Hi Luke, How interesting. I have seen something very similar.
Many would think the gouldi group to be amoung the most intelligent of monitors, but they seem to hunt straitlined. That is, they go strait after their prey. They have a hard time figuring the barrier problem.
But, Many would think Albigs are amoung the dumbest of monitors, yet I have at least one that figure out how to go around a barrier thing. And She did it quickly. She was chasing an adult mouse, in a very ackward matter, going full bore after the mouse, the mouse shot between the outside wall of the cage and a large water tub and hiding area. The monitor imediately went around the obstacle and caught the mouse coming out the other side. The obstacle was two feet by three feet. She has done this several times. Hmmmmmmmmmm. An Argus would still be trying to get between the wall and the tub, digging like crazy.
I think it has to do with inherent behavior, The gouldi complex, are probably very success at simply running down prey and digging it up. Albigs being very slow, in comparision, must outsmart their prey. Hmmmmmmmm
Maybe the smartest monitor species is the species with the least specific requirements and the largest range. FR