The most likely reason for the sudden encounter between these two Zebra's is the rising levels of testosterone amongst stallions.
Before the mating season arrives all the Stallion's are normally seen establishing their pecking order and the stronger one's automatically get to mate.
Model Canon EOS-1D Mark IV
Lens EF300mm f/2.8L IS USM +1.4x
Focal Length 420mm
Shutter Speed 1/640
Taken At Sun, Oct 21, 2012 6:48 PM