Status and general aspects of the ecology of black wildebeest and present-day threats to the survival of the species

Status and general aspects of the ecology of black wildebeest (Connochaetes gnou) and present-day threats to the survival of the species

Savvas Vrahimis
Free State Department of Tourism, Environment & Economic Affairs
Scientific Support Services
Private Bag X 20801
Bloemfontein
9300

“A more whimsical compound than the Gnoo could scarcely have been thrown together, or a monster imagined of more fantastical and anomalous exterior” – W. Cornwallis Harris, 1840

Introduction

The Black Wildebeest found today are only remnants of the large herds which were known to have roamed the plains of South Africa in the past. These remaining animals are at present all confined to nature reserves and private game farms where the large-¬scale migrations, as historically described, are no longer possible. Their confine¬ment to relatively small areas has led to management problems in most regions. In order to address some of these pro-blems and to obtain more insight into the functioning of the species, a project investigating various aspects of the ecology of Black Wildebeest was initiated in 1980. The information presented in this article is based on the research done by the author in the Free State. How¬ever, these findings are probably applicable to Black Wildebeest populations in other parts of South Africa.

Historical background and distribution

The Black Wildebeest or White-tailed Gnu is endemic to South Africa, historically occupying the central open plains of the country. Essentially, the species was found in the Grassveld and Karoo regions of the central and northern Cape, the whole of the Free State and the southern highveld regions of the former Trans¬vaal (Von Richter, 1971a). It was also recorded in western Lesotho and the Grass¬veld areas of western Swaziland. In KwaZulu-Natal, there are reports of Black Wildebeest having occurred in the open Grassveld areas below the Drakensberg range.

This species attracted much attention from most early explorers in South Africa. Vivid descriptions of vast herds with animals performing curious pran¬cing movements can be read in the diaries of these travelers. This peculiar behaviour resulted in Black Wildebeest often being called the "clowns of the veld". The strange appearance of the animal was apparently a cause of embar¬rassment for early naturalists who were confused with the classification of an animal which has "the mane and tail of the horse; the form of the head and the horns resemble the ox; and in the legs and delicate make of the body it appears of the antelope species" (Lichtenstein, 1930).

Millais (1895) referred to this ex¬traordinary-looking creature as being the most interesting animal in the world and expressed his concern, fearing the ex¬tinction of the species. He stated that formerly, "tens of thousands of these Wildebeest had been scattered in troops of from twenty to fifty over the whole face of the southern Transvaal and the Free State Highveld - and then after careful inquiries there were hardly more than 550 in existence (in the early 1890s)".

This drastic decline in Black Wildebeest numbers can be attributed to various factors. The senseless slaughtering of the animals, which initially started off as hunting for provisions, and then later escalated to the wanton killing of the animals for their skins only, can probably be listed as being the primary reason. Trade in game skins had become a flourishing business and it was reported that a single firm in Kroonstad exported 157 000 Black Wildebeest and Blesbok skins in 1866 alone (Garson-Steyn, 1964). In 1870 and 1871 nearly half-a-¬million Blesbok, Wildebeest and Zebra skins were shipped from Durban.

The eastern Free State, where most of the slaughtering took place, still bears the grim name "riemland" (Von Richter, 1971a). In addition, descriptions by explorers and hunters, such as Corn¬wallis Harris (1840), of heaps of as many as two or three hundred rotting skulls, are evidence of the periodic outbreaks of diseases which ravaged Wildebeest herds.

Finally, the increasing human settlements and their subsequent expansion, restricted the movements of Wildebeest herds, and rendered large areas unsuitable for them (Von Richter, 1971a).

The status of Black Wildebeest

After being a rare and endangered spe¬cies for many years the Black Wildebeest is now relatively safe from extinction, thanks to a few conservation-minded farmers in es¬pecially the Free State and former sout¬hern Transvaal. This achievement can probably be considered as being one of the few conservation related success sto¬ries that can be boasted of in South Africa.

The first comprehensive census was carried out during 1945 which showed a total of 1 048 Black Wildebeest in South Africa (Bigalke, 1947). He however, suspected that a number of herds had not been located. Twenty years later re-sults of a national survey were published by Brand (1965), in which 1 808 ani-mals were traced. In a third survey con¬ducted in 1970 (Von Richter, 1971), the numbers had increased to 3 120 Black Wilde¬beest. Results of a total game census conducted by Terblanche (1988) in the Free State only, showed 6 500 and 7 680 Black Wildebeest in 1980 and1985 respectively.

According to the1991 figures obtained from Wildebeest registration certificate statistics (Department of Agricultural Economics and Marketing) there were approximately  17 493 Black Wildebeest in South Africa at the time. These ani¬mals were distributed as follows:

Province    Numbers:
Free State    9478
Former Cape Province (Western, Eastern and Northern)    4048
Former Transvaal (Gauteng, Northwest, Limpopo & Mpumalanga)    3308
KwaZulu-Natal    659

These figures are probably over¬estimates, with some landowners having indicated the number of animals they would like to have, and not the actual number on their properties.

Presently, the total Black Wildebeest population is estimated at more than 18 000 animals, of which 80% occur on private land and 20% in protected areas. The species has been widely reintroduced within its former distribution range, however, it has also been established extra-limitally within South Africa and on private farmland in Namibia, where importations from South Africa has led to a dramatic rise in the estimated total numbers, from 150 in 1982 to more than 7 000 in 1992 (East, 1998). The population size is increasing, especially on private land. Recently, Black Wildebeest have also been introduced to private farms in Botswana.

Social organization

Von Richter (1971a) identified three social groupings for the Black Wildebeest:

Female herd

These herds consist of adult and sub-¬adult females as well as calves. A number of young bulls may also be present in female herds. In most cases a territorial bull is in attendance throughout the year. The average size of a female herd in the study areas was 28,4 animals.

Members of female herds show strong attachment to their concentration areas and seldom move away. When disturbed they move off their concentration areas but return shortly after¬wards.

Bachelor herd

Bachelor herds contain only adult and sub-adult bulls, with a few yearlings. These animals move about more freely showing less attachment to a specific concentration area. Von Richter (1917a) mentions that a notable feature of these herds is the extreme tolerance of the bulls towards one another. In most cases adult bulls eventually leave these herds and attempt to become territorial bulls. Von Richter (op. cit.) correctly refers to these herds as reservoirs from which replacements for territorial males are drawn, and not as mere aggregations of excess bulls. The average size of a bachelor herd was found to be 20,6 animals.

Territorial bulls

Von Richter (1971a) identified territorial bulls as being the backbone of the population as only these bulls partake in mating. They remain on their territories throughout the year. As described for Blesbok by Lynch (1974), two types of territorial males can be recognized in Black Wildebeest, viz.:

(a) Territorial bulls occupying a relatively small area, with each bull within sight of his neighbour, forming a territorial net¬work. Lynch (1974) states that this net-work is comparable with the lek or arena system of Blesbok, Lechwe and Uganda Kob, which consists of a tight cluster of 10 - 20 small central territories, each occupied by one adult male. In the case of Black Wildebeest, a definite dominance exists amongst bulls in a territorial net¬work. This was established by observing marked animals in such a network over a period of time.

(b) Isolated or solitary territorial bulls which do not belong to a territorial net¬work. These animals are normally out of sight of all other Black Wildebeest. It ap¬pears that these males are the older ter¬ritorial bulls.

Territorial bulls are usually aggressive and perform vigorous territorial displays in their concentration areas. However, should territorial bulls meet in "neutral" or common ground e.g. at a drinking site, no true aggression is shown.

Habitat selection and feeding preferences

The Wildebeest is predominantly a grazer and prefers short grassveld (Von Richter, 1971a). Areas with tall grass are normally avoided. Should animals be forced into parts with tall grass, they quickly transform sections to suit their needs. Also, there is evidence that Black Wilde¬beest choose certain concentration areas not primarily for the grazing quality offe¬red, but for the safety aspect with regard to overall visibility, making it virtually im¬possible to approach these animals with¬out being seen. This is especially notice¬able in areas where Black Wildebeest are often hunted.

The feeding preferences of a tame Black Wildebeest cow was investigated over a two year period in the Rustfontein Dam Nature Reserve. This animal was hand-reared but subsequently integrated into a free-ranging herd. Results obtained from the feeding study showed that this animal utilized grass (93,7%), Karroid shrubs (3%) and herbs (3,3%). While mainly a non-selective grazer there was evidence of some preference for certain grass species.

Activity patterns

The effective management of wild animal populations depends on a thorough knowledge of how each species interacts with its environment. One of the most useful methods for describing this rela¬tionship is to quantify the activity patterns shown in different areas and seasons (Norton, 1981).

The diurnal activity patterns of Black Wildebeest were investigated on a monthly basis over a period of two years. Generally these animals were found to spend the largest part of the day lying down (45,6%) This feature can partly be attributed to high temperatures recorded in the study areas, which lead to an overall decrease in activity, and also due to the fact that ruminating animals ate forced by the nature of their digestive physiology to alternate periods of feeding with periods of rumination, which usually take place while lying down. Well defined high intensity feeding periods were recorded during early morning and late afternoon.

When comparing the different social groups it was found that female herds spend the most time lying down (47,5%). The fact that these herds are exempt from such activities as territorial behaviour, experience limited harassment by terri¬torial bulls and also occupy areas with good grazing (which requires a shorter grazing period), affords them more time to rest. Both male social classes spend more time grazing than do the female herds. For territorial bulls this is largely the result of energy expended through territorial activity, requiring an increased food intake, while bachelor herds usually occu¬py marginal areas with poor grazing and therefore feed for longer periods in order to reach the required nutritional levels. During the dry season an increase in the time spent grazing is evident for all social groups. This tendency is an at¬tempt to compensate for the reduced forage quality normally found during dry periods.

It was established that in areas where hunting often takes place, Wildebeest are more wary and spend less time resting than do animals in non-hunting areas. Evidence also exists that due to hunting, the animals may react to the increased disturbance level by adjusting their activity patterns to become more nocturnal.

Reproduction and related behaviour

Black Wildebeest are strictly seasonal breeders (Von Richter, 1971a). How¬ever, there is variation in the peaks of mating and calving seasons; in general the mating season is from mid-March to the end of April, while the calving season is from mid-November to early January (in the Free State). The gestation period is approximately eight months (average 253 days).

Although thought to have been the exception in the past (Von Richter, 1971a), most females conceive at the age of 16 months and calve when they are two years old. This was established by examining young cows culled on various Provincial nature reserves in the Free State. Similarly, Talbot and Talbot (1963) found that 83% of Blue Wildebeest in Masailand conceive when they are 16 months old. The fact that a large percen¬tage of females calve when they are two years old (i.e. while they are fairly young) makes a considerable difference to the reproductive potential of a Black Wilde¬beest population. For example, at Tus¬sen-die-Riviere Nature Reserve in the sout¬hern Free State, out of a population of 680 animals, 19,2% were sub-adult females (16 months old).

Bulls also reach sexual maturity at. the age of 16 months, but usually first have to secure a territory before being able to mate (bulls become territorial when they are approximately three years old). However, young males were occasionally seen to mate with cows in the presence of a territorial bull. In an experiment con-ducted at the Erfenis Dam Nature Reserve in the central Free State, all adult bulls were removed leaving only young bulls present during the mating season. These bulls mated successfully, but the calving percentage was not as high as normally expected.

Mating behaviour

Territoriality is closely linked to repro¬ductive behaviour and, as mentioned above, possessing a territory is one of the prerequisites for taking part in mating activities. Territorial behaviour, such as the advertising of territories and the performing of challenge rituals (between individual bulls) therefore reach a peak during this period. Besides territorial duties, bulls have to also continuously assess the estrus status of cows.

Female herds move from one terri¬torial bull to another. The time spent with a bull varies considerably and can be from a few hours to a number of days (even weeks). This time depends on the attention afforded them by the bull. Should a bull not pay continual attention to the cows, they move off to another bull. When trying to leave a territory, females are herded by the bull, trying to stop them from leaving. If, however, the females are determined to leave, the bull seldom manages to stop them. Herding varies in intensity depending on the receptiveness of the females in the herd. If there is a female or females in estrus, vigorous herding takes place.

Mating occurs mainly outside the herd or on the periphery of the herd. The reason for this is that the bull usually stands slightly separate from the female herd. A female in estrus normally ap¬proaches the bull and mating takes place. Most mating appears to take place during the late afternoon and at night. It is suspected that cows are in estrus for a few hours only, but that they are bi estrus, a mechanism which ensures that all females are fertilized.

From investigations conducted during the mating season it was evident that the higher the number of bulls in an area, the greater the interaction amongst these bulls. This resulted in less attention being paid to the cows. Consequently, the ge¬neral outcome was a reduced calving percentage. To ensure a higher calving percentage it is therefore advisable to limit the number of bulls in a specific area.

Calving

The majority of Black Wildebeest calves are born within a three week period (Von Richter, 1971b). An identical situation was reported for Blue Wildebeest in East Africa (Estes 1976). Parturition takes place within the herd and this is similar to the findings of Lynch (1974) for Blesbok. Black Wilde¬beest births witnessed were all between 08:00 and 12:00, which is contrary to the findings of Von Richter (op. cit.) who stated that calves were born during early morning, late afternoon and at night. This however, corresponds with the observations of Du Plessis (1968), who re¬ported that for Blesbok, most births oc¬curred in the forenoon. It is perhaps signi¬ficant that late morning coincides with the time of day that most predators are inactive. Although large predators are almost non-existent in areas where Black Wildebeest are found today, this could be a vestige of behaviour important for the survival of these animals in the past.

Unlike most ungulates whose off¬spring remain concealed for some time after birth, e.g. Red Hartebeest, Gemsbok and Steenbok, Black Wildebeest calves accompany their mothers directly after birth (referred to as the follow-up type). In terms of the time needed by a newly-¬born calf to gain its feet and run, Wilde-beest can be considered the most preco¬cious of all known ungulates, a pheno-menon associated with their open habitat and relatively large size and mobility (Lent, 1974: in Estes, 1976).

The early development of the calves is rapid. The first three months are briefly described:

Up to the age of about one month, calves spend the largest part of the day resting (circa 85%). They are suckled re¬gularly by their mothers and the limited grazing observed at this stage takes the form of exploring potential food sources. Calves remain very close to their mothers and are able, if necessary, to keep up with the herd at high speed.

Although a significant reduction in time spent resting is evident during the second month, this activity still accounts for the largest part of the day (circa 55%). A defi¬nite weakening of the mother-calf bond and the forming of creche groups is noti¬ceable. However, when danger threatens, calves remain inseparable from their mothers. An increase in grazing activity can also be seen, although the calves still suckle regularly.

During the third month resting still oc¬cupies the largest part of the day (circa 54%), but there is a significant increase in the time spent grazing, as the calves progress towards weaning. Creche beha¬viour is more pronounced during this period, with calves spending most of the day together.

Recommended sex ratios

Von Richter (1971b) recommended that a desirable sex ratio for stocking should be one adult male to 13 adult females. However, suggesting a specific sex ratio and predicting certain results is difficult, as various factors can play a role, e.g. the ages of the animals, the condition of the veld, the size of the game farm, etc.

The numbers and sex ratios of Black Wildebeest that were re-introduced into one of the smaller nature reserves in the central Free State can be used as a practical example and as a possible guideline. In 1971, twelve Black Wilde¬beest (2 bulls and 10 cows - ages unknown) were released in the Erfenis Dam Nature Reserve, which has approximate¬ly 500 ha of typical grassveld. By 1979 there were 101 Black Wildebeest in the area, this after removing 26 animals (11 in 1976 and 15 in 1978). Since 1980, Black Wildebeest have been taken off annually and by the end of 1990 a total of 365 animals had been removed. At the beginning of 1991 there were 40 Black Wildebeest on the reserve. No signs of inbreeding have been evident and trophy quality Black Wildebeest are common in this reserve.

Hybridization (Cross-breeding)

According to the “Species Listing” process, within the framework of the National Environmental Management Act 2004, it has been proposed that the Black Wildebeest be listed as a “Protected” species, this is mainly because of the threat posed by hybridization with the closely related Blue Wildebeest (Connochaetes taurinus); although the natural distribution range of these two species is known to have overlapped in historical times, there is no recorded evidence that there was hybridization during this period. However, the confinement of the two species together in protected areas and on private farmland in recent times, has, in some cases, resulted in hybridization.

The occurrence of Black x Blue Wildebeest hybrids (cross-breeds) was first reported in KwaZulu-Natal in the early sixties. Of major concern is the fact that hybrids are fertile. First generation hybrids are easily identified, but the offspring of hybrids that have interbred with pure stock Black Wildebeest are difficult to recognize on appearance alone. The external appearance of hybrids varies, with the most obvious feature being the shape of the horns.

Previously it was believed that hybridization only occurs under artificial conditions, where males of the one species and females of the other species are forced together in a confined area. However, it was later established that crossbreeding can occur wherever Black and Blue Wildebeest are kept together, irrespective of the area involved. During the year 2000, in a 6 000 ha nature reserve housing large herds of both species, hybridization did occur and all of the animals had to be destroyed. Hybridization is primarily due to the similar behaviour and the synchronized breeding seasons of the two species. As most recorded instances of hybridization have been of Blue Wildebeest males crossbreeding with Black Wildebeest females, it is thought that this could be due to the larger sized Blue Wildebeest bulls displacing the Black Wildebeest bulls.

Implications

Presently, with the large-scale increase in the number of game ranches being developed throughout South Africa, landowners are keeping a wider range of species on their properties, primarily to cater for local and overseas hunters, and resulting in more and more farms housing both Wildebeest species together. This has led to several confirmed cases of hybridization in some provinces, and the genetic integrity of especially the Black Wildebeest is being threatened by this activity.

While the extensive distribution that the Blue Wildebeest has in Africa means that this species is not similarly threatened, the genetic integrity of the South African populations are at risk, a threat that could seriously impact on the credibility of the local hunting industry.

The extent of the crossbreeding throughout South Africa is not presently known, however, the hunting fraternity is reporting more and more cases of hybridization in different parts of the country. Black Wildebeest numbers are still relatively low in South Africa and therefore the risk of extinction remains very real. It goes without saying that this would also have serious economic implications on the value of both these species. In order to remedy this unacceptable situation, it is of utmost importance to impose drastic measures, on a national level, to address this serious problem.

National Initiative

A national project, involving all provinces and other role-players, aimed at investigating the extent of hybridization and the development of a national policy and strategy to ensure the genetic integrity of both these species, has been initiated. This project will include genetic and osteological testing of samples from both species, the former being required to assist with the identification of backcrosses of hybrids with Black Wildebeest. Funding for this project still needs to be sourced.

References

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