muskrat vs gnawer

muskrat and gnawer both are nouns.

Word	Noun	Adjective	Verb	Adverb
muskrat	Yes	No	No	No
gnawer	Yes	No	No	No

As nouns, gnawer is a hypernym of muskrat; that is, gnawer is a word with a broader meaning than muskrat:

muskrat: beaver-like aquatic rodent of North America with dark glossy brown fur
gnawer: relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing

Other hypernyms of muskrat include rodent.

muskrat (noun)	gnawer (noun)
beaver-like aquatic rodent of North America with dark glossy brown fur	relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing
the brown fur of a muskrat