Pacific Island Ecosystems Research Center

U.S. Geological Survey
Fact Steet 2008-3102
Version 1.0

Wild Sheep and Deer in Hawai‘i—a Threat to Fragile Ecosystems

By Steven C. Hess


Photo of sheep crossing rugged rock outcrop of 'a'a
Mouflon (wild Mediterranean sheep), like these in the Kahuku Unit of Hawai‘i Volcanoes National Park, threaten the fragile native flora of Hawai‘i by browsing, bark-stripping, and trampling. The Hawaiian Islands originally had no ungulates (grazing animals), but mouflon and several other species were deliberately introduced, mainly for recreational hunting. Traditional control methods—including hunting—have proved largely ineffective in limiting the increase and spread of these introduced wild ungulates. Photo courtesy of Robert Stephens.

The unique native flora of the Hawaiian Islands, which evolved in the absence of ungulates (grazing animals), is highly vulnerable to damage by trampling and browsing. Wild ungulates introduced into Hawai‘i in the past 150 years, including mouflon, axis deer, and mule deer, have severely harmed the native flora. Control measures used against feral animals do not work as well against these wild animals. Trophy hunting tends to alter sex ratios and increase population growth. U.S. Geological Survey scientists are studying these wild ungulates in order to develop more effective control measures that help protect Hawai‘i’s endemic flora.

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For questions about the content of this report, contact Steven Hess

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