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The influence of rainfall on range in a female desert ungulate: the Arabian oryx (Oryx leucoryx) in the Sultanate of Oman

Published online by Cambridge University Press:  27 February 2001

N. Corp
Affiliation:
University of Aberdeen, Culterty Field Station, Newburgh, Ellon, Aberdeenshire AB41 6AA, Scotland, U.K. Present address: Scottish Primate Research Group, School of Psychology, University of St Andrews, Fife KY16 9JU, Scotland, U.K.
A. Spalton
Affiliation:
University of Aberdeen, Culterty Field Station, Newburgh, Ellon, Aberdeenshire AB41 6AA, Scotland, U.K. Present address: P.O. Box 246, Muscat 113, Sultanate of Oman.
M. L. Gorman
Affiliation:
University of Aberdeen, Culterty Field Station, Newburgh, Ellon, Aberdeenshire AB41 6AA, Scotland, U.K.
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Abstract

In this study we investigated the effect of rainfall on the home range (calculated over 90 days) of adult female Arabian oryx (Oryx leucoryx) in a reintroduced population in central Oman. We looked at response to rainfall for six rain events in the period June 1986 to January 1992; rainfall was localized on five occasions and on one occasion covered the study area. Response, in terms of range and core area, showed considerable variation between rainfall events, perhaps as a result of variation in ranging behaviour between individual oryx. However, in the first 90 days after localized rainfall the home range and core area of oryx outside rain areas increased before decreasing significantly 91–180 days after rain. In comparison, range and core area of oryx inside areas of localized rainfall either did not change or decreased after rainfall as animals took advantage of improved conditions locally rather than investigating grazing elsewhere. When rain fell over the whole study area, range size did not change, but there was an immediate increase in core area and a reduction in range overlap indicating movement to new areas. During extended drought very localized rainfall caused oryx to move quickly to areas of new rain and by 28 days 70% of all adult females had found fresh grazing. Thereafter numbers declined to around 30% by 225 days, before oryx again moved back into the new rain areas. We attributed this pattern of movement to changes in the nutritional quality, measured as crude protein, of available forage. Data for single animals revealed considerable individual variation in response to rainfall; some animals moved quickly to rain whilst others failed to reach it. This variation had consequences for reproductive success and survival and illustrated that, for the oryx, response to rainfall is a key to desert success.

Type
Research Article
Copyright
© 1998 The Zoological Society of London

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