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Reproductive seasonality in the female scimitar-horned oryx (Oryx dammah)

  • C. J. Morrow (a1) (a2), D. E. Wildt (a1) and S. L. Monfort (a1)

Abstract

Faecal oestrogen and progestin analyses were used to assess ovarian activity in non-pregnant scimitar-horned oryx (Oryx dammah) during a 13-month interval. Mean (± SE) luteal phase, interluteal phase and oestrous cycle duration were 18.8 (± 0.5), 5.1 (± 0.2) and 23.8 (± 1.3) days, respectively. All females exhibited a synchronized anovulatory period that ranged from 36–95 days during spring. Short ovarian cycles (10.6 (± 0.8) days) were observed intermittently throughout the year and before the spontaneous resumption of oestrous cyclicity. Periovulatory peaks in oestrogen concentrations were detected for 42.5% (31/73) of ovarian cycles. A parallel analysis of reproductive data from the North American studbook (1985–1994) revealed that captive-held scimitar-horned oryx gave birth throughout the year. Sex ratio at birth was male-biased (54.4%), and 19.1% of all calves failed to survive to 6 months of age (220 out of 1149 births). Only 0.7% of births resulted in twins. Median interbirth interval was 277 days, and 75% of these intervals were less than 332 days. Interbirth interval was extended (P < 0.05) if parturition occurred from January through May. In summary, the scimitar-horned oryx is a seasonally polyoestrous species that experiences a distinct anovulatory period during spring in north-east America.

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AgResearch, Ruakura Agricultural Centre, Private Bag 3123, Hamilton, New Zealand. Tel: 64 7 838 5574; Fax: 64 7 838 5727; E-mail: morrowc@agresearch.cri.nz.
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Reproductive seasonality in the female scimitar-horned oryx (Oryx dammah)

  • C. J. Morrow (a1) (a2), D. E. Wildt (a1) and S. L. Monfort (a1)

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