hedgehog vs gnawer

hedgehog and gnawer both are nouns.

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

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

hedgehog: relatively large rodents with sharp erectile bristles mingled with the fur
gnawer: relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing

Other hypernyms of hedgehog include rodent.

hedgehog (noun)	gnawer (noun)
small nocturnal Old World mammal covered with both hair and protective spines	relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing
relatively large rodents with sharp erectile bristles mingled with the fur