An effort to help the endangered Hawaiian petrel, or 'U'au, recover in number will require the removal of feral animals in the Nu'u parcel of Haleakala National Park/Jim Denny via NPS

A mix of lethal and non-lethal approaches to remove feral animals from more than 2,000 acres in Haleakalā National Park in Hawaii has been approved by the National Park Service.

The land in question, the 2,115-acre Nu’u parcel on Maui, was acquired by the park in 2008. It is one of Maui's largest undeveloped tracts on the leeward slope of Haleakalā. The removal of feral goats, pigs, dogs and axis deer is necessary as part of the habitat restoration plan for the endangered Hawaiian petrel. According to an environmental assessment conducted on the proposal, the petrel, or the ‘Ua‘u, is endemic to Hawaii, and "was once abundant and widely distributed throughout the archipelago."

"Today, the largest known breeding colony is found at Haleakalā Crater on Maui, with other known colonies on Mauna Loa and Mauna Kea, Hawai‘i Island; on Kaua‘i; and on the summit of Lāna‘i. Current threats to ‘ua‘u include habitat loss, predation, groundings, and collision with man-made objects. The Nu‘u area of the leeward slope of Haleakalā, including the HNP Nu‘u parcel, contains habitat suitable for breeding and nesting of endangered ‘ua‘u."

Within Nu‘u, land degradation and loss of habitat caused by the presence of feral goats (Capra hircus), feral pigs (Sus scrofa), and axis deer (Axis axis) are primary concerns. Ungulates trample landscapes and consume vegetation. Additionally, feral dogs (Canis lupis familiaris), which may be attracted to feral ungulates as prey, are also known to be present in the area. Feral dogs prey on ‘ua‘u adults and nests, and are a safety hazard for people entering the area.

Feral goats, pigs, dogs, and axis deer are to be removed from the Nu'u parcel/NPS

Park officials say the first year of action will be the most intensive, with a goal of removing all feral animals from the parcel. They do not have a hard count of feral animals in the Nu'u parcel, as "population numbers are constantly in flux because of control efforts on adjacent lands that cause animals to move and numbers to decrease, and from animal movement based on food availability."

Part of the non-lethal approach involves the construction of a fence around the track, and park staff believe the "majority of the animals are expected to be excluded outside the fence during construction." Lethal methods will include ground and aerial teams removing the animals by killing them with firearms.

Animals occur in treacherous terrain. To ensure the safety of Park staff and helicopter pilots, carcasses will not be retrieved and will be left on-site to decompose. Lethal control of feral animals will be distributed over space and time and a large proportion of the animals are expected to flee out of the area during fence construction. Control efforts disperse herds, leaving small numbers as targets for control. Therefore, high concentrations of decomposing carcasses will not be present in any one area. Following initial efforts, Park staff will monitor the fenced area and implement additional lethal animal control as needed.

The Nu'u parcel was acquired by the park in 2008/NPS