ANIMAL TREASURE ISLAND

Jim and his mouse friend Gran toll away working as innkeepers. They dream of sailing far away on their own boat. One day, a mysterious fellow appears at the inn and gives them a map. It's the map to Treasure Island. So they decide to make their own boat, and sail away treasure hunting. But it’s not as easy as they think when the run into a group of unsavory pirates led by the dastardly Captain Silver. Silver wants the treasure for himself, and it is up to Jim, Gran, and their new friend Kathy, to beat him to it. (Source: Discotek) — Description from AniList community (anilist.co).