The Biology, Husbandry and Conservation Scimitar-horned Oryx ...

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21 Part 2: Husbandry Guidelines 8 Social Organisation of Scimitar-horned Oryx in Captivity JUERGEN ENGEL The social organisation of captive ungulates is dictated by the institutions in which they are held. This section reviews the various social systems for managing herd animals with special reference to available knowledge on the social behaviour of scimitar-horned oryx prior to extinction in the wild (section 3) and experiences gained from maintaining the species in zoos (appendix F). As scimitar-horned oryx are gregarious in nature, I begin by discussing the various ways in which a herd may be constituted. Thereafter, I address questions regarding the formation of bachelor groups, and managing animals in pairs or singly. Herds One male, several females (harem group) Harem groups, consisting of a dominant male, several females and their offspring is the most common system for managing scimitar-horned oryx in zoos throughout the world, and is recommended by previous authors writing on the subject (Kock and Hawkey, 1988; Puschmann, 1989). An important issue is the timing of the removal of young males from the breeding herd. Male scimitar-horned oryx become sexually mature at ten to 22 (maximum 30) months of age (Dittrich, 1970, 1972; Newby, 1974; Gill & Cave-Browne, 1988; Wakefield 1993b; Volf, 1994). However, to breed successfully, males have to be dominant over their mate, and they are unlikely to exert dominance over all females until they are four years old (Engel, 1997a). Observations made at Paris Zoo suggest that some young oryx (less than four years old) will mate with females, but this tends to depend on the rank of the female concerned (C. Renvoise, pers comm.). Males facing competition with other among multi-male breeding groups (see below) will not reproduce until 28 to 42 months of age (Nishiki, 1992). Therefore, if the enclosure is sufficiently large and well structured, young males do not need be removed from the breeding herd (if ever) until they are two years old at the earliest. As there is an almost balanced sex ratio at birth in the captive population with an equal number of male and female scimitar-horned oryx, the question remains what to do with the surplus male animals. Possible solutions, including groups with more than one adult male or bachelor groups are discussed below. Several males, one female This grouping is definitely not recommended, as every adult male will try to monopolise the female. Consequently, there will be a large number of severe aggressive encounters between the males and a lot of distress caused for the female, which will be permanently herded, courted or mated without any time for rest.
22 Part 2: Husbandry Guidelines Several males, several females (multi-male group) In the wild, scimitar-horned oryx formed groups with an almost equal sex ratio of 1:1 (Newby, 1974; Estes, 1974, 1991a, 1991b; Kranz & Ralls, 1979; Macdonald, 1984; IUCN, 1987; Stanley Price, 1989; Gordon, 1991). In contrast, zoo animals are almost exclusively kept in one-male to several females groups with only a few institutions going against this convention by keeping several males and females in the same herd. Essential requirements for this type of group are a large and well-structured enclosure, as well as one male whose dominant position is unchallenged. The latter is easily accomplished if the prime male is considerably older (though not senile) than the other males. The subdominant males will form a subgroup within the herd, but not an independent bachelor group (Engel, 1997a). Problems will occur when there is only one other adult male in addition to the dominant breeding male. If there are several bachelors, the attention of the alpha male is not focused on a single competitor. As a result, there are no long-lasting agonistic interactions and the whole group is much more stable. If a specific male is recommended for breeding, the other males have to be removed from the group for about one month. On their return, the breeding male will prevent them from getting close to any females in oestrus. If a bachelor tries to usurp the dominant male when returned to the herd, he should be removed from the group for another two to three weeks. This should protect the alpha position of the desired breeding male (S. McKeown, pers. comm.). Single sex groups: several males (bachelor group) All male or bachelor groups were not recorded in wild scimitar-horned oryx, but are a common phenomenon in ungulates. Engel (1997a) addressed this question for scimitar-horned oryx statistically by comparing the social systems of 147 bovid (sub-) species. The study concluded that there was a high probability (99.75%) that all-male groups of scimitar-horned oryx would occur naturally. Moreover, bachelor groups can be expected to include males of varying ages and to be formed throughout the year. Bachelor groups of scimitar-horned oryx have been formed in zoos with varying degrees of success. However, this approach may offer a viable solution to problems of surplus males and opportunities for their social development provided lessons from previous experiences are taken into consideration. According to Engel (1997a), 60% of zoos maintaining scimitar-horned oryx bachelor groups, experienced problems including aggressive interactions between animals that resulted in death. In other cases, individuals had to be separated with many males losing one or both of their horns. Horn loss presents a problem if an individual is needed for breeding at a later date because females will not tolerate males that are unable to become dominant in the herd. The Fossil Rim Wildlife Center in Texas has attempted to control aggression in bachelor groups with the aid of hormonal implants (Blumer et al., 1992). Similar experiments using a synthetic progestogen given with feed were carried out with all-male groups of fringe-eared oryx Oryx gazella callotis at the San Diego Wild Animal Park (Patton et al., 2001). All treatments successfully reduced aggression for some time, but little is known about possible side effects or long-term impacts. Consequently, it is uncertain if medication is really a practical solution for the problem. In some cases, castration of the most aggressive animals has led to a
Page 1 and 2: The Biology, Husbandry and Conserva
Page 3 and 4: Acknowledgements We would like to t
Page 5 and 6: Contents Acknowledgements i Forewor
Page 7 and 8: 1 Taxonomy & Nomenclature JUERGEN E
Page 9 and 10: 2 Morphology & Genetics JUERGEN ENG
Page 11 and 12: 5 Part 1: Biology & Conservation 19
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Page 15 and 16: Table 1. Continued… Group Species
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Page 35 and 36: 10 Zoo Diet & Nutrition TANIA GILBE
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Page 45 and 46: 13 Transport RENATA MOLCANOVA & TAN
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Page 53 and 54: 15 Veterinary guidelines EDMUND FLA
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Page 61 and 62: Bibliography 54 Bibliography Abaiga
Page 63 and 64: 56 Bibliography Bush, M. & Custer,
Page 65 and 66: 58 Bibliography Estes, R.D. (1991a)
Page 67 and 68: 60 Bibliography Gosling, L.M. (1974
Page 69 and 70: 62 Bibliography Krebs, J.R. & Davie
Page 71 and 72: 64 Bibliography Newby, J.E. (1981b)
Page 73 and 74: 66 Bibliography Roth, T.L., William
Page 75 and 76: 68 Bibliography Wakefield, S. (1993
Page 77 and 78: 70 Appendices were also interrelate
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72 Appendices APPENDIX B The Reintr
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Appendices After the herd was mixed
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76 Appendices This relates to a juv
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78 Appendices 3. Reintroducing the
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80 Appendices national park had def
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Appendices APPENDIX D The Reintrodu
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Appendices APPENDIX E Other Conserv
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86 Appendices APPENDIX F Captive an
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88 Appendices • herding (male tri
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90 Appendices APPENDIX H Nutritiona
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Table I1. continued… Variable Uni
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Hans-Peter Muller 3 Rue Maarif 1000
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