Introduction to Antelope & Buffalo

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Module # 2 – Component # 2

Tribe African African Genera Species Cephalophini: duikers 2 16 Neotragini: pygmy antelopes (dik-dik, suni, royal 6 13 antelope, klipspringer, oribi) Antilopini: gazelles, springbok, gerenuk 4 12 Reduncini: reedbuck, kob, waterbuck, lechwe 2 8 Peleini: Vaal rhebok 1 1 Hippotragini: horse antelopes (roan, sable, oryx, 3 5 addax) Alcelaphini: hartebeest, hirola, topi, biesbok, 3 7 wildebeest Aepycerotini: impala 1 1 Tragelaphini: spiral-horned antelopes (bushbuck, 1 9 sitatunga, nyalu, kudu, bongo, eland) Bovini: buffalo, cattle 1 1 Caprini: ibex, Barbary sheep 2 2 Total 26 75

FAMILY TRAITS

Horns borne by males of all species and by females in 43 of the 75 African species.

Size range: from 1.5 kg and 20 cm high (royal antelope) to 950 kg and 178 cm (eland); maximum weight in family, 1200 kg (Asian water buffalo, Bubalus bubalis); maximum height: 200 cm (gaur, Bos gaurus).

Teeth: 30 or 32 total (see Component # 1 of this Module - Introduction to Ruminants).

Coloration: from off-white (Arabian oryx) to black (buffalo, black wildebeest) but mainly shades of brown; cryptic and disruptive in solitary species to revealing with bold, distinctive markings in sociable plains species.

Eyes: laterally placed with horizontally elongated pupils (providing good rear view).

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Scent glands: developed (at least in males) in most species, diffuse or absent in a few (kob, waterbuck, bovines).

Mammae: 1 or 2 pairs.

Horns. True horns consist of an outer sheath composed mainly of keratin over a bony core of the same shape which grows from the frontal bones. Keratin, a tough, horny substance, is also the main constituent of hooves, nails, claws, hair, scales, and feathers. Horns grow slowly from an epidermal layer surrounding the bony core and if broken or cut off do not regenerate. They are never branched or shed like deer antlers, which are made of solid bone.

Horns evolved before hair, first in the dinosaurs, later in rhinoceroses, and at least 3 times in different families of ruminant artiodactyls. But the structural plan of bovid horns is unique to this family. Horns are the weapons with which males of all species compete for dominance and reproductive success. Horns are present in the females of 43 African species, but are generally smaller and invariably thinner and weaker, reflecting much less rigorous testing in combat. There is growing fossil evidence that horns evolved first in males, and only later in females of different lineages and at different times. The conventional view of female horns is that they evolved as weapons of self defence.

Introduction to Antelope & Buffalo

Family Bovidae

But according to my own theory (Estes 1991), females of polygynous species evolved horns to mimic the horns of their male offspring as a way of reducing harassment of adolescents by mature males, which leads to their separation from female herds with consequent higher mortality. When horns are present in both sexes, they cease to be badges of male- ness and so young males are less likely to be singled out until they cease to resemble females. In species such as oryxes and wildebeests, the resemblance continues into adulthood and facilitates the formation of mixed herds in these migratory/nomadic antelopes.

Thus, although females of all horned species surely do use their horns as weapons, in my view this is a secondary or derived function.

Like other male secondary sex characters, horns are the products of sexual selection and the degree of development reflects the degree of male competition. Thus, horns are no more than simple spikes in the monogamous duikers and dwarf antelopes, but huge and elaborate in many of the highly polygynous species like the impala, sable, greater kudu, goats, and sheep.

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DISTRIBUTION.

Africa is the land of antelopes. Wherever vegetation grows, one species or another has adapted to eat it, from the depths of the Sahara, where the critically endangered addax formerly held sway, to the depths of the Equatorial Rain Forest, where duikers live; from swamps (sitatunga and lechwe) to the Afro-Alpine Biome (bushbuck, eland, duikers). Seventy-two of the 75 bovids are antelopes.

The African buffalo is the only bovine that occurs naturally in the Ethiopian Faunal Region. Sheep and goats, which belong to the Eurasian fauna, have 2 African representatives, the aoudad or Barbary sheep (Ammotragus lervia) and the ibex (Capra ibex); they range as far south as the Sahel (arid zone between Sahara Desert and Northern Savannah) and the Abyssinian Highlands.

Only two tribes of African antelopes occur outside the continent: the Antilopini, with 9 out of a total of only 12 Asian antelopes, and the Arabian oryx (Oryx leucoryx) which gives the Hippotragini a foothold on the Arabian Peninsula.

What exactly is an antelope? Technically, it is the name of the Indian blackbuck, Antilope cervicapra, and applies to the members of its tribe, the Antilopini. In practice, bovids of all tribes apart from cattle (Bovini), sheep and goats (Caprini), and goat- antelopes (Rupicaprini) are called antelopes. But in fact, antelopes from different tribes are as unalike as are sheep and cattle. The 9 tribes of African antelopes thus represent a diversity of bovids far greater than on any other continent, either now or in the past.

THE AFRICAN BOVID RADIATION

The extraordinary diversity of African antelopes can be attributed to a number of inter-connected factors

I. The African continent is unusually large and physiographically diverse. It has by far the largest tropical land mass, being the only continent that spans both tropics. The great variety of life zones (biomes) that presently exist began to differentiate during the middle Miocene, providing new and shifting ecological opportunities for the bovids to exploit. (See table 1.1).

II. The bovid array represents the most recent ungulate radiation, which reached its peak within the last several million years in the Pliocene and Pleistocene. Although Africa, like the other continents, had its share of Pleistocene extinctions, most of the genera and species of antelopes that ever existed are still with us.

III. The African fauna has been repeatedly enriched by immigrations from Eurasia during extended periods when land bridges connected the 2 continents. The earliest known bovid, the gazelle-sized Eotragus, occurred both in Europe and North Africa 20 million years ago. By the late Miocene, African bovids had diversified into 9 distinct tribes, but most had Asian

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relatives. A massive invasion of Asian genera in the early Pliocene, followed by differentiation of African types, resulted in a major faunal revolution: over 85% of the Pliocene genera are new, including 9 genera of bovids, of which all but 5 are unknown outside Africa. As late as the early Pleistocene, new genera continue to appear in the fossil record, due both to Asian immigrants (8 more bovid genera) and in situ evolution. The duikers, neotragines, and reedbuck / kobs are the only bovid tribes that evolved in Africa and never reached Asia.

IV. The Sahara Desert has imposed a formidable barrier to intercontinental movement since the second half of the Pleistocene, as reflected by a much higher proportion of endemic African mammals. Eurasian species could still disperse to North Africa but only desert-adapted forms could penetrate the Sahara. Most of the Eurasian tropical-savanna fauna proceeded to become extinct during the Ice Age, leaving Africa as the final refuge of Plio - Pleistocene mammals.

V. Speciation within Africa was promoted by expansion and contraction of the Equatorial Rain Forest during wet (pluvial) and dry (interpluvial) periods of the Ice Age. During pluvial periods the rain forest stretched from coast to coast, barring interchange between northern and southern savanna and arid biomes but facilitating the dispersal of forest forms. In succeeding interpluvials the rain forest was reduced to a number of isolated islands, and a drought corridor extending through eastern Africa connected the savanna and arid biomes; this explains the presence of some of the same mammals in the Somali and South West Arid Zones, separated by the whole Miombo Woodland Zone, for instance the oryx, dik-dik, steenbok, bat-eared fox, and springhare (Pedetes capensis).

VI. A fundamental reason for the great diversity and success of the bovids is their ability to specialize more narrowly and efficiently than other ungulates. By tailoring size, feeding apparatus, digestive system, and dispersion pattern for a particular set of ecological conditions, antelopes have effectively partitioned African ecosystems into many small segments.

Tribal Niches

A commitment to one type of biome or another is seen in most of the tribes and genera and presumably dates back to the original differentiation of tribes in the Miocene and Pliocene.

?? Gazelles and other Antilopini are specialized for arid biomes; they are medium-sized, wide-ranging gleaners which can subsist in areas too dry and poor to support larger roughage eaters. A Gazella species was roaming the Kenya plains 14 million years ago. ?? The neotragines are small antelopes, allied to the gazelles, that lead sedentary, solitary lives within various closed habitats, from rain forest to sub- desert. ?? The duikers are specialized as forest fruit- and foliage-eaters.

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?? Members of the bushbuck tribe are medium and large browsers that inhabit mostly closed habitats, from forest to sub-desert thornbush.

The remaining 4 tribes are grazers that have specialized for different grassland habitats.

?? Cattle and the reduncines live in valley and floodplain grasslands within a short distance of water. ?? Alcelaphines disperse into dry savanna during the rainy part of the year and concentrate on greenbelts near water points in the dry season. ?? Hippotragines include the desert-adapted addax and oryx as well as the water-dependent sable and roan, which inhabit the well-watered savanna woodlands. These ecological specializations are considered in more detail in the tribal introductions and species accounts.

PHYSIOLOGICAL ADAPTATIONS FOR ARID CONDITIONS.

Vast regions of Africa and Asia are uninhabitable or only seasonally habitable by animals dependent on drinking water. Bovids able to obtain all the water they need from their food can exploit the vegetation of arid lands and thereby avoid the more rigorous competition for plants within commuting distance of water.

Browsers in general are less water-dependent than grazers, mainly because bushes and trees can reach down to moist soil and produce green growth at times when grasses are parched. Moreover, many plants of arid and semiarid environments have water-storage organs such as thickened roots and tubers or succulent stems and leaves. Parts of the Kalahari sandveld produce such an abundance of melons and tubers that even water-dependent grazers like the wildebeest arid hartebeest are able to live there without surface water. However, antelopes such as most gazelles, oryxes, and dik-diks require less water to survive, especially when it is extremely dry and hot. The key physiological adaptations include:

1) Allowing body temperature to rise 2) Lowered metabolic rate, decreasing with dehydration 3) Reflecting coat: flat, dense, short, smooth, light colour 4) Concentrating urine; extracting moisture from faeces 5) Nasal panting and cooling of the blood to avoid overheating

Allowing body temperature to rise with environmental temperature - by as much as 10 °C - is the most important water-conservation measure, one that is also employed by camels. Desert-adapted species can let their body temperature go higher for longer than can other antelopes. To maintain a constant body temperature on a hot day requires water for evaporative cooling, even though the common bovid technique of closed-mouth panting is much less wasteful than sweating. Air passed across the nasal mucosa while breathing rapidly cools the blood by evaporating moisture from the nasal mucosa. The cooled venous blood then flows through a capillary network (the rete mirabile) surrounding the carotid arteries, where it cools the blood going to the brain.

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CORRELATIONS BETWEEN HABITAT PREFERENCE, MORPHOLOGY, ANTIPREDATOR STRATEGY, AND SOCIAL ORGANIZATION

Table 2.1 Correlations Between Social Organization and Selected Traits of the 75 Species of African Bovidae Soli Greg- X2 tary arious Total number of species 32 43 Habitat preference Closed 30 9 Open 2 34 39.98 Diet a Browse or mixed (browse and grass) 31 21 a Primarily grass 3 20 10.98 Size Small to medium (1.5-45 kg) 28 10 Medium to large (45-950 kg) 4 33 30.29 Conformation Rounded back, massive hindquarters, short legs 31 12 Cursorial (long legs, back level or high 1 31 32.91 shoulders) Coloration Concealing (cryptic or disruptive) 31 12 Revealing (contrasting color and/or markings) 1 31 32.91 Male horns Primitive: short, straight spikes or forward hooks 30 3 Advanced: medium to large size or complex 2 40 52.60 shape Sexual dimorphism (in body size, horns, coloration, or other male secondary characters) Minimal 29 13 Pronounced 3 30 27.16 Antipredator strategy of adults Concealment or flight to cover/sanctuary 32 13 Avoid cover and flight in open 0 30 32.16 NOTE: All the chi-square values are highly significant (P < .010, 1 df). a includes 4 of the least sociable gregarious species: gerenuk, dibatag, mountain reedbuck, and sitatunga.

An analysis of the 75 species of African bovids indicates that habitat preferences, diet, size, conformation, gaits, coloration, anti-predator strategy, degree of sexual dimorphism, mating system, and social organization are all co-adapted. In table 2.1 a basic dichotomy in the traits of solitary and gregarious species is demonstrated by the results of a series of correlation tests. The significance of these differences is illustrated by comparing the traits of forest duikers, representing solitary antelopes adapted for closed habitats, with the adaptations of an oryx, an advanced open- country antelope (table 2.2).

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The duikers' conformation, short, slanted horns, and gaits are designed for movement through and under dense vegetation, often on soft ground (hence the splayed hooves). The presence of undergrowth, intimate knowledge of a small home range, small to medium size, cryptic coloration, and solitary habits all support a concealment strategy. The oryx's build and gaits are adapted to travelling long distances across arid, often hard ground (hence the compact hooves). Fleet and enduring, big, well-armed and aggressive, the oryx is well-equipped to escape, and even defend itself against, predators. Although the newborn are concealed, adults avoid heavy cover. Water - independence enables the oryx to reside in arid regions that are permanently or seasonally beyond reach of water-dependent species.

Group formation is a basic adaptation to life in the open; the oryx goes further and lives in mixed herds, apparently as a specialization for a sub-desert biome where overall population density is very low. The long, straight horns and conspicuous markings serve as species-recognition characters that make an oryx unmistakable for any other animal.

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Mating System, Age at Maturation, and Sexual Dimorphism.

Sexual dimorphism in bovids, as in most mammals, is the result of male reproductive competition, which causes males to acquire physical and behavioural traits that enhance their ability to compete successfully. The greater the potential reproductive success, that is, the more females with which a male may mate - the more polygynous, the greater the sexual competition and the greater the degree of sexual dimorphism that is likely to develop. The different types of social organization and mating systems are considered below.

In a monogamous system, with only one female for each male, male sexual competition is minimal and consequently there is little dimorphism - the sexes look much alike (unimorphic or unisex). In fact, females tend to be slightly larger than males in the duikers and dwarf antelopes. In all the other tribes, males mature later and end up larger than the females.

The degree of size dimorphism within a species increases with the difference in age at maturation; it is much greater in species where males mature 3 or 4 years later than females than where the difference is only 1 or 2 years. This helps to explain why the most pronounced dimorphism occurs in bovids of medium and large size, for development takes longer than for smaller species. Dimorphism is particularly developed in the Reduncini (kob, lechwe) and Tragelaphini (nyala, sitatunga, kudu, eland).

But the sexes look much alike in the Alcelaphini and Hippotragini, which include 8 of the 18 most gregarious antelopes. These species, though polygynous, share the tendency to form mixed herds containing adults of both sexes. Sexual segregation, conversely, increases with increasing sexual dimorphism. The correlation between these tendencies in the 43 gregarious African bovids is highly significant (table 2.3). Apparently, selection for uniformity exists in species like oryx and wildebeest that are under ecological pressure to integrate, and counteracts selection for sexual dimorphism.

Concerning the forms of sexual dimorphism, contrasts in horn development are often more apparent and only slightly less common than size dimorphism. Next commonest is colour dimorphism. In the sable, kob, lechwe, nyala, eland, and other Tragelaphines, for instance, adult males become much darker than adult females.

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Thick necks are an obvious attribute of adult male Grant's gazelles, gerenuks, impalas, kobs, reedbucks, sables, elands, and buffalos, whereas male Tragelaphini grow conspicuous beards or manes. In the eland and buffalo bulk, especially of the neck and shoulders, distinguishes mature bulls.

SOCIAL ORGANIZATION

Despite tremendous variation in the grouping and dispersion patterns of African bovids, all of them can be placed in 4 different categories: solitary or gregarious, territorial or non-territorial. The characteristics of each type, and some basic variations, are outlined here and detailed in the tribal and species accounts.

1) Solitary/Territorial. The dik-diks, steenbok, klipspringer, oribi, and other dwarf antelopes, and at least some duikers, live in monogamous pairs and jointly maintain a small territory they seldom or never leave. Each member of the pair excludes outsiders of its own sex, they mark the territory with preorbital - gland secretions and/or dung middens, and maintain the pair bond by frequent tactile and olfactory interactions. Young of both sexes disperse during adolescence, the sexes develop at nearly the same rate, and as usual in monogamous mating systems, the adult sex ratio is equal. Males have to win a territory and females have to find an unmated male before they can reproduce. Two of the 3 reedbucks also live in monogamous, territorial pairs, but one of them has a tendency to polygyny and often forms loose herds away from cover, thus showing a certain gregarious tendency (see reedbuck account).

2) Gregarious/Territorial. Females and young associate in herds that usually contain 1 adult male, namely the owner of the territory on which the females are visiting or residing. Males without territories associate in bachelor herds, which are generally kept segregated from females and young by the intolerance of the territory owners. Female offspring are free to remain in their natal herd and traditional home range indefinitely, whereas males are forced to disperse when they acquire obvious male secondary sex characters. Higher mortality rates associated with dispersal and competition between adults for territories lead to adult sex ratios skewed in favour of females, thus promoting polygyny.

The gregarious/territorial form of organization is prevalent among African antelopes except for the 2 groups of solitary species (Cephalophini, Neotragini) and the spiral- horned antelopes (Tragelaphini). Probably most antelopes are distributed as resident populations, wherein males hold the same territories year in and year out. However other species, and also populations of the same species, may be migratory for some or all of the time, dispersed at one season and aggregated at another, etc. The territorial system is extremely adaptable and variable, as the following examples illustrate.

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?? Conditions that intensify competition. Generally speaking, male competition tends to be more rigorous in species and populations that have a limited rutting season than in those that breed perennially (see impala and kob accounts); within populations living at high density in large herds; between territorial males who live within plain view of each other on small territories; and earlier rather than later during each individual's territorial tenure.

?? Lek breeding. Males crowd together on a traditional mating ground, where females come individually to breed with the males holding the most central places. Known only in the kob, lechwe, and topi, this is perhaps the most polygynous and competitive form of territoriality. Leks only occur at high density.

?? Temporary territories. In migratory populations, males only become territorial when the aggregation they are accompanying stops travelling. Their behaviour is then perfectly comparable to that seen in resident populations, although territorial density and competition are both increased. When general movement resumes, the bulls abandon their places one by one and rejoin the migration. (See wildebeest, topi, and Thomson's gazelle accounts.)

?? Transition to rank-dominance system. In the oryx, as already noted, herds commonly contain adult males as well as females. However, 1 male is dominant and monopolizes any oestrous females. The only obvious difference from a typical rank-dominance system is the presence of isolated and apparently territorial bulls which may be dominant to all males in herds.

?? Satellite males. In the waterbuck, desirable territories may be so much in demand that the best way for a maturing male to gain one is to live as a resident satellite and wait for the owner to die or grow old.

3) Solitary/Non-territorial. The bushbuck is the only African bovid in this category. Each adult has a small, exclusive core area where it rests and hides, but home ranges overlap extensively. Individuals from the same locality are loosely associated but do not herd together. The sitatunga, in which a couple of females and their young may form loose herds, represents a transition between solitary and gregarious versions of this system.

4) Gregarious/Non-territorial. In addition to the spiral-horned antelopes, cattle, sheep, and goats also belong in this category. In all these tribes, male reproductive success is based on absolute dominance over other males rather than on dominance at a particular site. This more direct form of competition places a premium on size and power; to achieve them, males spend more years growing than in most territorial species, maturing typically several years later and growing much larger than conspecific females. In buffalo and other Bovini, males may continue growing for most of their lives, making dominance largely a function of seniority. In kudu and nyala, as in sheep and goats, horns continue growing after maturation, so that in these species length and shape are reliable indicators of age and fighting potential. In territorial species, horns

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reach their maximum development at maturity; therefore their size and shape serve only to distinguish adult from younger age classes.

Segregation of the sexes except for breeding is the rule in gregarious/non-territorial systems, but there are always exceptions. The African buffalo, for instance, lives in mixed herds.

ACTIVITY

Most bovids and other ruminants alternately feed and ruminate both day and night (62 species plus 22 probable out of 93 ruminants that were assessed). Concentrate selectors tend to feed and digest in relatively short bouts, whereas roughage feeders, with a larger capacity and slower digestion, eat and ruminate at longer intervals (see Component # 1 of this Module).

The only strictly nocturnal or diurnal ruminants are forest frugivores, namely duikers and the water chevrotain, which are small enough (30-40 kg) to gain practically all the nutriments they need by eating fallen fruits for some hours of the day or night. Although some other bovids are apparently more active by night than by day (e.g., buffalo, bushbuck, reedbucks, dik-diks, grysbok), generally bovids move more in daylight, especially early and late in the day, which are also times of peak feeding and social activities.

Most animals remain relatively inactive during the hottest hours. There is usually one major feeding peak at night, framed by long rest periods after dark and before dawn.

POSTURES AND LOCOMOTION

Differences in the conformation and locomotion of bovids that live in closed and open habitats have been noted (tables 2.1 and 2.2) and discussed. It should be added that bovids with a duiker-like conformation (short and/or sturdy legs, overdeveloped hindquarters), which live in cover, or in very uneven or steep terrain, characteristically walk with a diagonal stride, the cross-walk, whereas long-legged species and those with overdeveloped forequarters (e.g. wildebeest / hartebeest tribe) that live in open, comparatively level country typically amble, moving the legs on the same side of the body together, as in pacing. The latter gait is virtually unknown in bovids, which all trot in a diagonal stride. Duikers, dwarf antelopes, the bushbuck and other Tragelaphines, goats and sheep, and cattle are all cross-walkers, whereas the tribes represented by gazelles, wildebeest / hartebeest, waterbuck, and oryx are all amblers.

Although all bovids probably can and sometimes do trot, and certain species (e.g., oryx, gerenuk, eland) even favour this gait, for most species it is the least-used gait. A relatively few species (e.g. wildebeest, topi, oryx, sable, dorcas gazelle) perform an exaggerated style-trot, in which the forelegs are lifted high, when mildly excited or alarmed, as an alternative or in addition to trotting. Stotting, a high, straight-legged

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bounding gait (fig. 2.2), is widespread among plains antelopes, including gazelles, topi, hartebeest, dik-dik, oribi, etc., most of which have a white rump patch that adds to the conspicuousness of this display. Apart from expressing excitement, stotting clearly functions as an alerting or warning signal when performed by, for instance, a gazelle fawn that has been flushed from hiding.

Differences in the way antelopes run are too complex to discuss in detail here, but follow from differences in size, general conformation, and relative limb development and length. The high, bounding gallop of a reedbuck, the laboured run of a bull eland, and the ground-gaining lope of migrating wildebeests illustrate the range of differences that exist. Postures associated with displays are considered separately. Resting postures are discussed in Component # 1.

Grooming and Comfort Movements.

Probably all bovids scrape their coats with their lower incisors and nibble-groom with their lips; a smaller number lick themselves (duikers, cattle, and bushbuck tribes), although perhaps all clean their nostrils by inserting the tongue. The shoulders, tail, and back, followed by other areas in reach of the mouth, are the places most frequently groomed. The cheek and the side of a horn are often used to brush the withers with a sweeping movement over the shoulder. In long-horned species, the horn tips are used to scratch the back or rump.

The hind feet are employed to scratch the head, ears, eyes, between the horns, neck, chest, and upper forelegs. Insect pests are warded off by wagging or clamping the tail, raising and vigorously shaking the head and flapping the ears, hitting shoulders and sides with the head, twitching the flank skin, shuddering the legs, and stamping.

Wallowing or rolling in mud or dust is rare in antelopes. Wildebeests are the only ones that roll; these two species, hartebeests, and topi also rub their heads and horns in mud, then smear themselves. The buffalo is the one confirmed wallower among African bovids.

SOCIAL BEHAVIOUR COMMUNICATION

Bovid visual displays are considered in a separate section following Anti-predator Behaviour. Vocal, olfactory, and tactile communication are treated in the tribal and species accounts.

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AGONISTIC BEHAVIOUR

The various displays associated with aggression, fear, and uncertainty are catalogued in table 2.4 (which can be found in Module # 2 Component # 3).

Fighting Behaviour.

The different forms of fighting practiced by African bovids reflect the great morphological variety that is represented in 2 different tribes. Similarities in fighting techniques are discernible within tribes, the more closely related the more alike. Thus, all members of the hartebeest tribe always fight on their knees, and the horse antelopes usually do so. The sitatunga, bushbuck, and bongo do so occasionally. All other African bovids normally remain on all fours during combat. But form also affects function, and fighting behaviour is particularly complex and variable. Thus, Gazella species of different size with horns of different proportions have different fighting techniques. Species with similar horns, even though only distantly related (e.g. kob and impala, sable and ibex, kudu and addax), might be expected to fight in similar fashion, and indeed may, but still within the constraints of phylogenetic differences.

The difficulty of describing and comparing fighting techniques is compounded by the fact that the repertoire of each species includes several different techniques and these varied and complex behaviour patterns have so far been studied in only a few species. Consequently only a superficial treatment can be given here. The information and descriptions are based on the work of Fritz Walther.

Horns normally have sharp points, capable of penetrating even the thick skin which forms a shield over the neck and shoulders of males in some, perhaps most bovids. Once I found a dead male Thomson’s gazelle that had been stabbed in the heart, presumably by a rival's horn. Yet stab wounds and other serious injuries are very rare. Why?

?? When bovids fight, they normally direct their attacks to the opponent's head and not the body, and alignment during the fights of all African bovids is head to head. Although several species also fight while standing parallel, these are special and not their main fighting techniques.

?? Except in their most primitive form - short spikes and hooks - horns are designed as much for defence as for offence, serving to catch and hold the opponent's horns, thus preventing the tips from pressing into the skin. S- shaped horns (e.g. impala, kob, lechwe) have up to four functionally different sections: the stem or base for protecting the skull; a thickened convex section for ramming; a concave section for catching and holding the opponent's horns; and the smooth, sharp tips for stabbing. The ridges or annulations that occur in the majority of species not only add structural strength but also help bind opponents' horns together.

?? The purpose of fighting is to determine which of two contestants is superior. Therefore, contests are normally between individuals of approximately equal size and fighting prowess. Animals that are clearly out-matched, for instance immature males threatened by individuals of older and bigger classes, will run

away rather than fight. At the same time, the risk of predation resulting from even minor injuries selects in favour of individuals that know when to quit - that goes for winners as well as losers. The very act of fighting is also a time of particular danger, and individuals which engage in protracted, all-out combat may well be caught in the act by some wide-awake lion.

?? Consequently, fights are normally a simple trial of strength, in which the combatants are equally adept in offence and defence and rarely gain the opportunity to break through the opponent's defences and gore him. Fights usually end either in a draw or in the flight of the loser.

?? Yet, though damaging fights are rare, probably every male is battle-tested at some point in the course of maturing and winning the right to reproduce. The incidence of broken horns, though never more than a small percentage of the adult males, is evidence of severe fights in which the quite incredible stress necessary to break a male's horns was exerted.

?? The fact that attacks are rarely directed to the body may reflect some inhibition and the existence of fighting conventions. However, such inhibitions tend to disappear in serious fights and/or when one is the clear winner. The loser is at serious risk when he gives up and flees, for often the victor tries to gore a fleeing rival in the backside. But by exerting himself to the utmost, the loser nearly always manages to escape un- scathed.

Fighting Techniques.

The most basic forms of combat are outlined here, with examples of the species that employ them, beginning with the most common. The position of the head, and the movements of the head and neck which are associated with these different forms, are listed and illustrated (fig. 2.3), and major variations in the form are noted. See the tribal and species accounts for more detail.

Boxing. Low-intensity fighting in which the chin is drawn in until the horns of two opponents come into contact, a movement called nod-butting. Examples: sparring gazelles, topis, hartebeests.

Clash-fighting and fencing. Contestants exchange hard blows at short range, jumping backward between butts. Associated head and neck movements: forward- down- ward blows, push-butting and forward- pushing (less commonly forward- swinging, sideward-pushing and -swinging). This style becomes front-pressing when combatants lock horns. Examples: the prevalent style of small gazelles (subgenus Gazella), also topi/blesbok and waterbuck. Variations: fencing oryxes exchange short but strong forward and sideward blows of their long, straight horns while confronting with lowered heads, usually while remaining in one spot. The ibex and other goats rise on their hindlegs as a prelude to clashing horns, thereby intensifying their forward- downward blows.

Push-fighting. A transitional form between clash-fighting and front-pressing (the next style). Combatants press forward instead of disengaging, but without locking horns. Associated fighting movements are chiefly push-butting and forward- pushing.

Front-pressing. With horns crossed and firmly anchored near their bases and heads lowered parallel to the ground so that the horns point forward, combatants strain to push one another backward, employing the full array of fighting movements (forward, sideward, upward, twisting, and even backward). Examples: best developed in species with long horns, especially common and pronounced in combats of Grant's gazelle, impala, kob, lechwe, waterbuck, oryx, kudu, and eland.

Thrust-fighting. All-out fighting, in which combatants jump into contact and keep thrusting forward with all their might. Thrust-fighting develops from clash-fighting or front-pressing. Examples: unusually severe fights between male gazelles, alcelaphines, and hippotragines.

Ramming. A form of clash-fighting practiced by species whose horns and skulls are specially adapted to absorb shock, notably bighorn sheep and bovids with massive horn bosses such as the African buffalo. Combatants take a running jump and bash heads with tremendous force (cf. combat of giant forest hog).

Hooking. Side-to-side (pendulum) head movements. This is not a separate technique but performed in combination with other fighting styles, as during thrust- fighting and front-pressing. Example: wildebeests during hard fights.

Lever-fighting. The same movements as in hooking, when combatants' horns are crossed and anchored. Seen mostly in long- horned species such as Grant's gazelle, waterbuck, kudu, and other tragelaphines during front-pressing fights.

Fight-circling. Pivoting, meanwhile violently pulling and jerking, that occurs when combatants fighting with horns firmly locked have difficulty disengaging. Observed instances: Grant's gazelle, greater kudu, springbok--and once only, two wildebeests (C. taurinus)

Horn-pressing. Two combatants standing close together in medial-horn presentation engage the front surfaces of their horns. Each then tries to force the other's horns back onto its neck. This technique carries over into front-pressing when the horns become interlocked. Quite a wide-spread technique but most developed in longer horned species such as Grant's gazelle and especially antelopes with convoluted horns such as the kudus (see fig. 9.9).

Parallel fighting. A few species stand side by side or at an angle, and with horns interlocked, neck-wrestle or push sideways with horns, and/or attempt to hook sideways and backward, over or under the opponent's guard. Examples: oryx, roan, and sable all fight in this way, but mainly as a form of sparring between immature males. The aoudad and some other bovids with hooked horns that extend sideways also engage in parallel fighting, with their inside horns interlocked.

Air-cushion fighting (or shadow-boxing). Two combatants may perform all the different attacking and parrying manoeuvres that are used in real fights, but without actually making contact - as though an invisible cushion had been placed between their horns.

REPRODUCTION

All African bovids bear one young and breed at least once a year (small species often twice), giving birth to well-developed young after gestation periods of about 6 months (dwarf antelopes and gazelles) to 8 or 9 months in medium and large species.

A female's maximum life- time production of offspring has been found to be about 14 for both small and large species. Most species have extended but definite breeding seasons during the rainy part of the year and, in equatorial regions with two rainy seasons, many have a secondary calving peak. Females of perennial and semi- annual breeders re-enter oestrus within a month or two after calving (postpartum oestrus). Sexual displays are described under Communication (see table 2.4).

SEXUAL BEHAVIOUR

Oestrus generally lasts for no more than a day in territorial species. But in non- territorial species (bovines, Tragelaphines), in which males seek out and attempt to maintain exclusive tending bonds with oestrus females, oestrus lasts for several days, at least. Female receptiveness is usually signalled simply by readiness to permit mounting and by moving the tail aside to permit intromission.

Copulation takes a few seconds at most, consisting of a single ejaculatory thrust following intromission. Male copulatory postures differ between tribes but tend to be the same within tribes.

PARENT/OFFSPRING BEHAVIOUR

In the monogamously paired duikers and dwarf antelopes, the male may come to the defence of his own offspring. In polygynous species, males usually provide no parental care. The offspring of all but two tribes of African bovids are hiders: calves remain concealed anywhere from a week or less up to 2 months, depending on species, emerging only when summoned by their mothers to nurse; afterward the calf seeks a new hiding place on its own initiative. An elaborate concealment strategy reduces the chances of predators finding hidden calves (e.g. see Grant's gazelle account).

Newborn young lie still unless in imminent danger of discovery. Their scent glands remain inactive during the concealment stage, and body wastes are retained until the calf is stimulated to void them by the mother's licking. The mother typically remains on guard but stays away from the hiding place and retrieves her offspring no more than 2-4 times in a 24-hour period.

When moving with the mother, a hider calf does not travel beside her but alternately runs ahead and lags behind her. Even after the concealment period when they join the herd, hider calves spend relatively little time in their mothers' company. The more

sociable species stay together in peer subgroups (crèches) and seek out their mothers only to nurse and when the herd undertakes general movements.

Follower calves accompany their mothers from the time they first gain their feet and do not go through a lying-out stage. The only examples among antelopes occur in the Alcelaphini, where the wildebeests have evolved a unique system as an adaptation to migratory habits and dense feeding aggregations. Groups of calves serve as "cover" for newborn individuals during an abbreviated postnatal feeble period, and the year's calf crop is produced within a few weeks (see tribal and wildebeest accounts). Only the mother actively defends her calf against predators, whereas the buffalo and other bovines have evolved a group defence. Yet another system is deployed by sheep and goats, which rely on cliffs as refuges for both adults and young.

ANTIPREDATOR BEHAVIOUR.

See Alerting and Alarm Signals, table 2.4, and tribal and species accounts.

SOURCES

Bell 1982, Darwin 1871, Dement and Van Soest 1985, Bubost 1983. East 1984, Emlen and Oring 1977, Estes 1969, Estes 1972, Estes 1974a, Estes 1991, Finch 1972, Geist 1966, Geist 1974, Gentry 1978, Georgiadis 1985, Gosling 1981, Heintz 1969, Janis 1982, Jarman 1972b, Jarman 1983, Kiley 1972, Kingdon 1982, Lent 1974, Maglio 1978, McNaughton and Georgiadis 1986, Owen-Smith 1977, Packer 1982, Smith 1978, Taylor 1969, Taylor 1970b, Taylor and Lyman 1972, Tinbergen 1964, Walther 1958, Walther 1978a, Walther 1979, Walther 1984, Walther, Mungall and Grau 1983, Spinage 1986.