Red deer
The islands around Lake Manapouri are of varying size and isolation. Many of the islands contain virtually unmodified vegetation. However, there is large diversity between islands in habitat biodiversity, with some islands being completely devoid of plants and soil and other rich in both. There is confusion as to some differences with some researchers finding that the area of an island plays a role in species richness with others find no correlation at all. Red deer have greatly modified much of Fiordlands' vegetation however only the two largest islands within Lake Manapouri contain introduced red deer while other islands are only occasionally visited by deer. The smaller islands around Lake Manapouri are extremely unusual as they contain natural vegetation which has not been harmed by red deer, as the red deer have not been able to reach the islands. On these islands palatable plants as well as deep moss mat on the forest floor persist under the dense understory layers of the forest.