The first introduction was the small pig the Polynesians brought with them. It is not thought to have ranged to more than 3,000 feet and is not thought to have caused great damage. However, when the larger domestic pig ran wild after its introduction by Europeans, the two hybridized, and the resulting larger feral pig ranges higher and does much more damage. Below, a tree fern has been destroyed by pigs, which eat the starchy core. The resulting shell fills with water and becomes a breeding place for mosquitoes.
Mosquitoes can carry avian malaria, a disease threatening the native honeycreepers.