first half in 1840, after the animal had been originally described (as Antilope kob) by Erxleben much earlier, in 1777.

It's a moderately-sized antelope, standing between 85 and 100 cm (2'9" and 3'6") tall at the shoulder. The coat is golden to reddish-brown, with white underparts and white markings on the face. While all males become darker as they age, this is especially true in the easternmost subspecies, where they eventually become near-black, only retaining the white markings; there were proposals to split this off as a separate species in the early 2000s, but, absent clear genetic evidence, this is not widely accepted today. As with other reduncinines, only the males have horns, and these are lyre-shaped, reaching about 50 to 60 cm (20 to 24 inches) in length when fully grown.

It lives on grassy floodplains and other open habitat, avoiding forest, although it may retreat to lightly wooded areas in the dry season. When the rains come, the plains become lush with grass, and the kob feeds on little else, but at drier times of the year their diet is wider, with some studies suggesting about half of it comes from herbs and tree leaves. 

Kobs are only moderately social; they gather together in large herds of 50 individuals or more, but these do not seem to be permanent associations. Indeed, they are most commonly seen when either food is especially abundant at the start of the rainy season, or when access to water is limited during the dry; in between, they gather in much smaller groups, of perhaps no more than five each. There is also evidence that herd sizes have decreased over recent decades due to pressure from hunting, although the species is widespread enough and lives in sufficient protected areas that, as a whole, it is not considered to be threatened.

Their breeding habits may have changed over the same time frame. Adult males live apart from the females, in small bachelor herds when young, and then largely on their own once they are old enough to breed. The natural habit of kobs, historically, seems to have been "lekking" - the male defends a small patch of mating ground and attracts the females to it. As population densities have dropped however, it has become more viable for the males to defend larger territories, focussing more on deterring rivals from entering it than attracting mates who already live there. 

This has the advantage, from the male's point of view, that he can control access to the females, and be sure most calves are his. Where lekking still occurs, the female can simply wander from one patch to another nearby, mating with however many males she feels like - up to nine partners have been recorded within a close timeframe.

Such defence consists largely of posturing, with the traditional lekking behaviour often consisting of the male standing somewhere prominent such as the top of an anthill - something easily adapted to intimidating other males. While this seems sufficient in most cases, rare outbreaks of violence do occur, with the males clashing with their horns. Presumably they could have done the same when population densities were higher, and they must have done so on occasion, but the effort of fighting off too many nearby rivals may not have been worth the trouble.

Breeding occurs throughout the year, although births are more common around the start of the dry season. The pattern after birth is the same as that for other reduncinines. The infant remains concealed in long grass for the first six to eight weeks, being visited periodically by its mother for feeding. It is only after this that it begins to follow its mother around, socialising with other nearby animals.

Lechwe

In contrast, the lechwe (Kobus leche) is a true marsh-dweller. They live only in wetlands, spending much of their lives wading about in shallow water, although they will also utilise nearby lush grasslands. They prefer to have a good view of their surroundings, and so avoid woodlands, but their watery habitat also discourages lions from pursuing them. When this does happen, they bound through the water to escape, landing all four feet on the ground at once. While they prefer that the water they live in be no deeper than 50 cm (20 inches), they can also swim in deeper channels and will do so if they have to.

These habitat requirements inevitably mean that lechwe have a discontinuous population, split apart from one another by the vagaries of geography, since marshes are rarely that extensive. They are found primarily in Zambia, but with significant populations in Angola, Botswana, the DRC, and the Caprivi Strip of northeast Namibia. (Namibia is largely arid, but the Strip is much less so, since the whole point of it was to allow German traders access to the Zambezi). 

Lechwe seem to be pure grazers, eating little but long, lush marshland grass. Exactly which grasses they eat may vary throughout the year, as waters rise and recede with the seasons. In winter, they also eat sedges, but their restricted habitat seemingly gives them little opportunity to eat much else even if they wanted to.

They have a similar build to kobs, but are slightly larger, with the largest males reaching 115 cm (3' 9") at the shoulders, and typically have a redder coat. Perhaps the clearest distinction is in the horns, which are about the same length as in kobs, and have a similar ringed structure, but are straighter and splayed outwards rather than curving back. 

The herd structure is highly unstable, with membership of groups changing over the course of just a few hours. Nonetheless, lechwe can gather in immense herds at times, with hundreds or even thousands of individuals feeding in the same area. While most antelopes rest during the heat of the noonday sun, lechwe only do this during times of the year when the water level is low, apparently cooled enough by their partial immersion not to be concerned otherwise. There is some evidence that they may head onto drier neighbouring ground at night to graze there, but detailed studies are lacking.

Since population densities can be high in the limited areas where they live, male lechwe still stick to the lekking habits that kobs have largely abandoned since the 1980s. Males maintain small territories on the water's edge, from which they seek to attract mates from the surrounding marshland. Often, this means that they spend their time on small islands, which can potentially be very close to one another. Territories are typically about 0.06 km² (15 acres) and can be much smaller, with the actual lekking patch being no more than 10 metres (30 feet) across. If male intruders are not intimidated away by their mere presence, the defender can chase and fight them, pushing with locked horns.

There is a distinct breeding season, such that calves are born at the start of the dry season, just as the waters begin to recede and reveal stands of lush grass. Infants are hidden in stands of reeds, the marshy habitat being ideal for such concealment so long the ground is not too flooded.

Nile lechwe

As with kobs, and many other antelopes, there have been proposals to split the lechwe into multiple species. Today, however, only one of these distinct species is widely recognised: the Nile lechwe (Kobus megaceros). This lives around the White Nile and its tributaries in South Sudan and neighbouring parts of Ethiopia in habitats essentially the same as those of its southern relative. They are, however, reported to avoid areas with heavy growth of papyrus, presumably because these tall sedges obscure their view of any predators thinking about taking a dip.

Visibly, the Nile lechwe is clearly distinct from its southern cousin. Females are a drab ochre colour, lacking the rich red of the common species, but the males are much darker, with a thick shaggy coat that emphasises their already much larger size. Unlike the females, they have distinct white markings, likely to make them look attractive to potential mates. As the second half of their scientific name suggests, their horns are much larger than those of regular lechwe, having a more lyre-like shape and reaching up to 87 cm (34 inches). 

Their marshy habitat results in similarly large congregations as well, although there are some reports of a distinct social hierarchy among the females that seems less evident in the unstable grouping of the southern species. Males compete for access to the females, typically with brief bursts of violence, wrestling with their horns, and sometimes with each animal trying to hold the other's head underwater until it submits. That's normally effective, but in captivity, where the options for escape are limited, the dominant animal can be so enraged by the continued presence of its rival that the latter may die from its injuries.

On the other hand, dominant males ignore other males that have yet to develop the white markings on their face that come with full adulthood. Significantly, the development of this pattern seems to be delayed in subordinates living in captivity, which rapidly change colour if a larger male dies and leaves a vacancy.

Unfortunately, South Sudan is not a good place to live at the present, and that's as much true for antelopes as for humans. While expansion of farmland may be a risk to Nile lechwe, the larger one is probably poaching, both by illegal hunters in a country with limited countryside law enforcement and active predation by food-starved armed militias and their opponents in the official army. Should the current civil war come to an end, there are plans to construct a canal that would divert water to agricultural land to the north, which would be further bad news for the Nile lechwe, and other animals and plants relying on the local wetlands.

As a result, the Nile lechwe has been listed as an endangered species since 2008.

Waterbuck (female)

The same cannot be said for the waterbuck (Kobus ellipsiprymnus), which is one of Africa's most widespread antelopes. They are found across all of the savannah regions of the continent, across North Africa from Senegal to Ethiopia, and from there south all the way to South Africa. While not immune from hunting, any population decline is, so far, thought to be insufficient to pose any threat to the species.

They are larger than kobs or lechwe, with males standing up to 136 cm (4'6") at the shoulder and weighing up to 265 kg (580 lbs), although females are notably smaller. They have a shaggy, dark-grey coat smeared with an oily secretion that may help repel water, and various white markings, most notably a "bib" on the throat and a a ring pattern around the rump that may be used in social signalling. The horns lack the double curve seen in kobs and lechwe, curving out and upwards, and reaching 92 cm (36 inches) in length. 

They live in grasslands, much as kob do although, as the name suggests, they are also closely associated with water, rarely straying more than 1 or 2 km (roughly a mile) away. While they feed on grasses for much of the year, they will switch to a wider diet in the dry season, and the northern subspecies (although not, apparently, the southern one) regularly wades out into shallow water to graze on sedges or other water plants where they peak above the surface.

Females live in herds of up to 20 members, although more break up into smaller groups during the wet season. As with their relatives, however, membership of these herds is very fluid, varying from day to day to such an extent that there is no indication of any social hierarchy within them; it would probably be too much effort to establish one when you would have to reassert your dominance over newcomers several times a day. While adult males are solitary, younger ones live in bachelor herds of about five members, and these do seem to be stable, and moreover, to develop a dominance hierarchy even before they are old enough to breed.

As a result, females range over territories as large as 6.5 km² (2½ square miles), while males defend small patches of high-quality grassland of no more than 0.9 km² (220 acres). They do this by posing in such a way as to show off the length of their horns, resorting to violence only if an incoming male refuses to back down, as most do. There is, nonetheless, evidently competition for such prime areas, and only around 20% of males will ever get to hold a territory during their lifetime. At any given time, however, around 8% of males hang about on the edges of the territory of a more dominant counterpart, sharing in its defence while not competing for females, probably in the hope of getting to take it over in due course.

Puku

The puku (Kobus vardonii) lives in much the same region as the common lechwe, in Zambia, Angola, Botswana, the southern DRC, and parts of Malawi. While it, too, is reliant on water, it is not a true marsh-dweller, preferring to graze at the margins of wetlands rather than wading into them. This allows the two to live side by side without competing, given that they otherwise have very similar diets and general requirements. Equally, their diet is different from that of other antelopes living in the area (such as sable antelope), with the animal eating different grasses, perhaps because of their preference for not wandering far from water.

Puku are, marginally, the smallest of the species in their genus, with the largest males not exceeding 85 cm (2' 9") at the shoulder, and females rather smaller. Dominant males are said to have visibly muscular necks, something that must stand them in good stead while horn-wrestling. Both sexes are a golden-yellow colour, appearing very similar to the kob, but distinguished from it largely by the absence of black markings on the front of the legs.

While they have not been studied to the same extent as the other species, their behaviour seems largely similar. Herds only exceed 20 members during the dry season, when they huddle close together around remaining water sources, and males are either solitary or live in small bachelor herds. Females move about, but not across an especially large territory, while dominant males defend small patches of high-quality land, using a two-tone whistle to warn off would-be intruders as well as visual displays and, if necessary, aggression. Female puku often travel in mixed groups with impala, at least for short periods, sharing in mutual defence without competing for the same grasses.

That brings me to the end of the reduncinine antelopes, a relatively small subfamily in terms of number of species. The largest subfamily is that of the gazelles, which I have covered elsewhere, but the second largest is far less well-known, consisting, as it does, of mostly small and elusive species. It is to that that I will turn next.

[Photos by "flowcomm", Ian Restall, Tylwyth Eldar, Derek Keats, and Timothy Gonsalves. Cladogram adapted from Bibi, 2013.]