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Social system variability in a population of reintroduced Arabian oryx Oryx leucoryx in Oman was investigated from 1982 to 1989 by comparing two time periods on either side of June 1986, when widespread rain ended a prolonged period of drought and supplemental feeding. Variation in three social subsystems of resource exploitation, mating, and calf-rearing were observed. From the first release of 10 oryx in 1982 until June 1986, median herd size increased over time, while average group size increased as forage conditions deteriorated after rain. In addition, within each herd subordinate adult males were tolerated by dominant males, only a few dominant males sired the majority of calves, and the proportion of mother/calf pairs involving older, weaned calves progressively increased. After June 1986 until the end of the study period in December 1989, these trends reversed. Median herd size decreased over time, and average group size decreased as forage conditions deteriorated after rain. Subordinate adult males were no longer tolerated within herds, but instead existed as solitary males. The concurrent increase in solitary males and the number of herds resulted in more breeding opportunities for the expanding adult male population. The mating system became more dynamic, and involved the emergence of previously unrecorded territorial behaviors. In addition, the proportion of mother/calf pairs including weaned calves decreased. As the transition from captivity to the wild may present special difficulties in the development of social systems specifically suited to local conditions, species with more adaptable social systems, such as the oryx, are likely better candidates for reintroduction. |
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