The plains variety of this animal has gray markings that are known as shadow stripes
This kind of Zebra generally has broad stripes, with lighter 
shadow stripes in... [DOC] [TLE] The Adaptive Significance of Coloration in Mammals - BioScience [PAR] The most salient point about the evolution of animal coloration is that different ... 
pale species in desert and open environments, red and gray species in rocky ... 
itself cannot be taken as evidence that selection has acted to reduce shadow.