I sometimes wonder how having 2 pairs of ears would work. Obviously the fox ears are better at picking up sound than the human ears, which makes those redundant. Except from a practical viewpoint, that wouldn't make sense.
I picture them as the different kinds of passive sonar you'd find on a submarine. High/medium frequency human ears for short range hearing and low frequency animal ears for sounds across long distances. I don't know if it could really work like that, but it's fun to think about.
