Module # 1 – Component # 4 Steenbok

WildlifeCampus – The Behaviour Guide to Mammals of the RSA Lowveld 1

Module # 1 – Component # 4

Steenbok

Raphicerus campestris

TRAITS.

A small reddish antelope with big round ears, rudimentary tail, slender build with long legs and well developed hindquarters.

Height and weight : 50 cm (45-60 Kg); males 10.9 kg, females 11.3 kg (9.7 - 13.2) (Botswana population).

Horns: sharp upstanding spikes 9 - 19 cm, ringed only at base. No false hooves; bare muffle, smooth, glossy coat

Coloration :Geographically variable: Bright rufous (East Africa) to rufous-fawn and rufous-brown; underparts, under-tail, and inside ears white; triangular black marking on nose, dark crescent on crown, and dark- fringed ears; sexes alike, newborn same colour but woollier coat.

Scent glands: smallish preorbital glands, larger in male; pedal glands in all feet, no inguinal glands, and possibly a throat gland.

Mammae: 4

DISTRIBUTION

Like the dik-diks and various other arid zone mammals, the steenbok has a disjunct distribution on either side of the Miombo Woodland Zone. It was formerly found to the Uganda and Somali borders, but Mount Kenya is now the northern limit of its range. In southern Africa it is common in suitable habitat practically everywhere south of the Zambezi and southern Angola, including the Kalahari but only along major rivers in the Namib Desert.

Steenbok © WildlifeCampus WildlifeCampus – The Behaviour Guide to Mammals of the RSA Lowveld 2

RELATIVES

The two grysboks, Raphicerus sharpel and R. melanotis, are enough alike to be considered a super-species and are geographically isolated. The Cape grysbok has a very restricted distribution at the tip of South Africa, and Sharpe's grysbok replaces the steenbok in the Miombo Zone. The steenbok's range overlaps that of both grysboks, notably in most of Zimbabwe, but the grysboks frequent much denser bush and appear to be mainly nocturnal. Accordingly a steenbok is more likely to be seen on the same ground, and to be confused with, an oribi than with a grysbok. A grysbok is somewhat smaller and quite different in appearance and movements from the steenbok: it has more rounded, higher hindquarters, shorter legs, a darker coat sprinkled with white hair, and moves in a crouch. Male grysboks also have a preputial gland, which the steenbok lacks.

ECOLOGY

For a small antelope that depends on cover for safety, the steenbok inhabits surprisingly open country, including grasslands dotted with bush and light woodland, from sea level up to 4750 m. However, it is more frequently associated with open plains in the Southern Savanna, where it overlaps with Sharpe's grysbok, than north of the Miombo Zone where it does not. In Kenya it is also common in denser cover, e.g. on stony, well-wooded hills and in acacia groves. The steenbok benefits from destruction of woodland, whether by man or beast, as colonising and regenerating vegetation creates ideal cover and browse for it. This antelope is thus associated with transitional and unstable conditions, especially in areas of low rainfall.

DIET

The steenbok is a concentrate selector that feeds on the leaves and shoots of a wide variety of low shrubs and trees, on forbs, seeds and seed pods, berries and fruits, and grasses in a young and tender stage. It also digs for roots and tubers in the Kalahari.

In a Kenya sample of 21 stomachs, the proportion of grass rose to as much as two thirds after rain or fire stimulated new growth, and in Botswana the contents of 25 stomachs were divided equally between browse and grass. But in Zimbabwe grass amounted to less than 30% (N = 91). The simple anatomy of the digestive tract makes it extremely unlikely that the steenbok could exist for long on roughage alone (ruminant digestion is discussed in Module # 2, Component # 1).

The steenbok is water-independent but has been known to drink when the opportunity arises.

Steenbok © WildlifeCampus WildlifeCampus – The Behaviour Guide to Mammals of the RSA Lowveld 3

SOCIAL ORGANIZATION

Territorial, monogamous pairs

No comprehensive study of the steenbok has been published. Although seen more often singly than in pairs, it seems probable that this species is distributed in couples which share the same territory but hide, rest, and forage separately most of the time, unlike the dik-diks or klipspringer but much like the gray duiker, for instance.

Perhaps the openness and size of steenbok territories, in which cover is typically patchy with intervening open terrain, make it safer for family members to remain dispersed rather than clustered. Even when encountered in pairs, the male and female typically flee in opposite directions. Estimates of home range/territory size vary from as little as 4 - 5 ha up to 1 km2. The latter estimate was based on observations of steenboks living in the Kenya highlands in comparatively open grassland. There, in 8 out of 10 sightings, a male and female were seen within 200 - 300 m of each other. There are no records of a male associating with more than one adult female. Indeed, a captive male placed with two females mated with only one and fought the other. The mated pair sometimes rubbed or nibbled one another's faces. Reports that both sexes participate in maintaining dung middens, if substantiated, would be further evidence that steenboks live in couples (but see under Territorial Behaviour).

Some published sex-ratio data for steenboks suggest a preponderance of males, notably in Kruger N.P., where 40 males and only 9 females were seen along the main tourist routes over a three-year period; and foetuses collected in a Zimbabwean tsetse control area suggested that even the natal sex ratio might be skewed toward males.

However, sizeable samples in Natal and Namibia yielded the even adult sex ratio expected in monogamous species, and tests of most other samples indicate no significant difference from a 1:1 ratio. Males, being more territorial and less timid than females, may well be seen more often along roadsides.

ACTIVITY

The steenbok is known to be active at night. In Matapos N.P. pairs often came out then to feed on lawns of short grass. Steenboks living in settled areas may become very largely nocturnal, but otherwise they are also day-active, with the usual early-morning and late-afternoon peaks, and may move about and feed at all hours on cool, overcast days. When lying up they apparently use regular resting places, preferably in cover.

Steenbok © WildlifeCampus WildlifeCampus – The Behaviour Guide to Mammals of the RSA Lowveld 4

POSTURES AND LOCOMOTION

A steenbok flushed from hiding dashes off suddenly at great speed on the usual zigzag course, making great bounds every few strides, with its outstretched head at or slightly below shoulder level. After reaching another patch of cover, it drops from sight. Grysboks carry the head lower and dash straight into cover without bounding.

SOCIAL BEHAVIOUR: COMMUNICATION

Largely unstudied. The relative importance of olfactory, vocal, and visual signals has yet to be determined. The fact that the steenbok lives in relatively open habitats and has contrasting white markings (especially eye ring, ear lining, and rump patch) indicates that visual communication may be more important in this antelope than in, for instance, the grysboks.

TERRITORIAL BEHAVIOR

Both sexes deposit dung on middens that may serve as territorial boundary markers. The performance resembles that of dik-diks but differs in detail: reportedly both sexes scrape the ground, not only before but also in between and after urinating and defecating. Moreover, steenboks sometimes scrape with the hindfeet after defecating. But a male I watched first scraped with his forefeet, straddled and urinated, scraped again, squatted and defecated on the same spot, then scraped again, never using his hind feet.

Numerous sandy little piles showed the locations of other recent deposits. Though he was accompanying and courting a female at the time, she did not participate in the ceremony. Because couples often live separated, Walther says the female establishes her own dung middens. The suggestion that covering the excrement would help retard drying and thereby prolong the scent in arid climates raises the question of why dik-diks leave theirs uncovered. Neither sex has been seen marking with the preorbital glands.

AGONISTIC BEHAVIOUR

Threat and dominance displays remain undescribed, except for the use of an erect posture in courtship (see below).

Fighting

A penned male became so aggressive when his mate came into oestrus that he attacked all intruders, human or animal, running alongside and stabbing at them with sideward head jerks. Since the steenbok's upright, sharp horns are as dangerous as the oribi's, it would be interesting to know whether it also engages in air-cushion fights and counter-chasing, thereby avoiding horn contact (see oribi account: Component # 6 of this Module).

REPRODUCTION

Reproductive tracts of 188 female steenbok shot on tsetse control in the Zimbabwe Lowveld indicated that ovulation occurred year round, with a possible birth peak early in the rains (November-December). Similar non-seasonal breeding was shown by 109 grysbok shot in the same area. Testes weights of adult males showed no seasonal variation and epididymal smears indicated that spermatogenesis continues through the year. Captive males can mate at 8 ½ months, when they are adolescent but still immature. Captive females have conceived at 6 - 7 (up to 9½) months, may calve at 1 year of age, and reproduce at intervals of about eight months. Gestation is estimated at 166 - 177 days.

SEXUAL BEHAVIOUR

Close following, genital-licking, lowstretch, foreleg-lifting, erect posture.

Courtship features the usual close following in lowstretch, genital licking and nudging, with frequent foreleg-lifting during which the female's hindlegs are often contacted (author's observations). Rubbing faces together and/or mutual facial nibbling may coincide with oestrus.

PARENT/OFFSPRING BEHAVIOR

A captive female dropped a calf ½ an hour after the amniotic sac became visible, while lying down. The fawn (weighing 1 kg) was up and nursing within 5 minutes (surprisingly quickly). At 2 weeks it began nibbling plants; the mother stopped lactating after 3 months. Calves remain concealed until well grown before beginning to accompany the mother, sheltering in tall grass or shrubs and lying prone with ears flattened to the neck, which is also the practice of hiding adults. Fawns have been reported to hide in abandoned holes, but this is unlikely to be a habit.

ANTIPREDATOR BEHAVIOR:

Close concealment; dodging run; alarm snorts.

The young are vulnerable to all predators down to the size of eagles and adults have to contend with carnivores as small as caracals, and possibly even jackals. They place primary reliance on concealment, lying prone in cover until discovery is imminent, then dash away at high speed to disappear in another patch of cover. Sudden flight may startle and thereby delay a predator. The steenbok can also change direction abruptly, a good tactic against the cheetah, for instance, and may have more endurance than most small antelopes.

SOURCES

Ansell 1964, Bigalke 1963a, Cade 1966, Chalmers 1963, Hofmann 1973, Hofmeyer and Skinner 1969, Keer and Wilson 1967, Kingdon 1982, Mentis 1970, Pocock 1918, Shortridge 1934, Smithers 1971, Smithers 1983, Stevenson- Hamilton 1947, Stewart and Stewart 1963, Stuart 1975, Tinley 1969, Van Bruggen 1964, Walther 1984, Wilson 1969, Wilson and Keer 1969.