This is because foxes are not native to Hawaii. The closest Hawaiian word, ʻiole (pronounced ee-oh-leh), refers to rats.
You could try to explain what a fox is, using descriptive words like:
* ʻīlio hihiu (ee-lee-oh hee-hee-oo) - meaning "wild dog"
* ʻīlio liʻiliʻi (ee-lee-oh lee-ee-lee-ee) - meaning "small dog"
* ʻīlio me ka hulu ʻulaʻula (ee-lee-oh meh kah hoo-loo oo-lah-oo-lah) - meaning "dog with red fur"
It's important to note that these are not exact translations of "fox," but rather descriptions that might help someone understand what you are talking about.