What's a word that suggests having very long ears?
Solution 1:
I believe you're looking for macrotous.
Solution 2:
You should probably just go with "long-eared" — I don't think there are any specific terms meaning that, except possibly scientific ones with Latin roots.
Solution 3:
Huh, you might say the animals have pendulous ears. That emphasizes the weight of the ears, as well as suggesting they hang in a droopy fashion.