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

he unique native flora of the T Hawaiian Islands, which evolved in the absence of ungulates (grazing animals), is highly vulnerable to damage by trampling and browsing. Wild ungulates introduced into Hawaiì 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. Geologi- cal Survey scientists are studying Mouflon (wild Mediterranean sheep), like these in the Kahuku Unit of Hawaiì Volcanoes National Park, these wild ungulates in order threaten the fragile native flora of Hawaiì by browsing, bark-stripping, and trampling. The Hawaiian Islands to develop more effective con- originally had no ungulates (grazing animals), but mouflon and several other species were deliberately trol measures that help protect 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 Hawaiì`s endemic flora. Robert Stephens.

For millions of years, the Hawaiian Islands unique, and land animals were mostly limited to Introduced Wild Sheep and Deer in Hawaiì lay undiscovered by humans in the middle of the invertebrates and birds. Before humans came, Pacific Ocean. The fauna and flora that found the only mammals, apart from seals that hauled European mouflon (Ovis gmelini their way to the islands and evolved there were up on the beaches, were insect-eating bats. When musimon), closely related to the ancestors of Polynesians settled Hawaiì more than a thousand domestic sheep (O. aries), are wild sheep that years ago, they brought with them domesticated originated from Asia Minor. Mouflon were dogs, pigs, and fowl (chickens). Rats arrived as subsequently introduced to many areas of the stowaways. Inevitably, some of these animals world, including Hawaiì. On islands lacking escaped into the wild and established feral native ungulates, populations of introduced populations, which began to have an impact on mouflon have grown rapidly and severely dam- the native flora. After theislands were found aged native flora. by Western explorers, the influx of non-native Introduced into the Hawaiian Islands begin- species into Hawaiì increased. Since the middle ning in the 1950s, mouflon currently occur wild of the 19th century, this has included deliber- on Länaì and the Island of Hawaiì. On Hawaiì, ate introduction of several large wild ungulates mouflon and feral sheep were crossbred and (grazing animals). The native flora, which released on the large shield volcano Mauna Kea developed in the absence of large land mammals, beginning in 1962. A large hybrid population now is extremely vulnerable to browsing, trampling, surrounds Mauna Kea and extends to the northern and bark stripping by ungulates, and the effects of part of the volcano Mauna Loa. In 1968 a popula- these introduced species has been severe. Some tion of wild-type mouflonwas introduced to the domesticated ungulates have been in Hawaiì Kahuku Ranch (now a unit of Hawaiì Volcanoes for hundreds of years, but wild species that National Park) on Mauna Loa for trophy hunting. have never been domesticated are now rapidly These animals now range over the southern part increasing in range and numbers. Wild ungulates of Mauna Loa in the Kahuku area and adjacent behave differently and are much more elusive public and private lands. Both herds have dramat- and difficult to manage than livestock species that ically expanded their range into forest reserves, Browsing by wild ungulates threatens native were once domesticated and have become feral. where they are destroying endangered native Hawaiian plants. This mämane tree sapling in Palila Thus, Hawaiì’s plants are facing a relatively plants such as silverswords (Argyroxiphium spp.). Critical Habitat on Mauna Kea, Island of Hawaií, new threat. Controlling these wild ungulates has Axis deer (Axis axis), otherwise known as has been stripped of most of its foliage. become a major conservation concern. chital, originate from India, Sri Lanka, and Nepal.

U.S. Department of the Interior USGS Fact Sheet 2008–3102 U.S. Geological Survey 2008 161°W 159° 157° 155°

23° N Kauaì black-tailed deer 1961 mouflon 1962* Oàhu axis deer after 1898* Molokaì axis deer 1868 Maui axis deer 1959 21°

Mauna Kea mouflon and Lana`i mouflon-feral axis deer 1920 sheep hybrids mouflon 1954 1962 pronghorn 1959*

Island of Hawai`i

19° Mauna Loa 0 50 100 MILES mouflon 1968 0 100 100 KILOMETERS

Starting in the middle of the 19th century, several species of wild ungulates have been introduced into the Hawaiian Islands, eventually inhabiting almost all the main islands. This map shows the species and their dates of introduction on each island. Asterisks (*) indicate populations that later died out.

They have been introduced to many parts of the in numbers, threatening native forests in natural consequence of their evolutionary history with United States (including California, Texas, and areas. The Oàhu population was reduced to a large predators, many ungulates have very high Hawaiì) and to Australia. Axis deer were brought remnant herd in Moanalua Valley by 1962 and reproductive rates, causing rapid population to the Hawaiian Islands from India in late 1867 eventually died out. Although introducing axis growth in Hawai’i, where there are no predators. as a gift to King Kamehameha V and released deer to the Island of Hawaiì was debated for The Columbian black-tailed deer on Molokaí in 1868. Some were moved to many years, it was never undertaken. (Odocoileus hemionus columbianus) is a Oàhu before 1898 and some to Länaì in 1920. Axis deer in the Hawaiian Islands damage subspecies of mule deer from the northwestern Axis deer were also released on Maui in 1959. agricultural crops and native and ornamental United States. In 1961, 35 animals were intro- Although axis deer have been wild on Länaì and vegetation through browse and bark stripping, duced from Oregon to Puù ka Pele Game Man- Molokaì for many decades, the more recently cause erosion, are frequently hit by vehicles, and agement Area on Kauaì. This herd has grown to introduced Maui population has rapidly increased may carry diseases that can infect humans. As a a population of more than 700 on both sides of Waimea Canyon, including Kökeè State Park. American pronghorn antelope (Antilo- Axis deer (fawn) Columbian black-tailed deer capra americana) were brought to Länaì in 1959 from Montana. After an initial population increase to 250 animals in 1966, pronghorn declined to fewer than 12 by 1983 and appar- ently now no longer exist on Länaì. Pronghorn represent one of the few introductions of a wild ungulate to Hawaiì that failed entirely.

Impact on Hawaiian Flora and Fauna Since 1778, nine percent of the native Hawaiian flora has gone extinct, in good part as a result of the introduction of non-native species. In addition, where non-native herbivores (plant-eating animals) have been introduced, in Hawaiì and elsewhere worldwide, there is usu- Two species of wild deer have been introduced into Hawaiì, axis deer and Columbian black-tailed deer. ally also an increase in the relative abundance of In their native range, many axis deer fawns fall victim to predators; with no predators in Hawaiì, the invasive plants from their native range, which deer’s numbers can increase rapidly. Photographs courtesy of Charles van Riper III. then often outcompete local species. The wild ungulates discussed here have caused tremen- 156°N 155°N dous damage to Hawaiì’s native flora. On Mauna Kea, the habitat degradation in the mämane-naio forest, which the endangered Hawaiian finch, Palila (Loxioides bailleui) rely on, resulted in two court orders to eradicate both pure and hybrid mouflon, along with feral domestic sheep and goats. Nearly two decades of intensive population control were required 20° 20° for habitat conditions to improve on Mauna N Kea. The Mauna Kea silversword (Argyro- xiphium sandwicense), an endangered plant, Wild introduced mou- still suffer browse damage when even small flon and mouflon-feral numbers of hybrid mouflon are present. sheep hybrids are dam- Where mouflon have occasionally aging native flora and invaded fenced areas in the Mauna Loa strip fauna in several areas of Hawaiì Volcanoes National Park, they have on the Island of Hawaiì, destroyed outplanted Ka`ü silverswords (A. including Palila Critical kauense)—another endangered plant, dam- Habitat on Mauna Kea and the Kahuku Unit aged the threatened Hawaiian catchfly (Silene of Hawaiì Volcanoes hawaiiensis), and stripped bark from important National Park on Mauna forest trees, such as koa (Acacia koa) and Loa. mämane (Sophora chrysophylla). A large and growing population of mouflon continues to threaten and degrade endangered plants such as the Ka`ü silversword and the habitats of endangered forest birds throughout Mauna Loa. Axis and Columbian black-tailed deer 19° 0 50 MILES 19° cause similar environmental damage. They consume progressively less palatable plants 0 100 KILOMETERS until no edible vegetation is available. Under extreme drought conditions, axis deer will eat 156° 155° bark from trees. In addition to stripping bark, bucks also rub their antlers on tree trunks island of Hawaiì, a founding population of 11 In the native range of Columbian black- and branches. This can effectively girdle the individuals has increased to more than 2,500 in tailed deer, mountain lions and other predators tree and result in the death of mature trees. 36 years, even while under substantial hunting account for as much as 40% of fawn mortality. Deer have their highest concentrations in the pressure for trophies. Mouflon are polyga- In Hawaiì the deer suffer no predation other fragile, seasonally wet areas below the cloud mous, and their populations can grow rapidly than human hunting. forests. Here, they create trails and pathways when the ratio of females to males is high. An Unlike feral sheep, goats, and pigs, which through thick vegetation and cause erosion abundance of high-quality food can also lead to were domesticated before their arrival in through hoof action. In wet forest areas, the a lower age of first pregnancy and higher lamb Hawaiì, mouflon and deer were never domes- trails increase runoff through soil compaction survival, further increasing population growth. ticated. These wild ungulates present new and by decreasing the mossy layer available to Axis deer have high reproductive rates, challenges to control efforts in Hawaiì. They retain water. These trails also damage cultural which compensate for predation by leopards, are able to jump over most fences designed for and archaeological resources. The interac- tigers, and Indian wild dogs in their native feral animals, and when being pursued, they tion of browsing and soil compaction by feral range. In the absence of predators, as in disperse into small groups and hide in dense pigs, goats, and axis deer on east Molokaì Hawaiì, introduced populations exhibit annual cover. Social behaviors also differ. Mouflon has reduced the `öhià-hapuù rainforest to population growth rates of 20–30%. On Länaì segregate by sexes and only form large groups a grassy scrubland, and runoff of silt from and Molokaì, some females reach sexual when breeding, thus limiting efficient hunting this degraded habitat threatens the coral reef maturity by 4–6 months of age, and most do periods. Because they disperse widely over the ecosystem on the southern coast. so by the end of their first year. In years when landscape alone or in small groups, common Without fences, deer will increase and forage conditions are good. more than 90% of control techniques that rely on radiotelemetry invade new areas, particularly on Maui and mature females produce fawns. are largely ineffective for mouflon. Kauaì. Axis deer have been observed to jump Axis deer graze and drink water in open The hybrid mouflon-feral sheep of fences 8 feet (2.6 m) tall. Building fences high areas during the twilight of morning and Mauna Kea are larger than wild-type mouflon enough to totally exclude deer is expensive evening and rest in cover during the warm- and have a wider variety of coat colors. and difficult. Therefore, supplementary control est part of the day. They are usually found in Managers are concerned that under intense efforts are often needed within areas enclosed small family groups of 15–24, and harems are hunting pressure or control efforts, the varia- by lower fences. Axis deer are also damaging uncommon. However, herds of nearly 100 ani- tion in coat coloration may lead to selection existing fences throughout the western slopes mals are reported on Länaì and Molokaì, and for cryptic colors that blend with the environ- of Haleakalä on Maui presenting a major con- a herd as large as 300 was recently reported ment. These superior physical traits of size cern to natural resource managers. on Maui ranch pasturelands. Although axis and color variation are examples of hybrid Biology and Spread of Wild Ungulates deer are rarely found above 1,160 m (3,800 ft) vigor. Although feral sheep and goats have elevation in their native range in Nepal, they been effectively eliminated from Mauna Kea, In the five decades since their first have been observed above 2,150 m (7,050 ft) hybrid mouflon continue to expand their introduction to the Hawaiian Islands, mouflon on Maui. They are present from sea level to range and have invaded other natural areas, have become locally abundant, as they have the highest point on Länaì (1,030 m; 3,380 including Hawaiì Volcanoes National Park, on other island groups. In the Kahuku Unit ft), and they exist throughout all but the most despite the presence of fences designed for of Hawaiì Volcanoes National Park on the remote areas of Molokaì. feral animals. develop and implement monitoring protocols that will allow managers to understand the effectiveness of different strategies. The work of scientists in studying the A flowering wild ungulates of Hawaiì is part of the U.S. Mauna Kea Geological Survey’s efforts to understand and silversword help preserve threatened ecosystems. If effec- (foreground) has tive control measures for these wild ungulates been trampled are not implemented, it may be difficult if not and browsed by impossible to prevent them from expanding wild mouflon or mouflon-feral their ranges and numbers in Hawaiì. This in sheep hybrids. turn would make it far more difficult to protect Behind it stands Hawaiì’s vulnerable endemic flora. a surviving silversword. The active Further Reading volcano Mauna Loa dominates Anderson, S. B., 1999, Axis deer overview the horizon. and profile: [www.hear.org/hnis/ reports/HNIS-AxiAxiV01.pdf]. Hess, S., B. Kawakami, B., Okita, D., and Medeiros, K., 2005, A preliminary assessment of mouflon abundance at the Kahuku Unit of Hawaiì Volcanoes National Park: U.S. Geological Survey Open File Report OF 2006-1193 Control and Management of Wild Hawaiì. These ungulates do not stay on public [http://pubs.usgs.gov/of/2006/1193/]. Ungulates land, and in many areas, limited land access Maui axis deer group, 2002, Initial findings precludes hunting. Previous efforts at eradica- for a Maui deer management plan: The conservation of rare and endangered tion have not generally been successful, because [www.nps.gov/applications/parks/hale/ species in Hawaiì often includes the con- of the evasive behavior of the animals. More ppdocuments/ACF214.doc]. struction of enclosures that protect only a few effective hunting programs and control tech- Robichaux R., Bergfeld, S., Bruegmann, individuals within a small area. If rare plants niques are needed for wild ungulates in Hawaiì. M., Canfield, J., Moriyasu, P., Ruben- are relegated to such small areas, there is little Unsupervised public hunting has generally been stein, T., Tunison, T., and Warshauer, hope of guarding their long-term survival— ineffective for controlling ungulates in Hawaiì. F., 2000, Reintroducing Hawaiì’s plants cannot effectively disperse and adapt to Although a closely directed hunting program has silverswords: Endangered Species environmental changes under these conditions. reduced mouflon abundance in the Kahuku area, Bulletin, v. 25, p. 22-23. If, however, wild herbivores are controlled over it has also resulted in increased reproduction, Sakai, A. K., Wagner, W. L., and Mehrhoff, large areas, natural population processes and which could slow future control efforts. This is L. A., 2002, Patterns of endangerment local adaptation can occur, as well as recovery because trophy hunting, which focuses on males in the Hawaiian flora: Systematic for entire native plant communities. To ensure with impressive horns, can shift the sex ratio of Biology, v. 51, p. 276-302. long-term survival of native plants, effective populations and contribute to higher population Waring, G., 1996, Preliminary study fence designs and management strategies are growth. If control efforts are directed at females, of the behavior and ecology of needed to exclude wild ungulates from pro- however, growth rates could be reduced. axis deer (Axis axis) on Maui, tected natural areas in Hawaiì. Population monitoring is critical for Hawaiì: Research report to Hale- Managing wild ungulates for sustained- understanding management actions, growth rate akala National Park and the National yield public hunting is problematic, because they trends, and range expansion. It is also important Park Service [www.hear.org/ are extremely difficult to census, hunt, contain, to develop effective strategies to reduce the AlienSpeciesInHawaiì/waringreports/ and control in the remote and rugged terrain of expense and effort of control programs and to axisdeer.htm].

Mouflon in Kahuku area, Island of Hawaiì 5,000 Steven C. Hess Edited by Annual growth rate (%) Peter H. Stauffer 4,000 22.0 21.1 Graphic design by 20.0 Stephen L. Scott 3,000 COOPERATING ORGANIZATIONS Hakalau Forest National Wildlife Refuge Hawaiì Volcanoes National Park 2,000 For more information contact: NUMBER OF ANIMALS

800 animals removed Steven C. Hess 1,000 (808) 967-7396 x286 U.S. Geological Survey Pacific Island Ecosystems Research Center 0 Kilauea Field Station

P.O. Box 44

2001

1971

1983

1998

1992 2004 1995 1977

1968

1986

1989

1980 1974 Hawaii National Park, HI 96718 The mouflon population in the Kahuku area of Mauna Loa doubled every 3-4 Email: [email protected] years from its initial introduction of 8 animals in 1968 to an estimated 2,586 http://biology.usgs.gov/pierc/ in 2004. An assumed annual rate of increase of 21.1 percent (the bold black line) best accounts for the known abundance at those two points in time This Fact Sheet and any updates to it are available online at: http://pubs.usgs.gov/fs/2008/3102 (stars) and the removal of about 800 individuals in 1994.