Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Category: baby animals 
Words: buck, bambi, lust, fawn, deer
lust

Category: chocolate food 
Words: fudge, chocolate cake, pudding, unwarranted, heavy
unwarranted

Category: animals 
Words: ostrich, geese, mallet, duck, crouch

crouch