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With 2 figures in the text)Behavioural observations of both captive and free-ranging sand and mountain gazelles revealed differences in group size and composition, territory size and agonistic behaviour. Sand gazelles are seasonal breeders and form large herds (maximum = 56) during rut and post-rut as compared to mountain gazelles, which breed throughout the year in smaller groups (maximum= 5). As a result, mountain gazelle males maintain their territories year round, whereas sand gazelle rams show marked morphological changes and defend a territory only during the rut. Mountain gazelle males exhibited threat displays rather than engaging in actual combat more often than did sand gazelles. Although subject to the same environmental conditions, sand gazelles are seasonal breeders and the young are born in March-April, whereas mountain gazelles give birth throughout the year.

Despite increased hunting pressure accompanied by habitat degradation, the current distribution of Nubian ibex Capra ibex nubiana in Saudi Arabia closely resembles that of historical record and spans a wide diversity of habitat types. Efforts are under way to conserve the species and two special ibex reserves have been created.

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With 3 figures in the text)Group dynamics of the Nubian ibex (Cupru ibex nubiunaj, a sub-species adapted to arid environments, were studied at the Ibex Reserve, Saudi Arabia. Most of the animals (83%) were seen in mixed herds during the rut and post-rut. Mean group size of all sex-age categories was 7.2, with the majority of the ibex seen in groups of < 10. The sex ratio of adult animals was equal but that of juveniles, older than six months, was skewed towards females. Habitat structure, sparse vegetation cover and a small population size are factors that favour small group size. An equal adult sex ratio and a high number of juveniles indicate that the population has a high reproductive potential.