Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
seabirds, and Hawaiian forest birds (Tomich 1986, Snetsinger et al. 1994, Mostello 1996, Smucker et
al. 2000, Brisbin et al. 2002, Engilis et al. 2002, Mitchell et al. 2005, USFWS 2005a, USFWS
2005b). At the HFU, rats were found to be the dominant food item for cats, occurring in 75 percent
of sampled scats (Smucker et al. 2000). Cats are one of the main predators feeding on nēnē eggs and
goslings at the HFU.
Cats have a universally damaging effect on insular forest birds and nesting seabirds (Moors and
Atkinson 1984, Statterfield et al. 1998, USFWS 2005a). Species with low reproductive rates and high
parental investment are particularly susceptible. In addition, cats are known to carry the protozoan
that causes toxoplasmosis. This disease is caused by the protozoan Toxoplasma gondii that has been
known to kill the endangered „alala and nēnē (TMA 2007). Several captive released „alala in the
early 1990s that died were diagnosed with toxoplasmosis (Ball, pers. comm). It is recommended that
all cats be removed prior to additional „alala releases at the KFU (Winter and Wallace 2006).
At HFU, live-trapping and removal is used for control of cats during the nēnē breeding season
October-April. Traps baited with sardines are deployed around primary nēnē nesting areas. These
traps are equipped with “gosling guards” which are placed in front of the opening to inhibit young
nēnē from entering the traps, and yet allow predators to enter. Traps are checked once a day and
predators that are caught are humanely euthanized using CO2 (Jeffrey, pers. comm.). Three cats were
trapped in 2007 (USFWS 2007a). No cat control method is currently used at the KFU.
Goats (Capra hircus)
Goats were introduced to Hawai„i around 1778 by European explorers. Large herds were present by
the 1850s. Tomich (1986) identifies goats in Hawai„i as the subspecies Capra hircus hircus. Wild
goats are established on Hawai„i, Maui, Kaua„i, Moloka„i, and Kaho„olawe (Scowcroft and Hobdy
1987). The first known major goat control began at Hawai„i Volcanoes National Park in the 1960s
(Spatz and Mueller-Dombois 1973). Goats are not known from the HFU but a few dozen goats are
currently present on KFU (USFWS 2008). Goats prefer open habitat, such as grasslands, and scrub
but will take cover in open forests. They typically move in groups, with males more nomadic than
females. The home ranges of goats vary from 328 ft to 12 mi wide (Atkinson and Atkinson 2005).
Similar to other ungulates in the Hawaiian Islands, goats are considered to be habitat modifiers.
Goats have been implicated in causing declines of native woody legume species, such as the
nutritious māmane (Tomich 1986) and koa. They have been observed consuming the shoots and root
suckers of koa and therefore inhibiting reproduction (Scowcroft and Hobdy 1987). By removing
native species, goats also help facilitate the invasion of noxious plant species, reducing native habitat,
cover, and food resources for native species that depend upon these plants (USFWS 2008).
Sheep (Ovis aries)
Sheep were brought to the Hawaiian Islands by Captain Cook in 1778. Populations became
established on Hawai„i Island and formerly Kaho„olawe (Atkinson and Atkinson 2005). Sheep
populations that had established in Mauna Kea‟s subalpine woodland in 1825 reached about
40,000 animals by the early 1930s. Public hunting in the area decreased the population to about
5,000 sheep in 1955, and by 1970 the sheep population had dropped to 1,500 (Scowcroft and Conrad
1992). Because sheep populations were having an impact on the endangered palila, the State of
Hawai„i was charged with violating the ESA, and all sheep were court ordered to be removed from
4-90 Chapter 4. Refuge Biology and Habitats