R. R. HOFMANN / D. R. M. STEWART

GRAZER OR BROWSER: A CLASSIFICATION BASED ON THE STOMACH-STRUCTURE AND FEEDING HABITS OF EAST AFRICAN RUMINANTS

R. R. HOFMANN / D. R. M. STEWART

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Citation Information: Mammalia. Volume 36, Issue 2, Pages 226–240, ISSN (Online) 1864-1547, ISSN (Print) 0025-1461, DOI: 10.1515/mamm.1972.36.2.226, October 2009

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Cade, C. E. (1966)

Cade, C. E. (1966), A NOTE ON THE MATING BEHAVIOUR OF THE KENYA ORIBI Ourebia ourebi IN CAPTIVITY. International Zoo Yearbook, 6: 205. doi:10.1111/j.1748-1090.1966.tb01757.x

MDUMA, S. A.R. and SINCLAIR, A. R. E. (1994)

Summary

A study of habitat selection by oribi (Ourebia ourebi, Zimmermann 1783), a small antelope in northern Serengeti National Park, Tanzania, addressed two questions:

(1) what were the most preferred habitat features? and

(2) did oribi associate with or avoid other ungulates?

These questions were pertinent to three hypotheses on the function of habitat selection in antelopes: (i) habitats are chosen to minimize the cost of obtaining resources, (ii) habitat selection results from niche partitioning due to interspecific competition, or (iii) habitat selection functions to avoid predation by using escape terrain and by associating with other species for protection. Results from transects designed to examine preferences for open grassland, Acacia woodlands, Combretum-Terminalia woodland, forests, thickets and rocky habitat types suggested that oribi preferred habitats with rocky outcrops and Combretum-Terminalia woodland.

These habitats supported preferred food plant species consistent with hypothesis (i). However, oribi occurred close to rocks in the dry season, and in areas with long grass during the wet season, both of which are used for cover against predators. The significant association of oribi with larger resident ungulates [impala (Aepyceros melampus) and kongoni (Alcelaphus buselaphus)] also suggested that oribi were avoiding predators, consistent with hypothesis (iii). Oribi avoided wildebeest, possibly because of interference, but were randomly associated with topi, zebra and Thomson's gazelle.

Preference for plateaux or gentle slopes and green flush agree with studies elsewhere. Major contrasts were shown in the avoidance of open grasslands and Themeda triandra which are reported to be favoured by most oribi populations in South Africa. 

MDUMA, S. A.R. and SINCLAIR, A. R. E. (1994), The function of habitat selection by oribi in Serengeti, Tanzania. African Journal of Ecology, 32: 16–29. doi:10.1111/j.1365-2028.1994.tb00551.x

JONGEJAN, G., ARCESE, P. and SINCLAIR, A. R. E. (1991)

Summary

This paper describes observations on body size, growth, and the timing of births in an individually identified population of oribi (Ourebia ourebi, Zimmermann 1783) in the Serengeti National Park, Tanzania. Females tended to be larger and approximately 2 kg heavier than males. Young oribi grew rapidly, attaining near-adult size in about 7 months. Horns appeared in male oribi at about 4½ months of age and grew rapidly up to 20 months of age. Births occurred in all months of the year but were most common between March and June. The results provide an observational means of estimating the age of sub-adult oribi by body size, and the age of adult male oribi, up to 20 months of age, by horn length.

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JONGEJAN, G., ARCESE, P. and SINCLAIR, A. R. E. (1991), Growth, size and the timing of births in an individually identified population of oribi. African Journal of Ecology, 29: 340–352. doi:10.1111/j.1365-2028.1991.tb00471.x

Arcese, P., Jongejan, G. and Sinclair, A. R. E. (1995)

Behavioural Flexibility in a Small African Antelope: Group Size and Composition in the Oribi (Ourebia ourebi, Bovidae)

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Department of Wildlife Ecology, University of Wisconsin, Madison, WI 53706, USA.

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Abstract

Individually identified Ourebia ourebi (Bovidae) were observed in Serengeti National Park for 1–8 mo, annually, from 1987 to 1993 to study flexibility in the size and composition of territorial groups. A total of 236 O. ourebi were re-sighted over periods of 1 yr or more. The modal number of adults in groups was three in all years (range: 1–7; x̄ = 3.1, SE = 0.2, n = 5 yr; 136 groups overall); maximum group size with adolescent young and calves was eight. In 32% of 136 identified groups, two adult males were resident for at least 1 yr, as were three adult males in 4% of all groups. Groups with up to three adult females were common (range: 0–5). Overall, 25% of 32 adult males and 27% of 26 adult females were still present on the territory where first identified after 4 yr. Only 14% of 35 male-female dyads remained intact over the same period. O. ourebi in Serengeti appear to be primarily polygynous, with a moderate rate of yr-to-yr residency in particular groups, and with a low rate of long-term pairing between males and females. Groups with more than one adult male are not unique to Serengeti but their significance has not been previously considered. Comparisons across O. ourebi populations in Africa show that polygyny is positively correlated with the ratio of adult females to males, population density, mean group size, and the prevalence of multi-male groups, but there is less evidence that these variables influence the number of adult males in groups. Experiments are required to determine how demography, predation pressure, and the quality and distribution of food influence group size and composition in O. ourebi and other small antelope.

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cite: Arcese, P., Jongejan, G. and Sinclair, A. R. E. (1995), Behavioural Flexibility in a Small African Antelope: Group Size and Composition in the Oribi (Ourebia ourebi, Bovidae). Ethology, 99: 1–23. doi:10.1111/j.1439-0310.1995.tb01085.x

Peter Arcese

Department of Wildlife Ecology, University of Wisconsin, Madison, WI 53706-1598, U.S.A.

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The evolution of horns in male ungulates is thought to occur primarily via sexual selection and male competition, thus horns are considered to have evolved principally for their value as weapons. 

However, experiments have shown that female birds sometimes prefer males with extreme phenotypes and low levels of bilateral symmetry in sexual ornaments.  Therefore, it is plausible that the evolution of horn size and shape in male ungulates is also affected by female preference.  I show that harem size in Oribi is related to horn symmetry in males.  This might result in females prefer males with symmetric horns or other traits correlated with horn shape, such as territory quality.

Theory predicts that only the best males will produce large ornaments when these are costly to grow and carry.  I therefore expected that male oribi with the longest horns would have the most mates.

In addition, because horns are bilaterally symmetric in oribi, fluctuating asymmetry in horn shape may indicate genetic vigour.

Thus, at the outset of data analysis, I predicted that females should prefer males with symmetrically shaped horns versus developmentally asymmetric horns or those showing asymmetry due to damage.

I also tested whether horn length were a cue to male quality.

Oribi are small antelope that live in groups of 2 to 7 adults on territories year-round.

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Harem size was defined as the mean annual number of mature females on a male's territory over all years he was present and was approximately normally distributed.  Further details of methods and oribi structure are given in Arcese et al.  (in press).

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Male oribi typically have short (ca 12- 16cm), straight horns; but variation exists because horns, grow and wear, and because the orientation of each horn with respect to the other varies among males.  Horn length was estimated visually in relation to the ear and was highly correlated to actual lengths measured on immobilized males.  Horn shape was also determined visually when a male was first sighted.  To do so, another observer and I compared each male to a 'standard'of 2 vertical horns that were spaced so that they were as wide at the top as the base.

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By discussing our observations and re-checking the male, we determined whether the horns differed sufficiently in shape from the standard that we judged the difference useful for re-identification.

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If so, we classified it as one of the 7 stereotyped variants.

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Adamczak VG., Dunbar RIM.

Flexibility (varying from monogamy in South Africa to polygyny in East Africa) has been documented in the mating system of the oribi (Ourebia ourebi) by several authors. To investigate this, a population was studied in Northern KwaZulu-Natal (South Africa). The adult sex ratio was one male to 1.38 females and the mean group size was 2.1 (n = 13). Although monogamous and polygynous groups occurred in the study population, the polygynous groups were unstable and depended on seasonal food abundance. Comparison of oribi populations across Africa suggests that variation in the mating system is determined mainly by predation risk and altitude (most likely through its effect on graze quality). In areas of high predation risk, oribi can survive only when resource quality permits females to forage in groups, thereby allowing males to be polygynous

D.T. Rowe-Rowe, P.S. Everett & M.R. Perrin

Data collected on group sizes of the oribi Ourebia ourebi at midland elevations in Natal, South Africa, were compared with available data from montane (Drakensberg) and tropical (East Africa) grasslands. Mean group sizes were lowest in montane grassland and highest in tropical grassland. In the montane areas adults occurred mainly in pairs or as single animals, whereas small harem herds predominated in tropical grassland, while the organization at midland areas was intermediate. It is suggested that the social organization of the oribi is influenced by habitat suitability, and availability and quality of food during winter. This hypothesis is discussed in relation to the three areas considered.

Our conclusion is that adult oribis in the Drakensberg occur singly or in pairs, strongly resembling the composition of Jarman's (1974) Class A. In the tropical grasslands of East Africa small harem herds are formed, typical of Jarman's (1974) Class B, generally consisting of three to six animals. The social organization in the midland areas of Natal is intermediate between Classes A and B, with roughly 30% of the groups containing more than one adult female. We believe that these differences are probably related to habitat suitability, and availability and quality of food. In S.-Afr. Tydskr. Dierk. 1992, 27(3) the less suitable habitats oribis need to be in more widely dispersed, and occur at lower densities to ensure that their nutritional requirements are satisfied.

Peter Arcese, Gwen Jongejan, A.R.E. Sinclair 1995

Individually identified Ourebia ourebi (Bovidae) were observed in Serengeti National Park for 1–8 mo, annually, from 1987 to 1993 to study flexibility in the size and composition of territorial groups. A total of 236 O. ourebi were resighted over periods of 1 yr or more. The modal number of adults in groups was three in all years (range: 1–7; x̄ = 3.1, SE = 0.2, n = 5 yr; 136 groups overall); maximum group size with adolescent young and calves was eight. In 32% of 136 identified groups, two adult males were resident for at least 1 yr, as were three adult males in 4% of all groups. Groups with up to three adult females were common (range: 0–5). Overall, 25% of 32 adult males and 27% of 26 adult females were still present on the territory where first identified after 4 yr. Only 14% of 35 male-female dyads remained intact over the same period. O. ourebi in Serengeti appear to be primarily polygynous, with a moderate rate of yr-to-yr residency in particular groups, and with a low rate of long-term pairing between males and females. Groups with more than one adult male are not unique to Serengeti but their significance has not been previously considered. Comparisons across O. ourebipopulations in Africa show that polygyny is positively correlated with the ratio of adult females to males, population density, mean group size, and the prevalence of multi-male groups, but there is less evidence that these variables influence the number of adult males in groups. Experiments are required to determine how demography, predation pressure, and the quality and distribution of food influence group size and composition in O. ourebi and other small antelope.

C. R. Goldspink, R. K. Holland, G. Sweet, L. Stewart

The oribi (Ourebia ourebi, Zimmermann, 1783) is a small species of antelope widely represented across open grasslands of sub-Saharan Africa. Although largely territorial, differences in group size and mating systems (monogamy/polygamy), have been linked to habitat conditions and population density. At high population densities, additional males are recruited to assist in territorial defence. Other factors which might impact on group size, include predation threat, especially at low population densities. In this study (1995–98), we recorded group sizes of oribi across two contrasting areas (c. 300 km2 each) of Zambia with (Kafue), and without (Bangweulu), large vertebrate predators. A total of 412 groups was recorded across the two sites, with mean sizes of 2.31 (n = 217) at Bangweulu and 2.33 (n = 195) at Kafue. The modal group size was two throughout (range 1–6). Groups were more variable in size and sex composition at Kafue than at Bangweulu, but there was no significant difference in estimates of population density between sites. Mean estimates were 2.02 and 1.90 km−2 for Bangweulu and Kafue, respectively. Sex ratios (males : females) were biased towards females (1 : 1.72 and 1 : 3.55, respectively) at both sites. Adult males were particularly scarce at Kafue. However, values of density and group size, were both unexceptional for the species. Whilst a modal group size of two is consistent with a monogamous mating system, variations in group composition and size were more difficult to explain. Adult females appeared to retain or recruit additional animals to groups, irrespective of the needs of territorial defence. This suggests that vigilance is an important function of groups on large open plains, especially in the presence of predators. By extension, reversed sexual dimorphism in oribi could reflect increased selection for vigilance duties in females. Predators had no apparent effect on population density, but oribi groups were more variable in size and sex composition in their presence. Adult males may be particularly vulnerable to predation when defending territorial borders at low population densities. However, further work is needed to define group dynamics in this species and to identify causes of mortality amongst adult males.

Oliver MDN, Short NRM, Hanks J 1978

Populations of oribi, grey rhebuck and mountain reedbuck in Highmoor State Forest Land experienced seasonal population fluctuations that were unrelated to jackal predation. All three antelope species had a peak in deaths during the winter months, and it is possible that winter malnutrition is a major population-limiting factor. In oribi, the sex ratio did not depart significantly from unity, but in both grey rhebuck and mountain reedbuck the ratio was very significantly biased in favour of females. Both grey rhebuck and oribi had a significant peak of births in the summer months, whereas mountain reedbuck bred throughout the year. Mountain reedbuck favoured the steeper valley sides with their scattered Pro tea tree-veld and avoided the plateau area occupied by oribi and grey rhebuck. The overall standing crop of all three species was very low when compared with the estimated potential carrying capacity for wild ungulates in highland sourveld. Home range estimates were made for oribi and grey rhebuck, and all three species were compared on both crude and ecological density basis. Provisional observations on social organization suggest that all three species may be territorial.

Wondimagegnehu Tekalign, Afework Bekele

Studies on sex structure and group size of oribi (Ourebia ourebi) were carried out in the newly established Maze National Park, Southern Nations Nationalities and People’s Regional State, Ethiopia, during the wet and dry seasons from October 2009 to February 2012. A total count method was employed to determine the sex and age structure based on silent detection in an area of 220 km2 . The area was divided into eight counting blocks based on natural and artificial boundaries. The ratio of adult males to adult females ranged from 1:1.30 to 1:1.48 and 1:1.25 to 1:1.33 during wet and dry seasons of the study years, respectively. There were more adult females than adult males and young. Group size varied from lone individual to the upper limit of 13 and 19 during the wet and dry seasons, respectively. The largest group was found in the short grasslands and the smallest within woodland and long grasses. Many of the individuals were observed in pairs with a large number of adult male and female couples. Proper and urgent measures should be taken to limit illegal activities to conserve the wildlife of the area.

B.K. Reilly, G.K. Theron, J. du P. Bothma

During a two-year study on the ecology of oribi Ourebia ourebi (Zimmermann, 1783) in the Golden Gate Highlands National Park, plant species fed on by oribi were noted. The oribi fed on a total of 22 plant species. Feeding preference categories were assigned according to the degree of use of different plant species, based on direct observation and on a preference rating. The oribi in the Golden Gate Highlands National Park showed a seasonal variation in feeding preferences, utilising several species of forbs primarily during the summer and a marked dif-ference between per cent frequency utilisation of plant species and actual preference rating according to availability of species and for certain plant parts, e.g. for Sporobolus centrifugus.

Wondimagegnehu Tekalign, Afework Bekele

The study on the population status, foraging behaviour and diurnal activity pattern of oribi (Ourebia ourebi) was carried out in Senkele Swayne’s Hartebeest Sanctuary from August 2005 to March 2006 during the wet and dry seasons. Direct observation on selected oribi groups was made to study activity patterns. Total count method was used in an area of 28 km2. The count of oribi in the study area ranged between 45 and 57 during the wet and dry seasons, respectively. There was no significant difference between the wet and dry season count (p>0.05). The sex ratio of adult males to females was 1.00:1.26. Oribi were mostly observed as solitary or in pairs, occasionally forming small groups. Oribi distribution showed preference to grazing on short grass (Themeda triandra) in each vegetation community. The distribution of oribi during the wet and dry seasons was similar in all vegetation communities. However, the tendency of population for wider distribution increased in the Pennisetumgrassland. The annual mean proportion of daylight hours spent feeding by oribi was 54.7%. Morning and evening activity peaks were most obvious during the dry season, with most animals remaining inactive during the midday and hottest hours of the day. Large number of settled human communities in and around the Sanctuary and herds of livestock were frequently observed mainly during the wet season. Overgrazing and settlement encroachment are the major factors that could affect the population status of oribi by lowering the grass quality in the Sanctuary.

Wondimagegnehu Tekalign, Afework Bekele

Abstract Habitat association and foraging ecology of oribi (Ourebia ourebi) were carried out in the Maze National Park, Ethiopia, during the wet and dry seasons from October 2009 to December 2012. The type of habitat where the animals frequented and the food consumed were recorded for each season. Four habitat types were identified based on the vegetation. Eight variable sized blocks were designed based on the natural and artificial boundaries. Foraging records were carried out during active feeding period of oribi to observe the plant species that were consumed. Focal animals were chosen and observed. The distribution of oribi was high (64.17% and 69.32%) in the grassland with scattered trees and low in bushland (8.37% and 4.46%) habitat types during both wet and dry seasons, respectively. Seasonal distribution of individuals among the habitats was significant (p<0.05). Some oribi were observed moving out to nearby villages and farmlands. Oribi were more associated with livestock and Swayne's hartebeests than other animals. They fed on a total of 28 plant species in the Park area. Andropogon gayanus and Themeda triandra were the most preferred and utilized grass species. It is important to improve both the quality and the quantity of forage availability within the Park by adopting a more effective vegetation management program based on controlled burning. Keywords: Distribution, Habitat, Feeding, Maze National Park, Oribi

Andrew Hill

Geographic information systems and remotely sensed information provide an analytical platform for linking habitat features and animal distribution in a spatial context. The spatial culmination of such data using geographic information systems technologies is an important step towards providing information to decision makers on habitat suitability and the mapping thereof. Through the use of such techniques, environmental factors indicative of suitable habitat of the endangered oribi antelope were mapped within the extent of KwaZulu-Natal. The factors and individual weights were identified through multi criteria evaluation using analytical hierarchical process and expert knowledge. The resultant suitability indexed model provided a basis for cost distance procedures and was used to identify potential habitat corridors. An oribi conservation area network was created using these potential corridors and further cost distance functions. The Karkloof and Chelmsford conservation area networks reported the greatest concentrations of highly suitable habitat and therefore with reference to oribi specific habitat recommendations, draft management recommendations were collated.

Keenan Stears

Key factors driving the foraging ecology of Oribi:  Fear, Cattle and the Quality and Quantity of Food

Tamanna Patel

Population Dynamics and Relocation Success of the Oribi Antelope (Ourebia ourebi) in KwaZulu-Natal, South Africa

Rebecca Grey-Ross, Colleen T Downs, Kevin P Kirkman

In South Africa, the oribi, Ourebia ourebi is an endangered small antelope that requires conservation management and intervention to prevent their extinction. Use of translocation for the conservation of subpopulations facing local extinction in the wild has been proposed. In this study, fifteen oribi from threatened populations were captured and released (November 2004) on a private game reserve in KwaZulu-Natal, South Africa. Radio telemetry was used to monitor the dispersal and survival of translocated oribi. Only one death occurred during that period. All other released oribi survived, and most remained in close proximity of the release site for more than a year postrelease. Reproduction also occurred. This suggests that, translocation could be a viable option for conserving wild populations of oribi, assuming that other factors, such as availability of suitable grassland habitat and that poaching has been curtailed, are met.

Rebecca Grey-Ross, Colleen T Downs, Kevin P Kirkman

Oribi (Ourebia ourebi) are listed as endangered and one of the options to increase their numbers and populations is to breed them in captivity and subsequently reintroduce them into suitable habitat. A captive breeding facility for oribi in KwaZulu-Natal, South Africa, had been used to reintroduce captive-bred oribi on to the neighbouring agricultural/game farm for the previous 10 years. However, the success of these reintroductions was unknown. Consequently the aim of this study was to monitor the success of the reintroduction of captive-bred oribi. As in previous years, 10 captive-bred oribi were released by the owners of the facility onto the neighbouring farm. Using radio-telemetry and mortality sensors, survivorship of the reintroduced oribi was monitored, and the factors involved in a successful or failed reintroduction attempt Identified. Within two months of release, seven of the 10 oribi were dead. The causes of mortality varied, but predation by natural predators and humans was a major factor. Consequently no further reintroductions on to this property were advised. Several factors of concern were raised and need to be addressed in future captive breeding, reintroduction and management of oribi.

Rebecca Grey-Ross, Colleen T Downs, Kevin P Kirkman

Increasing transformation and fragmentation of rural landscapes for economic reasons is causing concern to conservationists worldwide. With this trend likely to continue, perhaps conservation agencies and development corporations need to co-operate and plan housing developments that are environmentally and ecologically sustainable and can serve as refuges for endangered species. In KwaZulu-Natal, South Africa, grasslands are particularly threatened by land transformation for housing developments. A case study is presented of a housing development, Wedgewood Estate in KwaZulu-Natal that has been developed and managed for conserving grassland habitat and associated species, particularly the endangered oribi (Ourebia ourebi). Feedback from the Estate's managers about the development and ecological impact were obtained. Wedgewood is an example of the viability of housing estates as refuges for endangered species and shows that the density and placement of housing and management of the natural habitat are important. It emphasizes the need for reviewing the types and amount of housing development, management of natural habitat, and the rules and regulations they put in place to assure the integrity of the conservancy is preserved. This case study also shows the potential of such ecologically sensitive housing developments as sources of surplus game for translocation, especially in the case of endangered species such as oribi.

Taylor, W.A., Lindsey, P.A. & Davies-Mostert, H. 2015.

An assessment of the economic, social and conservation value of the wildlife ranching industry and its potential to support the green economy in South Africa. The Endangered Wildlife Trust, Johannesburg.

Liesel L. Laubscher1 *, Neville E. Pitts2 , Jacobus P. Raath3 & Louwrens C. Hoffman1

Annually, thousands of game animals are captured and relocated across South Africa. One of the biggest causes of mortality during these translocations is stress, and as such it is the responsibility of all stakeholders involved to ensure that appropriate techniques are applied for specific species and environments. It is therefore important that there is a thorough understanding of these methods not only from a management perspective but also in terms of applied animal welfare. This review provides detailed descriptions of the various non-chemical techniques that may be employed during game capture and relocation in a South African context and highlights both species suitability, as well as the advantages and disadvantages of each technique. It also gives a brief background to the South African game capture industry as well as discussing and giving guidelines for the transportation and holding of wildlife after capture.

Grey, Rebecca Victoria. 2006

Aspects of the conservation of oribi (Ourebia ourebi) in KwaZulu-Natal.   

As a specialist grazer, it is extremely susceptible to habitat loss and the
transformation of habitat by development. Another major threat to this species is
illegal hunting.

Captive breeding programmes, reintroduction of captive-bred individuals to wild populations.

D T Rowe-Rowe

Wildlife Management - Habitat preference of game mammals

Young Event

Overstraining disease in tsessebe and oribi is described for the first time. Reference is made to the symptomatology, pathology and treatment of this very important syndrome in the mentioned species