Complex sentence: Geckos' toes operate well below their full attractive capabilities most of the time, because the margin for error is great depending upon the surface roughness, and therefore the number of setae in contact with that surface.
Split into simpler sentences: Geckos' toes operate well below their full attractive capabilities most of the time. This is because there is a great margin for error depending upon the roughness of the surface, and therefore the number of setae in contact with that surface.