Native Islanders are ritualistic Poptropicans who formerly lived on Shark Tooth Island. They built the temple there and found a cure to the Great Booga Shark's rage. The only apparent islander left is the Medicine Man, who will only talk to other Native Islanders.
Clever with medicine and potions, the natives knew how to take care of the Booga through the years of tradition.
They have their own language, which is somewhat revealed in their temple.
They created some cave art on the walls of the temple.
They all wear grass skirts, as the pictures on the wall in the temple show them, as well as the Medicine Man thinking you're a native islander because of your grass skirt.
Building the temple, the Native Islanders apparently began to worship the Great Booga Shark. Concocting the Calming Potion with the materials on the island, they kept the Booga Shark asleep until something happened, making them disappear. Only one islander is left, the Medicine Man.
With the natives not there to put the shark to sleep, he wakes up and starts prowling the waters of the island.