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Open Access Publications from the University of California

Eradication Efforts for Hybrid-Mouflon Sheep in Palila Critical Habitat on Mauna Kea


Palila were listed as a federal endangered species in 1967, primarily due to two centuries of habitat destruction by non-native ungulates. The United States Fish and Wildlife Service designated Critical Habitat for palila in 1977, and federal court rul-ings in 1979, 1987, and 1998 mandated Hawai‘i Department of Land and Natural Resources (DLNR) to remove all sheep and goats from Critical Habitat. In 2010, over 30 years since the original ruling, DLNR initiated construction of a 6-foot-tall ungulate- proof fence around Mauna Kea to eliminate ingress of feral sheep, hybrid-mouflon sheep, goats, and cattle. Twenty-four miles of fence were completed around the southern portion of Mauna Kea by 2013. DLNR also developed a strategic plan for the permanent removal of non-native ungulates from palila critical habitat (PCH) and received a Competi-tive State Wildlife Grant to fund eradication efforts. Implementation of the plan and dispersal of the funds began in April 2013. A population estimate was conducted in May 2013 using distance sampling that produced a point estimate of 2,046 hybrid-mouflon sheep with a 95% confidence interval of 482- 3,614 sheep. From January 1 2003 to February 6 2014, 3,270 sheep and 26 goats were removed from PCH by aerial shooting (2,150), aerial drives (228), and public hunting (792). Of the 2,147 sheep shot during aerial shooting, 2,081 were shot when not tracking Judas sheep (sheep fitted with radio collars that facilitate locating herds from the helicopter), and 66 were shot when tracking Judas sheep. With the population reduction, aerial shoot efforts are now dependent upon tracking the 17 Judas sheep currently equipped with radio-collars to find herds that have learned to avoid aerial hunting by hiding under the forest canopy. Future aerial shoots will be conducted on a monthly basis and missions will likely to be 2 days. To reach the goal of sheep eradication in PCH prior to the depletion of remaining funds, it is essential to track all Judas sheep every mission to increase removal rates. Otherwise, the sheep popula-tion will likely recover and continue to damage the remaining forest in PCH that palila depend upon.

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