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

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Within KFU, the Refuge estimates that currently there are more than 300 wild cattle and an unknown
number of pigs, sheep, mouflon, donkeys, and horses. These ungulates are primarily concentrated in
the mesic belt (Ball, pers. comm.), which receives between 50-75 in of annual rainfall. Physical,
chemical, and biological population control methods are used on invasive mammals and their
removal, while frequently justified biologically, is not without controversy. The elimination of
grazers in altered habitats can also release other species from browsing pressure and result in an
increase in nonnative and invasive plant species (Scowcroft and Conrad 1992, Cabin et al. 2000, Van
Driesche and Van Driesche 2000). At the KFU, the removal of ungulates may be controversial
because eliminating grazers will increase the potential for fire. This could both eliminate native
habitat and impact adjacent landowners. Wildfire Management Plans (2002a, 2002b) have been
developed for both units. Additionally, a strategy in this CCP identifies developing a fire prevention
program for both units.
Cattle (Bos taurus)
Cattle were released on the Island of Hawai„i in 1793 by Captain Vancouver (USFWS 1996b).
Currently, cattle exist on the all of the main Hawaiian Islands except for Kaho„olawe. These feral
animals have a wide distribution, ranging from lowland dry forests to montane grasslands and
subalpine scrub (Tomich 1986, Atkinson and Atkinson 2005).
Cattle ranching was the primary historical land use on the HFU for over 100 years, although other
forms of ranching may have occurred. Reports of cattle at Hakalau first occurred in the early to mid-
1800s. Intensive grazing occurred primarily above 5,400 ft (USFWS 1996b). Cattle grazing has been
eliminated on the HFU; however, cattle remain throughout adjacent properties.
At the KFU, cattle are the most widespread ungulates. Recent estimates suggest roughly 300 wild
cattle inhabit the KFU boundaries at all elevations. Historically, cattle grazing was the primary land
use of the former 60,000 acre McCandless Ranch. The Three Mountain Alliance Management Plan
(2007), a landscape level effort that spans large areas and multiple ownerships of Hawai„i Island,
considers the KFU as a high priority area for feral cattle control.
Due to their large size, cattle can have a large impact on native ecosystems (USFWS 2008). Cattle
have been regarded as the “single most destructive agent to Hawaiian ecosystems, particularly to koa
forests” (Atkinson and Atkinson 2005). These ungulates can degrade native forest by eating or
trampling native vegetation, accelerating erosion, and promoting the invasion of nonnative plants
(USFWS 2008). In particular, cattle suppress regeneration of koa and the growth of māmane forests
(Atkinson and Atkinson 2005). Soil properties are also altered due to the presence of cattle. The
animals can change soil structure and pH, as well as its ability to retain water and nutrients (USFWS
1996b).
The impact of cattle is apparent on both units of Hakalau Forest NWR. Nearly all the trees have been
eliminated on the HFU areas above 6,000 ft as a result of over 100 years of grazing. Certain areas
covered by old a„a lava flows have more forest, suggesting that cattle were less able to transverse this
substrate and degrade the forest (USFWS 1996b). On the other hand, removing cattle on the HFU has
increased the nonnative grass fuel load considerably (USFWS 2002a).
4-86 Chapter 4. Refuge Biology and Habitats