On the settled islands some Polynesian groups became distinct from one another. A significant example being the Maori of New Zealand. Other island systems kept in contact with each other, such as Hawaii and the Society Islands. Ecologically, Polynesians had the challenge of sustaining themselves within limited environments. Some settlements caused mass extinctions of some native plant and animal species over time by hunting species such as the Moa and introducing the Polynesian Rat. Easter Island settlers engaged in complete ecological destruction of their habtiat and their population crashed afterwards possibly due to the construction of the Easter Island Statues. Other colonizing groups adapted to accommodate to the ecology of specific islands such as the Moriori of the Chatham Islands.