Ecological impacts of feral pigs in the Hawaiian Islands

The foraging habits of exotic ungulate species can directly and indirectly affect native plant and animal distribution and abundance patterns. Most of the studies on feral pig interactions with other biota in the Hawaiian Islands have been published as difficult to access reports to governmental and nongovernmental organizations, graduate student theses, and a few in peer reviewed journals. In this paper we discuss the origins of pig introductions to Hawaii, their feralization process, population expansion, and interactions with native and non-native biota. We also consider the environmental effects triggered by pigs on local ecosystems and biotic communities. Feral pig activities can reduce the abundance of native plant species, enhance conditions for the establishment of invasive non-indigenous plants, and perhaps indirectly negatively impact native forest bird species. Pig foraging and traveling patterns may also lead to physical alteration of ecosystems by increasing soil erosion that may lead to watershed degradation. However, much remains to be learned about the strength and significance of aforementioned interactions and their long-term effects on Hawaiian biota and ecosystems due to some confounding events. Elucidating the dynamics and long-term ecological effects generated by pigs is a crucial step towards increasing our understanding of and more effectively managing biotic interactions.