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Conspicuousness
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The Arabian oryx is very white and
with the sun behind an observer a single animal in the
open is clearly visible to the unaided human eye up to 3
km distant. Oryx take advantage of their conspicuousness
when searching for a herd by standing motionless on
prominent ridges to advertise themselves. |
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Yet against the sun, the oryx can be invisible at 100 m
because of glare and lack of reflection from the animal.
Similarly when an oryx moves into shade, particularly if
dappled, it is also very hard to see. This is because of a
combination of effects: a ubiquitous 'white' light due to
atmospheric dust and heat shimmer reduces visibility and
definition, and the oryx often lie in shallow scrapes under
trees with their horn tips lost against the canopy. Arabian
oryx calves are a sandy-brown colour for the first 2-3
months of their lives, in common with the other species.
This camouflage is an obvious adaptation to reducing
predation risk during their lying-out phase.
 Despite
very acute eyesight allowing them to detect potential
predators from afar in the open, shading oryx are most
reluctant to leave shade, even in a hunted population when
the source of danger must have been seen for some time. This
reluctance to move is probably a response to the potentially
fatal problems of thermo-regulation if an oryx has to run
when it should be in the shade. This advantage of the white
coat is thought to outweigh any disadvantage of being highly
visible to predators at some times.
Locomotion and
endurance
>>
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