Zebra Foal drawing progress

Its been a while since i took on a largish piece and i'd forgotten just how time consuming the background toning can be.This one has had multiple layers of H,HB and B grade pencil and may well need more layering but ive got bored with that for now and moved onto the zebra itself.The zebra is backlit and therefore has areas of strong contrast between shadow and strongly lit areas which is proving quite tricky to pick out hairs catching the light.ive layered up the front of the zebra's mane with every grade of pencil from H thru to 3B and left the tip of the mane hairs lighter where the sun behind has lit them up,these i shall work up later,once ive worked out the best way to depict them effectively.Ive also started the base layering on the animals ears with a layer of H grade pencil.