Everyone learns about carnivores, herbivores, and omnivores at an early age; later one hears about insectivores and piscivores. I think it was when I was playing SimLife or some similar game that I first encountered "frugivore" and "granivore." And it was not until this week while reading about some small creature that I first saw the word "detritivore."
It's not a word that will be useful in everyday conversation. I think I'll save it up to use sometime when I need a good insult.