I noticed the same aesthetics problem a while back but thought that it might have been related to reduced quality settings. I recently was around them again on my home PC (with Ultra quality) and found the same problem. Molesaurs now seem to be dark grey-ish in color from afar (first panel below), but once they get to about 5 meters of you (second panel) they turn into a black silhouette. In addition, if they are behind a hill (third & fourth panels) you can see the silhouette clearly through the ground. The third through fourth panels below are all pics of the same mole as it was running towards me.