It seems they do aim for the head region. In captivity things may be different? This coral jumps at the lid for food like a king wanting a mouse, and it often latches on midbody or the first place it encounters the food (I usually feed defrosted snakes). But it may be safe to reason that in their world, they are seeking the head to see if what they are biting is venomous or not, or a species they are capable to kill and eat? My eastern is the same and has taken to water snakes also but is a bit shy when compared to the central american.

Dan