It seems like you're trying to make a joke or a silly scenario! 😄 Would you like to try making up a story about a hippo and a dog who do live on an island together?
Where is all the hippo food in dog island?
There's no such thing as "Dog Island" or "Hippo Island". Hippos live in Africa, mainly in rivers and lakes, while dogs are domesticated animals found all over the world. They don't live on islands.