"There is a tortoise behind the duck," I think you mean. "Drake" may be technically correct, but no one uses that word.
Can it also mean temporally after? Like a vet saying "There is a turtle after (I treat) the duck"
Well, מֵאֲחוֹרֵי functions as a preposition and must be followed by a noun ("behind a desk", behind my back"), but מֵאָחוֹר functions as an adverbial phrase of location ("I shot him in the back, I left him behind, he shot him from behind") and is not followed by a noun.