In a poem "Where knock is open wide" Roethke wrote
A kitten can
Bite with his feet.
Roethke told his students that a function of poetry was to "give a cat its right name." And perhaps that is why he discarded this line from a draft---
A piece of a mouse/ The cat wouldn't eat.
We learn these details from his biography, The glass house: The life of Theodore Roethke, by Allen Seager (1968). Roethke won a Pulitzer for his poetry in 1954.