Biology and Impacts of Pacific Island Invasive Species. 9. Capra Hircus, the Feral Goat (Mammalia: Bovidae) Author(S): Mark W

Home , Capra (genus), Feral goat, Goat

Biology and Impacts of Pacific Island Invasive Species. 9. Capra hircus, the Feral Goat (Mammalia: Bovidae) Author(s): Mark W. Chynoweth , Creighton M. Litton , Christopher A. Lepczyk , Steven C. Hess , and Susan Cordell Source: Pacific Science, 67(2):141-156. 2013. Published By: University of Hawai'i Press DOI: http://dx.doi.org/10.2984/67.2.1 URL: http://www.bioone.org/doi/full/10.2984/67.2.1

BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder.

BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Biology and Impacts of Paciﬁc Island Invasive Species. 9. Capra hircus, the Feral Goat (Mammalia: Bovidae)1

Mark W. Chynoweth,2,5 Creighton M. Litton,2 Christopher A. Lepczyk,2 Steven C. Hess,3 and Susan Cordell 4

Abstract: Domestic goats, Capra hircus, were intentionally introduced to numerous oceanic islands beginning in the sixteenth century. The remarkable ability of C. hircus to survive in a variety of conditions has enabled this animal to become feral and impact native ecosystems on islands throughout the world. Direct ecological impacts include consumption and trampling of native plants, leading to plant community modiﬁcation and transformation of ecosystem structure. Al- though the negative impacts of feral goats are well known and effective management strategies have been developed to control this invasive species, large populations persist on many islands. This review summarizes impacts of feral goats on Paciﬁc island ecosystems and management strategies available to control this invasive species.

Descended from the wild goat (C. aegagrus) self-perpetuating feral populations given their from central Asia (Zeder and Hesse 2000), ability to survive in a variety of habitats, on a domestic goats (Capra hircus) have been intro- wide variety of forage, and with limited water. duced to islands worldwide. The original pur- Goats have been considered by some to be pose of insular domestic goat introductions “the single most destructive herbivore” intro- was likely for sailors to populate oceanic is- duced to island ecosystems globally (King lands with a food source to access during later 1985:3). voyages (Campbell and Donlan 2005). Re- leased domesticated goats can quickly develop name

Capra hircus (Linnaeus, 1758) 1 Manuscript accepted 23 August 2012. This material Synonyms: Capra hircus, Capra hircus ae- is based upon work supported by the National Science gagrus, Capra aegagrus hircus. Foundation Graduate Research Fellowship under Grant Common names: briar goat, brush goat, No. 2010094953 (to M.W.C.); USDA Forest Service, feral goat, goat, hill goat, scrub goat, Spanish Pacific Southwest Research Station, Institute of Pacific Islands Forestry (Research Joint Venture 08-JV- goat, wood goat. 11272177-074 to C.M.L.); and the W. T. Yoshimoto Foundation Endowed Fellowship in Animal Wildlife description and account of variation Conservation Biology (to M.W.C.). Support to S.C.H. was provided by the USGS Invasive Species Program. 2 Department of Natural Resources and Environmen- Goats are even-toed hoofed ungulates of the tal Management, University of Hawai‘i at Mänoa, Hono- order Artiodactyla and have been considered lulu, Hawai‘i 96822. to comprise from one to nine species (Shack- 3 U.S. Geological Survey Pacific Island Ecosystems leton and Shank 1984 and references therein). Research Center, Hawai‘i National Park, Hawai‘i 96718. 4 Feral goats on Pacific islands (Figure 1) are U.S. Department of Agriculture Forest Service, In- stitute of Pacific Islands Forestry, Hilo, Hawai‘i 96720. assumed to have been introduced by Europe- 5 Corresponding author (e-mail: chynoweth.mark@ an sailors as a food source and are, therefore, gmail.com). most likely derived from continental Europe- an domestic goat breeds. Feral goats exhibit substantial intraspecific variation and are sex- Pacific Science (2013), vol. 67, no. 2:141 – 156 doi:10.2984/67.2.1 ually dimorphic. Generally, males are 20% © 2013 by University of Hawai‘i Press larger and have larger horns than females All rights reserved (Fleming 2004). Both males and females have

141 142 PACIFIC SCIENCE · April 2013

Figure 1. Feral goats, Capra hircus, on Hawai‘i Island. (Photo: Mark Chynoweth) horns made of living bone surrounded by etary preferences. In general ungulates, in- keratin. Goats typically weigh between 25 and cluding feral goats, demonstrate preference 55 kg, stand 1–1.2 m at the shoulder, and are and avoidance at least partly based on foliage 1–1.5 m long. All males and some females chemistry (Forsyth et al. 2002). McCammon- are bearded as adults. Both sexes have 30 –32 Feldman (1980) suggested that goats actively teeth, with upper and lower teeth in the back select the highest-quality forage. Although to chew cud and a dental pad in place of upper the most palatable forage is typically sought incisors. Goats sometimes resemble sheep out and consumed first, poor-quality forage but can be distinguished by their short, up- is often used to sustain populations (Coblentz ward pointing tails. Pelage coloration is typi- 1977, Green and Newell 1982). Consequent- cally black, but individuals can be white, ly, feral goats can extirpate preferred forage gray, brown, red, black, or any combination species (Coblentz 1977). thereof. Goats are often regarded as browsers. However, tendency to graze or browse is diet determined primarily by environmental conditions, such as seasonal and geographic vari- Feral goats are versatile generalist herbivores ation of forage. Instead, it may be more ap- capable of surviving on grasses, forbs, browse, propriate to classify goats as mixed feeding and even marine algae. Coblentz (1977) docu- opportunists (Lu 1988). As browsers, goats mented goats using almost every plant species are known to assume a bipedal stance to reach present within a study area in California. upper sections of shrubs and trees, and even However, feral goats demonstrate strong di- to climb into trees to access foliage. In the Pacific Island Invasive Species: Capra hircus, the Feral Goat · Chynoweth et al. 143 process of browsing, goats often strip bark the absence of nonnative ungulates (Merlin and girdle trees (Spatz and Mueller-Dombois and Juvik 1992). 1973). Removal of feral goats from entire islands, An important trait that enables feral goats or ungulate exclosures within islands, demon- to persist in arid island environments is their strates this transformative effect; native and remarkable ability to survive in the absence nonnative vegetation typically shows an im- of a permanent water source. Domestic goats mediate positive response to release from have a minimum water requirement of 1.0%– grazing and browsing pressure. Within fenced 1.5% body weight per day, but selective pres- units in dryland Hawaiian forests where goats sure may enable feral goats to survive in dry have been removed, native species demon- ecosystems with even less available water strate increased survival rates (Scowcroft and (Dunson 1974). Goats primarily derive pre- Hobdy 1987). On Hawai‘i Island, heavily formed water from plant foods in many sce- browsed areas demonstrate a lack of recruit- narios (Robbins 1994) but have also been ment and an older age class structure for the observed drinking salt water (Gould Burke dominant tree species, mämane (Sophora 1988). Limited water requirements have con- chrysophylla) (Scowcroft and Sakai 1983), and tributed to the success of feral goats as an in- reduced sucker growth on endemic koa (Aca- vasive mammal on numerous Pacific islands. cia koa) (Spatz and Mueller-Dombois 1973). On Guadalupe Island, Mexico, presumed ex- environmental impact and economic tinct and extirpated plant species have recov- importance ered from seed banks after goat removal (Keitt et al. 2005). Detrimental Aspects Foraging preferences of feral goats on Pa- cific islands vary greatly, depending largely on Nonnative feral goats are notorious for the composition of available plant communi- their negative impacts on island ecosystems ties. Goats are observed feeding on both na- (Coblentz 1978). Remote Pacific island plant tive and nonnative species, but native Pacific species evolved in geographic isolation from island plants are often consumed first because herbivorous mammals, losing many of the they lack defenses against herbivory and are, secondary chemical (e.g., tannins, turpenes) therefore, often more palatable. For this rea- and morphological (e.g., thorns) defense son, even low-density goat populations can mechanisms to deter herbivory (Kelsey and have negative consequences for native flora. Locken 1987, Bowen and Vuren 1997, Sheley In Hawai‘i Volcanoes National Park, D. K. and Petroff 1999). Consequently, native and Morris (unpubl. data) observed that stomach endemic plant communities are often unable contents of feral goats depended largely on to recover from persistent herbivory and density of animals present in an area. In areas trampling, resulting in their replacement by with low goat density, where native vegeta- more tolerant and resilient nonnative species tion was abundant, stomachs contained 98% (Augustine and McNaughton 1998). Intense native species. In contrast, nonnative plants browsing and grazing by goats can extirpate composed 99% of stomach contents in areas preferred species and cause the desertifica- of high goat density where native vegetation tion of entire islands. In some cases, such as was scarce. Although native species are often Santa Fe Island in the Galápagos, feral goats preferentially consumed when available, non- eliminated 100% of seedlings from large trees native plants support goat populations where (Clark and Clark 1981). Importantly, the native species do not occur. presence of nonnative ungulates can affect In addition to direct effects from browsing, competition between native and introduced grazing, and trampling, feral goats have implants. A comparison of Pacific islands with portant indirect effects; the alteration of plant and without introduced ungulates indicates communities through modification of plant that some island plant communities can more structure and destruction of habitat leads effectively resist nonnative plant invasions in to declining native wildlife populations, and 144 PACIFIC SCIENCE · April 2013 alteration of nutrient cycles (Zhang et al. Feral goats have been associated with the 2009, Gabay et al. 2011). These indirect ef- decline of native fauna because of habitat fects can lead to ecosystem state changes that modification as well as direct competition alter the function of an ecosystem. Notably, with native herbivores. Examples include the browsing and grazing can promote a cycle of Hawaiian goose (Branta sandvicensis) on Maui pyrogenic plant invasion and proliferation of ( Yocom 1967), as well as declines in popula- fine fuels leading to increased fire frequency tions of yellow-footed rock-wallabies (Petro- and severity (Cabin et al. 2000), thereby fa- gale xanthopus), brush-tailed rock-wallabies cilitating the conversion of tropical dry for- (Petrogale penicillata), mallee fowl (Leipoa ocel- ests to invasive grasslands (D’Antonio and lata), and the thick-billed grasswren (Amytor- Vitousek 1992). nis textilis) in Australia (Biodiversity Group Native island plant communities are par- 1998), and native jackrabbits (Lepus insularis) ticularly vulnerable to invasion by nonnative and woodrats ( Neotoma lepida) on Isla Es- plants ( Wilcove et al. 1998), which quickly píritu Santo, Mexico (León-de la Luz and occupy the available space created after goats Domínguez-Cadena 2006). In Hawai‘i, the remove native vegetation. The impacts of endangered palila (Loxioides bailleui), an en- nonnative herbivores differ between native demic finch-billed honeycreeper, relies pri- and exotic plant communities. Nonnative her- marily on the native mämane tree (Sophora bivores are known to facilitate both the abun- chrysophylla) as a food source (Banko et al. dance and species richness of nonnative plants, 2009). Nonnative ungulates, including pri- whereas native herbivores often suppress marily goats and sheep, have heavily browsed nonnative plants (Parker et al. 2006, Oduor et and degraded mämane forest habitat, where al. 2010). These impacts include dispersal of they prefer accessible foliage, saplings, and both nonnative and native plant seeds via ex- bark of mature trees as forage (Scowcroft and crement and attachment to fur ( Janzen 1984), Sakai 1983). In addition, the removal of feral and trampling of plants on paths, wallows, goats has led to the recovery of endangered and in resting beds. Nonnative plant species fauna, such as the Galápagos rail (Laterallus can often quickly replace native plants as a di- spilonotus) on Santiago Island (Donlan et al. rect or indirect result of nonnative ungulates 2007), and increased ability for reintroduc- by overwhelming seed banks and manifesting tions and conservation introductions to occur pioneer traits (Sheley and Petroff 1999). (Bellingham et al. 2010). These effects can be enhanced or reduced In addition to ecological impacts, feral with extreme weather events such as drought goats pose several potential problems for do- or enhanced precipitation. mestic livestock populations (Heath et al. Following intense grazing and trampling 1987). Feral goats may introduce novel patho- of goats on islands, erosion can occur (Co- gens or act as a reservoir for existing diseases blentz 1978). Goats can remove 6 kg/day of and parasites (Hein and Cargill 1981). For ex- dry matter compared with 3.8 kg/day for ample, in New Zealand feral goats have been sheep and 2.9 kg/day for cattle (Thornes 1985 found to carry 22 nematode, two cestode, two and references therein). Once vegetation is trematode, four arthropod, and three proto- removed, erosion can occur rapidly with pre- zoan parasites (Parkes et al. 1996). Disease cipitation, wind, and further disturbance via and parasite transmission to domestic popula- goat movement. Yocom (1967) speculated tions could occur either in pasture areas or if that approximately 1.9 m of topsoil disap- feral populations are gathered and driven to peared as a result of goat activity on Haleakalä slaughter. Zoonotic diseases such as tubercu- Crater on the island of Maui. As such, over- losis, brucellosis, and rabies are potentially grazing by goats can contribute to massive transferable to humans (Smith and Sherman erosion and subsequent runoff that can dam- 1994). Feral goats also compete with domestic age nearshore marine ecosystems, as in the livestock for forage and contribute to overall case of Kaho‘olawe Island, Hawai‘i (Loague degradation of rangelands (Thompson et al. et al. 1996). 2002). Pacific Island Invasive Species: Capra hircus, the Feral Goat · Chynoweth et al. 145

Beneficial Aspects tantly, nonnative ungulates are a known critical barrier to native species conservation and Economically, the goat may be more valuable restoration efforts, and the ecological benefits to the world’s agricultural system than any of feral goat populations on Pacific islands are other animal species (Dunbar 1984). Domes- very few. tic goats are one of the primary livestock spe- Although direct benefits are not often cies in the developing world used for both seen from goat presence, it is possible that na- dairy and meat, but domestic goat dairy prod- tive species could benefit from goat presence ucts also provide for special dietary needs in by moving nutrients from inaccessible areas developed regions. Feral goats represent a through fertilization via feces (Gould and major source of meat and skins. In the past, Swingland 1980). However, it can also be as- feral goat populations were harvested from sumed that exotic plant species dispropor- Pacific islands for the goat skin trade ( Yocom tionately benefit from this same process, and 1967), but Australia has become a leader in often respond much faster (Funk and Vi- the industry more recently. In Australia, feral tousek 2007, Ostertag et al. 2009). In some goats continue to be harvested for both com- cases, an initial rapid spread of introduced mercial enterprise and conservation objec- species has occurred following nonnative un- tives (Ramsay 1994, Forsyth et al. 2003). gulate eradication (Kellner et al. 2011, Kes- In addition to limited commercial value on sler 2011), but some invasions have also stabi- islands, feral goats also have recreational, sub- lized over longer periods of time, benefiting sistence, and cultural value for some Pacific native biota (Kessler 2011). Limited examples islanders. Feral goats are harvested as a source also exist where native fauna may experience of meat and provide a small number of em- benefits from goat presence. Desender et al. ployment opportunities through hunting out- (1999) observed an increase in the diversity fitters. There are divergent societal views re- of xerophilic terrestrial invertebrates in the garding the value of feral goats, with some Galápagos as a result of goat grazing due to a individuals and groups regarding these ani- temporary increase in habitat heterogeneity. mals as a sustained-yield hunting resource Both domestic and feral goats have often and others regarding them as an undesirable been used for biological control of weeds, im- pest (Hess and Jacobi 2011, Kessler 2011). To provement to ranges (Sakanoue et al. 1995, address these issues related to conservation Goehring et al. 2010), and even for the con- and ecological restoration, decision analysis trol of control brush in fuel breaks (Green and can be used to incorporate social values and Newell 1982). Domestic goat breeds, such as stakeholder preferences into management Angora or Nubian, can provide mohair and strategies (Maguire 2004). milk, respectively, while simultaneously im- Ecologically, although often considered proving rangelands or controlling weeds. Al- negative, long-term impacts of feral goats on though feral goats can be used for the same Pacific islands are not always straightforward purposes, small-scale prescribed or targeted (Cabin et al. 2000). In highly modified ecosys- grazing and browsing by domestic animals tems, such as heavily invaded tropical dry for- typically yield better results (Green and ests, removal of generalist herbivory by feral Newell 1982). goats has been shown to facilitate the short- term proliferation of invasive plants (Kellner geographic distribution in the pacific et al. 2011). Long-term studies on the effects region of ungulate exclusion indicate that animal removal can also release invasive pyrogenic The geographic distribution of the feral goat grasses from top-down control (Cabin et al. in the Pacific region includes essentially all 2000). However, when invasive grasses are islands that have suitable habitat (Table 1). controlled after ungulate removal, an increase Goats have been deliberately introduced to in natural regeneration of native plants has most islands, and these introductions have been observed (Thaxton et al. 2010). Impor- failed only on atolls (e.g., Kiribati and Tuvalu 146 PACIFIC SCIENCE · April 2013

TABLE 1 [see Hussain 1987]). Goats have been eradi- Presence of Feral Goats on Select Pacific Islands cated to maintain watershed function and protect native species on numerous islands Pacific Islands Present Absent Notes (e.g., Läna‘i in Hawai‘i, Santiago in the Galá- pagos [Keitt et al. 2011]). American Samoa x Australia x Bonin Islands x Archipelago-wide habitat eradication program is in The remarkable adaptability of goats as a spe- progressa cies has enabled feral populations to establish Cocos Islands x themselves across a wide range of habitats Cook Islands x Easter Island x Domestic goats throughout the Pacific. Goats demonstrate a present wide range of physiological capabilities that Fiji x allow them to survive in a variety of tempera- French Polynesia x tures, altitudes, and habitats (Shackleton and Galápagos x Archipelago-wide Shank 1984). Few factors limit their distribu- Islands eradication program is in tion, such as deep snow, tundra, and desert progressb habitats. However, feral goats generally ap- Guam x pear to prefer xeric grasslands and high topo- Hawaiian Islands x graphic variability (Shackleton and Shank Indonesia x Japan x 1984). Juan Fernández x On Pacific islands, feral goat populations Islands exist from low to high elevations and in xeric Kiribati x Introduced, but to mesic habitats (Stone 1985). As opportu- failed nistic herbivores, feral goats use an assort- Marshall Islands x Introduced, but failedc ment of forage for subsistence, including na- Micronesia x tive and nonnative plants ( Yocom 1967, Baker Nauru x and Reeser 1972). Preferred feeding areas ap- New Caledonia x pear to be open, dry grasslands, shrublands, New Zealand x Niue x or forests (Morris 1969, cited in Baker and Norfolk Island x Eradicated in Reeser 1972). However, goats can be ob- 1856 served in nearly every tropical insular habitat. Northern x The majority of native plant communities on Mariana islands are heavily invaded and subsequently Islands Palau x Domestic goats impacted by feral goat populations in some present manner. Papua New x Guinea history of introductions Philippines x Pitcairn Island x Solomon Islands x Domestic goats Domestic goats have arguably been intention- present ally introduced to more islands worldwide Taiwan x than any other mammal with the possible ex- Tokelau Island x Introduced but ception of domestic cats (Duffy and Capece failedc Tonga x 2012). Goats have been introduced to all Tuvalu x Introduced but continents (except Antarctica) and can inhabit failed a range of climates and conditions. Their Vanuatu x unique ability to survive on a wide variety of Wake Island x Wallis and x Domestic goats forage and limited water supply made them Futuna present ideal candidates for food supplies on remote and arid islands. In addition to intentional a Yoshikazu Shimizu, pers comm. b Carrion et al. (2011). introductions, domesticated goats have also c Alik et al. (2010). Pacific Island Invasive Species: Capra hircus, the Feral Goat · Chynoweth et al. 147 repeatedly escaped captivity to establish feral observed to occur in groups of up to 200, at populations. least temporarily (M.W.C., pers. obs.). Three The earliest known introduction to an oce- types of herds usually exist: (1) all males anic island was that of St. Helena in 1513 ( bachelor herds); (2) mixed sex and age (Dunbar 1984). In the Pacific region, the Juan groups; and (3) females and young. Frequent Fernández Islands may have had the first fission and fusion occur throughout the day known introduction, in the sixteenth century as goats travel through their home range in ( Wester 1991). Most renowned for his role in search of forage. Average home range size dif- goat introductions was Captain Cook, who fers significantly between males and females, was responsible for releasing goats in New and also between geographic areas and re- Zealand, Hawai‘i, and many smaller islands in source availability (O’Brien 1984a). Estimates the South Pacific during the late eighteenth range from 0.4 –5.3 km2 on Aldabra Island century (Tomich 1986). In other locations, (Gould Burke 1988) to 139.2–587.7 km2 in goats were imported to control brush or for Australia (King 1992). Although some social the agricultural industry, only to escape cap- characteristics vary between populations, tivity and establish feral populations. Goat others are more common. Group size, group introductions are not well documented be- composition, home range variations, sexual cause it was common practice to carry these segregation, and use of permanent night animals aboard ships and release them as a fu- camps are all common characteristics among ture food source. Shipwrecks could also have populations (O’Brien 1988). released goats onto oceanic islands (Dunbar Goats have excellent eyesight with a pan- 1984). oramic field view of 320°–340°. Their unique Only on small oceanic atolls with very rectangular pupil, common to other ungu- limited resources have goat populations failed lates, enables increased peripheral depth per- to become established. In some cases, goat ception (Abbott 1907). Furthermore, tests on populations have crashed due to overbrows- male goats indicate capacity for color vision ing and desertification. However, this evi- (Buchenauer and Fritsch 1980). Feral goats dence should be considered circumstantial also possess an acute sense of hearing and are because goats may often be the only animal able to direct their ears toward a source of present during the final stages of land cover sound. Likewise, their sense of smell is well change (Dunbar 1984). It is interesting that developed and is often used to evaluate po- isolation on islands has caused some feral tential food items. Feral goats make several goat populations to experience substantial distinct vocalizations ( bleating) related to genetic drift. In some cases, such as San offspring, danger, and agonistic behavior. Clemente Island, California, domestic live- Mothers and offspring are able to locate each stock that are derived from feral popula- other based on these auditory cues (Ruiz- tions may be recognized as a unique heritage Miranda et al. 1993). breed by the American Livestock Breeds Physiologically, goats have a mean body Conservancy. temperature of 38.6°C–39.7°C, resting heart rate of 70 –90 beats per minute, respiration physiology and behavior rate of 12–20 breaths per minute, and a life span of 10 –12 yr ( Nowak and Paradiso 1983). Feral goats are well adapted to survive in a As ruminants, goats have a four-chambered wide variety of conditions, exhibiting a suite stomach consisting of rumen, reticulum, of behaviors that are remarkably similar to omasum, and the abomasums. As goats con- those of conspecific domesticates. Goats are sume grasses and forbs (grazing) as well as social animals that prefer traveling in herds shrubs and trees ( browsing), the muscular (i.e., tribe or trip), with a modal group size of and microbial action of the rumen physically two to four animals (O’Brien 1988). Large and chemically breaks down nutrients at 1– herds of up to 100 individuals are not un- 1.5 ruminal movements per minute ( North common. In Hawai‘i feral goats have been 2004). 148 PACIFIC SCIENCE · April 2013

reproduction Following parturition, females either leave or stay with kids for a brief lying-out phase Breeding systems of feral goats are highly (O’Brien 1984b), often in a protected shaded variable, ranging from year-round breeding location (O’Brien 1983) followed by a crèche in Hawai‘i (Ohashi and Schemnitz 1987) (i.e., nursery group) formation in some herds and New Zealand (Rudge 1969) to season- (O’Brien 1988). Females accompanied by kids ally polyestrous breeding cycles in more- often separate themselves from other adults temperate latitudes (Turner 1936, Asdell to reduce competition for resources (Calhim 1964). Reproductive cycles vary greatly, be- et al. 2006). Offspring begin to feed them- cause females have the ability to come into selves after 2–3 weeks but remain close to estrus year-round (Phillips et al. 1943). Co- their mother until approximately 6 months, blentz (1980) observed quadrimodal birth when they either remain with the family pulses on Santa Catalina Island, for which group or join another herd. the proximate cause was unknown. Males appear to be able to bring females into es- population dynamics trous, but number of ruts throughout the year may ultimately depend on environmental Reproductive abilities of feral goats enable conditions. rapid population growth, particularly in is- Goats typically reach sexual maturity at 6 land ecosystems where competition and pre- months of age (Ohashi and Schemnitz 1987), dation are typically minimal. Watts and Con- with young females typically entering breed- ley (1984:814) stated that “the combination of ing stage immediately, but young males are an early initial breeding stage, short gestation, often outcompeted by older, more experi- postpartum estrus, high breeding rate, and enced males. Operational and actual sex ratios twinning allow goat populations to achieve are usually female biased (O’Brien 1988, annual growth rates of 10 –35%.” Hence, Keegan et al. 1994). During the rut, a buck population doubling times can be as low as 2.3 releases an oily substance with a strong to 7.3 yr ( Watts and Conley 1984). This rapid scent to attract females. This type of scent- growth rate needs to be considered in man- urination is a form of communication for both agement of these animals, because Rudge and males and females (Coblentz 1976) during Smith (1970) predicted that a population re- flehmen (open mouth, curled back lip) behav- duced by 80% could potentially recover to ior involved in olfactory perception of this 90% of the original level in 4 yr. and other compounds (O’Brien 1982). As in Feral goat densities on Pacific islands de- many social ungulates, males compete for fe- pend on a variety of factors, including envir- males in estrus. However there is some evi- onmental conditions and level of animal con- dence that females have substantial control trol. In harsh atoll conditions, densities can over which male with whom they choose to be as low as five to eight goats per square kilo- breed (Margiasso et al. 2010). Males demon- meter (Burke 1987). In favorable conditions, strate two principal mating techniques: tend- such as those on Macauley Island, New Zea- ing, where a dominant male defends estrus land, densities have reportedly reached as high females, or coursing, where males of all ages as 400 goats per square kilometer ( Nowak and attempt to disturb a tending pair (Saunders Paradiso 1983). Goat populations can expand et al. 2005). rapidly under favorable environmental con- Gestation period is approximately 150 days ditions, making these animals formidably in- ( Yocom 1967), with twinning being common vasive on Pacific islands. (Rudge 1969). Where environmental condi- Isolated island populations of feral goats tions are favorable, females may give birth are quite variable in many aspects, which may twice a year (Ohashi and Schemnitz 1987). In be related to small initial introductions from New Zealand, average live weight for female which those populations were derived. Gould kids is 4.6 ± 0.7 kg, and average live weight (1979) observed variation in color, body size, for male kids is 5.7 ± 1.1 kg (Kirton 1977). reproductive rate, population size, water bal- Pacific Island Invasive Species: Capra hircus, the Feral Goat · Chynoweth et al. 149 ance, and behavior between two isolated pop- mate goal is eradication, public hunting by ulations separated by water on Aldabra Island. recreational and subsistence hunters can be Variations in genetics and behavior may be a ineffective, because hunters often select for combination of a founder effect and the vari- trophy-quality males and can shift the sex able environmental conditions of islands that ratio, leading to increased population growth feral goats inhabit. However, over the past (Stephens et al. 2008). Although helicopter few centuries, additional introductions may activity does not appear to cause long-term have reduced the founder effect. behavioral changes, short-term effects occur frequently (Tracey and Fleming 2007). Goats management with previous exposure to aerial hunting via helicopter are twice as likely to exhibit evasive By the mid-twentieth century, many biolo- activity (Bayne et al. 2000). gists had come to a consensus on the negative Toxicants have been briefly explored as an impacts of feral ungulates on islands (Co- option for population control. Limitations ex- blentz 1978) and began developing techniques ist due to effects on nontarget species and the to remove goat populations from them (Daly ability to distribute baits across the range of 1989). Strategies to manage goats include tak- an entire goat population. Aerially distributed ing no action, eradication, annual control in baits are not considered effective because feral perpetuity, or occasional control in perpetuity goats do not often eat from the ground (For- (Parkes 1990). In many areas, such as Halea- syth and Parkes 1995). Although sodium flu- kalä National Park in Hawai‘i, intense goat oroacetate (1080) is not a registered toxicant control programs have occurred sporadically for goat control in New Zealand, Veltman since the early twentieth century, with active and Parkes (2002) suggested that it might be hunting numbering 10,000 person-days over useful for high-density goat populations in four decades (Kjargaard 1984). Due to their areas that are inaccessible to ground or aerial large physical size and gregarious behavior, hunting. feral goats are an ideal candidate for success- Biological control of goats is unlikely, be- ful eradications on small to midsized islands. cause both pathogens and predators are not Worldwide, >95% of 165 eradication at- target-specific, posing considerable risks to tempts on islands have been successful (Keitt livestock populations. Goats have no natural et al. 2011), and goats have been removed predators on Pacific islands. Feral goat popu- from more than 1,360 km2 in the central Pa- lations may experience minimal predation cific region alone. The largest land area from from feral dogs (Canis lupus familiaris) and which goats have been eradicated on any Pa- golden eagles (Aquila chrysaetos). One example cific island was the 585 km2 Galápagos island exists of successful biological control using of Santiago, Ecuador, in 2005 (Cruz et al. dingoes (Canis lupus dingo) on Townshend Is- 2009). However, a highly technical eradica- land (L. Allen and J. Lee, unpubl. data). How- tion from 554 km2 of Hawai‘i Volcanoes ever, large predators are not suitable for most National Park on the island of Hawai‘i was areas, because they pose serious potential accomplished in 1984, requiring perimeter risks to livestock, native fauna, and humans. fences to exclude adjacent populations (Hess Judas goats are one of the most effective and Jacobi 2011). tools to aid in eradication efforts. Judas ani- Trapping, hunting, poisoning, biocontrol, mals are individual goats, typically female, or any combination thereof can be used to equipped with a telemetry collar used to eradicate populations of invasive mammals locate remnant herds (Taylor and Katahira ( Veitch and Clout 2002). All techniques have 1988). Finding collared individuals will lead been used on goats; however the most com- to another herd because goats are highly mon method is hunting. Tools to aid in hunt- social animals. As each herd is eliminated, ing efforts include dogs, aerial hunting from collared animals are spared to find addi- helicopters, exploiting the social behavior of tional herds. On San Clemente Island in Cali- goats, and utilizing local hunters. If the ulti- fornia, Judas goats were able to locate other 150 PACIFIC SCIENCE · April 2013 indi viduals within their maximum search target animals from an entire island, regard- range within 3 days of eradication of the rest less of island size. of the herd (Keegan et al. 1994). All animals Fencing and eradication of ungulates from can be removed using this method (Rainbolt ecologically sensitive areas have been impor- and Coblentz 1999). tant steps in conservation and restoration; Judas goats can also have their reproduc- however, most disturbed sites require contin- tive systems manipulated to increase efficacy. ual monitoring and specific alien plant man- Methods to sterilize goats, including tubal agement strategies after ungulates have been occlusion and epididymectomy can be ac- eliminated. Invasions of nonnative plant spe- complished in the field (Campbell et al. 2005). cies have occurred in areas where animals Female Judas goats can be further modified to have been removed (Kessler 2002, Kellner become Mata Hari goats, by inducing either et al. 2011), but some invasive species have prolonged duration or increased frequency stabilized over time (Kessler 2011). In a study of estrus (Campbell 2007, Campbell et al. of 50 ungulate exclosures throughout Hawai‘i, 2007). Numerous males may be repeatedly at- native biota held their own or increased after tracted by implanting hormones in females to removal of ungulate damage in most situa- heighten estrous periods. tions; however, the chance of recovery be- Removal of all animals is necessary for suc- came reduced as the extent of degradation cessful eradication; a small number of failed increased (Loope and Scowcroft 1985). Dam- eradication attempts have resulted from the age by nonnative ungulates precipitated large- recovery of few remaining animals because of scale invasion of alien plant species. Displace- high reproductive rates (Parkes 1984). Use of ment by alien grasses appeared to be the most multiple techniques and technology such as important factor inhibiting reproduction of global positioning systems (GPS), geographic native species in areas other than rain forest. information systems (GIS), remote sensing, Comparative studies suggest that some plant and forward-looking infrared radar are help- communities recover better than others after ful for successful eradication of goats on is- ungulate disturbance is curtailed (Stone et al. lands. Immigration and recolonization may 1992). Remote, lightly disturbed rain forest, occur if barriers are not adequate to exclude coastal strand, ‘öhi‘a (Metrosideros polymorpha), nearby goats. In New Zealand, a population and native subalpine bunchgrass and shrub recovered 30%– 40% of the original size in 10 are among the least affected by long-term months due to immigration (Brennan et al. disturbance by goats and other ungulates in 1993). Hawai‘i. On many larger islands, goat populations have been excluded from distinct manage- prognosis ment areas, particularly management areas with high densities of native species and /or Capra hircus populations are present on is- native species populations of conservation lands throughout the Pacific and remain a se- concern. Fences have been built around sensi- rious threat to native flora and fauna, as well tive ecosystems to exclude goats from an area, as a critical barrier to conservation and eco- which is technically difficult but more fea- logical restoration. Most important, it should sible than island-wide eradication from multi- be recognized that feral goats have a substan- tenure islands (Campbell and Donlan 2005). tial impact on ecosystem structure and need Fence construction can be a costly manage- to be controlled or eliminated to accomplish ment technique requiring continual monitor- most, if not all, conservation goals that in- ing, maintenance, and cyclical replacement to clude restoration of native plant communities. prevent ingress; however, it is an important The combination of both being a generalist first step toward native species restoration at a and having the ability to thrive in arid envi- broad landscape scale. Given the costs of con- ronments makes goats a formidable invasive trolling populations in perpetuity, it is more species on Pacific islands. Although tech- cost-effective in the long term to eradicate all niques and technology for eradication have Pacific Island Invasive Species: Capra hircus, the Feral Goat · Chynoweth et al. 151 been developed and proven effective, resource islands novel ecosystems have emerged that constraints and conflicting societal values have no natural analog and are increasingly limit the success of goat management, mak- managed as a mix of native and nonnative spe- ing eradication on many larger multitenure cies (hybrid ecosystems). Removal of goats islands challenging (Campbell and Donlan from these novel and hybrid ecosystems is a 2005). Ungulate removal is often considered critical first step, but management activities an essential first step in conservation and res- that include monitoring and control of other toration of native ecosystems on most Pacific invasive species are essential to maintain bio- islands. The construction of barrier fences diversity and ecosystem structure. Monitor- and eradication of feral goats by ground and ing ecosystem structure and function before, aerial hunting, coupled with the use of telem- during, and after goat management will help etry and other technologies, have been the land managers understand the role of goats in primary tools that have proven successful on shaping emerging island ecosystems and will islands throughout the world. guide a management approach to better con- Given the recent gains in knowledge, tech- serve native species on Pacific islands. nological advances, and logistical experience in nonnative mammal eradication, biological acknowledgments limitations to feral goat control no longer exist. In addition, research overwhelmingly sup- We thank K. Campbell and an anonymous re- ports the removal of these animals to achieve viewer for many helpful comments. Any use conservation and restoration goals in native of trade, product, or firm names in this publi- island ecosystems. These ecosystems repre- cation is for descriptive purposes and does not sent major holdings of global biodiversity and imply endorsement by the U.S. Government. are currently experiencing a disproportion- ately high number of extinctions (Keitt et al. Literature Cited 2011). As more resources are allocated to conservation and restoration of island eco- Abbott, W. J. 1907. Experiments on the func- systems, goat eradications will continue on tion of slit-form pupils. Pages 71–84 in islands of all sizes, including enclosed areas on University of Toronto Studies: Psycho- multitenure islands. Larger and more techni- logical Series. University of Toronto, To- cal projects will incorporate next-generation ronto. tools (e.g., advancements in GPS, GIS, and Alik, T., B. V. Velde, and N. V. Velde. 2010. remote sensing) to execute effective feral goat Ruminant livestock on central Pacific removal plans. However, it is important to atolls: The potential implications of soil on recognize that management of native island herbivorous animal survival and possible ecosystems will not typically end with goat implications for agriculture and human eradication but rather will entail a long-term health. Atoll Res. Bull. 580:1–18. commitment to control of other nonnative Asdell, S. A. 1964. Patterns of mammalian invasive species, along with active manage- reproduction. 2nd ed. Cornell University ment of native species of conservation con- Press, Ithaca, New York. cern (Cole et al. 2012). Augustine, D. J., and S. J. McNaughton. Feral goats undoubtedly have had a nega- 1998. Ungulate effects on the functional tive impact on native island ecosystems, but species composition of plant communities: their long history on Pacific islands and their Herbivore selectivity and plant tolerance. impact on ecosystem structure and function J. Wildl. Manage. 62:1165–1183. should not be overlooked. As Cabin et al. Baker, J. K., and D. W. Reeser. 1972. Goat (2000) suggested, feral ungulates may play an management problems in Hawai‘i Volca- important role in nonnative species control in noes National Park. National Park Service limited circumstances, notably in highly de- Natural Resources Report. No. 2. graded ecosystems that already have large Banko, P. C., K. Brink, C. Farmer, and S. nonnative plant populations. On many Pacific Hess. 2009. Recovery programs: Palila. 152 PACIFIC SCIENCE · April 2013

Pages 513–533 in T. K. Pratt, C. T. Atkin- sation, abortion, hormone implants and son, P. C. Banko, J. D. Jacobi, B. L. epididymectomy. Ph.D. diss., University Woodworth, eds. Conservation biology of of Queensland, Gatton, Australia. Hawaiian forest birds: Implications for is- Campbell, K. J., G. S. Baxter, P. J. Murray, land avifauna. Yale University Press, New B. E. Coblentz, and C. J. Donlan. 2007. Haven. Development of a prolonged estrus effect Bayne, P., B. Harden, K. Pines, and U. Tay- for use in Judas goats. Appl. Anim. Behav. lor. 2000. Controlling feral goats by shoot- Sci. 102:12–23. ing from a helicopter with and without the Campbell, K. J., G. S. Baxter, P. J. Murray, assistance of ground-based spotters. Wildl. B. E. Coblentz, C. J. Donlan, and V. Car- Res. 27:517–523. rion. 2005. Increasing the efficacy of Judas Bellingham, P. J., D. R. Towns, E. K. Cam- goats by sterilisation and pregnancy termi- eron, J. J. Davis, D. A. Wardle, J. M. nation. Wildl. Res. 32:737–743. Wilmshurst, and C. P. H. Mulder. 2010. Campbell, K., and C. J. Donlan. 2005. Feral New Zealand island restoration: Seabirds, goat eradications on islands. Conserv. Biol. predators, and the importance of history. 19:1362–1374. N. Z. J. Ecol. 34:115–136. Carrion, V., C. J. Donlan, K. J. Campbell, C. Biodiversity Group. 1998. Threat abatement Lavoie, and F. Cruz. 2011. Archipelago- plan for competition and land degradation wide island restoration in the Galápagos by feral goats. Department of the En- Islands: Reducing costs of invasive mam- vironment, Water, Heritage, and the Arts, mal eradication programs and reinvasion Canberra. risk. PloS One 6: e18835. Bowen, L., and D. Van Vuren. 1997. Insular Clark, D. A., and D. B. Clark. 1981. Effects endemic plants lack defenses against herbi- of seed dispersal by animals on the regen- vores. Conserv. Biol 11:1249–1254. eration of Bursera graveolens (Burseraceae) Brennan, M., H. Moller, and J. P. Parkes. on Santa Fe Island, Galápagos. Oecologia 1993. Indices of density of feral goats in a (Berl.) 49:73–75. grassland forest habitat, Marlborough, Coblentz, B. E. 1976. Functions of scent- New Zealand. N. Z. J. Ecol. 17:103–106. urination in ungulates with special refer- Buchenauer, V. D., and B. Fritsch. 1980. ence to feral goats (Capra hircus L.). Am. Color-vision in domestic goats (Capra Nat. 110:549–557. hircus L.). Z. Tierpsychol. 53:225–230. ———. 1977. Some range relationships of Burke, M. B. 1987. The mating system of feral goats on Santa Catalina Island, Cali- tropical feral goats, social organization, sex fornia. J. Range Manage. 30:415– 419. ratios and population dynamics. Am. Zool. ———. 1978. The effects of feral goats ( Capra 27:A28–A28. hircus) on island ecosystems. Biol. Conserv. Cabin, R. J., S. G. Weller, D. H. Lorence, 13:279–286. T. W. Flynn, A. K. Sakai, D. Sandquist, ———. 1980. A unique ungulate breeding and L. J. Hadway. 2000. Effects of a long- pattern. J. Wildl. Manage. 44:929–933. term ungulate exclusion and recent alien Cole, R. J., C. M. Litton, M. J. Koontz, and species control on the preservation and R. K. Loh. 2012. Vegetation recovery restoration of a Hawaiian tropical dry 16 years after feral pig removal from a forest. Conserv. Biol. 14:439– 453. wet Hawaiian forest. Biotropica 44:463– Calhim, S., J. Shi, and R. I. M. Dunbar. 2006. 471. Sexual segregation among feral goats: Cruz, F., V. Carrion, K. J. Campbell, Testing between alternative hypotheses. C. Lavoie, and C. J. Donlan. 2009. Bio- Anim. Behav. 72:31– 41. economics of large-scale eradication of fe- Campbell, K. J. 2007. Manipulation of the ral goats from Santiago Island, Galápagos. reproductive system of feral goats (Capra J. Wildl. Manage. 73:191–200. hircus) to increase the efficacy of Judas Daly, K. 1989. Eradication of feral goats from goats: Field methods utilising tubal sterili- small islands. Oryx 23:71–75. Pacific Island Invasive Species: Capra hircus, the Feral Goat · Chynoweth et al. 153

D’Antonio, C. M., and P. M. Vitousek. 1992. Goehring, B. J., K. L. Launchbaugh, and Biological invasions by exotic grasses, the L. M. Wilson. 2010. Late-season targeted grass/fire cycle, and global change. Annu. grazing of yellow starthistle (Centaurea sol- Rev. Ecol. Syst. 23:63–87. stitialis) with goats in Idaho. Invasive Plant Desender, K., L. Baert, J. Maelfait, and P. Sci. Manage. 3:148–154. Verdyck. 1999. Conservation on Volcán Gould, M. 1979. The behavioural ecology Alcedo (Galápagos): Terrestrial inverte- of the feral goats of Aldabra Island. Ph.D. brates and the impact of introduced feral diss., Duke University, Durham, North goats. Biol. Conserv. 87:303–310. Carolina. Donlan, C. J., K. Campbell, W. Cabrera, C. Gould Burke, M. 1988. The feral goats of Al- Lavoie, V. Carrion, and F. Cruz. 2007. Re- dabra: Ecology and population dynamics. covery of the Galápagos rail (Laterallus spi- Natl. Geogr. Res. 4:272–279. lonotus) following the removal of invasive Gould, M., and I. Swingland. 1980. The tor- mammals. Biol. Conserv. 138:520 –524. toise and the goat: Interactions on Aldabra Duffy, D. C., and P. Capece. 2012. Biology Island. Biol. Conserv. 17:267–279. and impacts of Pacific island invasive spe- Green, L. R., and L. A. Newell. 1982. Using cies. 7. The domestic cat (Felis catus). Pac. goats to control brush regrowth on fuel- Sci. 66:173–212. breaks. U.S. For. Serv. Gen. Tech. Rep. Dunbar, R. 1984. Scapegoat for a thousand PSW-59. deserts. New Sci. 104:30 –33. Heath, A. C. G., J. D. Tenquist, and D. M. Dunson, W. A. 1974. Some aspects of salt and Bishop. 1987. Goats, hares, and rabbits water balance of feral goats from arid is- as hosts for the New Zealand cattle tick, lands. Am. J. Physiol. 226:662– 669. Haemaphysalis longicornis. N. Z. J. Zool. Fleming, P. J. S. 2004. Relationships between 14:549–555. feral goats (Capra hircus) and domestic Hein, W. R., and C. F. Cargill. 1981. An abat- sheep (Ovis aries) with reference to exotic toir survey of diseases of feral goats. Aust. disease transmission. Ph.D. diss., Univer- Vet. J. 57:498–503. sity of Canberra, Bruce, ACT. Hess, S. C., and J. D. Jacobi. 2011. The his- Forsyth, D. M., D. A. Coomes, G. Nugent, tory of mammal eradications in Hawai‘i and G. M. J. Hall. 2002. Diet and diet pref- and the United States associated islands erences of introduced ungulates (Order: of the central Pacific. Pages 67–73 in C. R. Artiodactyla) in New Zealand. N. Z. J. Veitch, M. N. Clout, and D. R. Towns, Zool. 29:323–343. eds. Island invasives: Eradication and man- Forsyth, D. M., J. Hone, J. P. Parkes, G. H. agement. IUCN, Gland, Switzerland. Reid, and D. Stronge. 2003. Feral goat Hussain, M. Z. 1987. Goat development on control in Egmont National Park, New atolls in the Pacific: Kiribati and Tuvalu Zealand, and the implications for eradica- experience. Agric. Serv. Bull. (F.A.O.) tion. Wildl. Res. 30:437– 450. 12:99–105. Forsyth, D. M., and J. P. Parkes. 1995. Suit- Janzen, D. H. 1984. Dispersal of small seeds ability of aerially sown artificial baits as by big herbivores: Foliage is the fruit. Am. a technique for poisoning feral goats. Nat. 123:338–353. N. Z. J. Ecol. 19:73–76. Keegan, D. R., B. E. Coblentz, and C. S. Funk, J. L., and P. M. Vitousek. 2007. Winchell. 1994. Feral goat eradication on Resource-use efficiency and plant invasion San Clemente Island, California. Wildl. in low-resource systems. Nature (Lond.) Soc. Bull. 22:56 – 61. 446:1079–1081. Keitt, B., K. Campbell, A. Saunders, M. Gabay, O., A. Perevolotsky, A. BarMassada, Clout, Y. Wang, R. Heinz, K. Newton, Y. Carmel, and M. Shachak. 2011. Differ- and B. Tershy. 2011. The global islands ential effects of goat browsing on herba- invasive vertebrate eradication database: A ceous plant community in a two-phase mo- tool to improve and facilitate restoration saic. Plant Ecol. 212:1643–1653. of island ecosystems. Pages 74 –77 in C. R. 154 PACIFIC SCIENCE · April 2013

Veitch, M. N. Clout, and D. R. Towns, León-de la Luz, J. L., and R. Domínguez- eds. Island invasives: Eradication and man- Cadena. 2006. Herbivory of feral goats on agement. IUCN, Gland, Switzerland. Espiritu Santo Island, Gulf of California, Keitt, B., S. Junak, L. L. Mendoza, and A. Mexico. Smithson. Contrib. Bot. 22:1135– Aquirre. 2005. The restoration of Guada- 1143. lupe Island. Fremontia 33:20 –25. Loague, K., D. Lloyd, T. W. Giambelluca, S. Kellner, J. R., G. P. Asner, K. M. Kinney, Nguyen, and B. Sakata. 1996. Land misuse S. R. Loarie, D. E. Knapp, T. Kennedy- and hydrologic response: Kaho‘olawe, Bowdoin, E. J. Questad, S. Cordell, and Hawai‘i. Pac. Sci. 50:1–35. J. M. Thaxton. 2011. Remote analysis of Loope, L. L., and P. G. Scowcroft. 1985. biological invasion and the impact of ene- Vegetation response within exclosures in my release. Ecol. Appl. 21:2094 –2104. Hawai‘i: A review. Pages 377– 402 in C. Kelsey, R. G., and L. J. Locken. 1987. Phyto- Stone and J. Scott, eds. Hawai‘i’s terres- toxic properties of cnicin, a sesquiterpene trial ecosystems: Preservation and manage- lactone from Centaurea maculosa (Spotted ment. University of Hawai‘i Press, Hono- Knapweed). J. Chem. Ecol. 13:19–33. lulu. Kessler, C. C. 2002. Eradication of feral goats Lu, C. 1988. Grazing behavior and diet selec- and pigs and consequences for other biota tion of goats. Small Ruminant Res. 1:205– on Sarigan Island, Commonwealth of the 216. Northern Mariana Islands. Pages 132–140 Maguire, L. A. 2004. What can decision anal- in Turning the tide: The eradication of ysis do for invasive species management? invasive species. Proceedings of the inter- Risk Anal. 24:859–868. national conference on eradication of is- Margiasso, M. E., K. M. Longpre, and L. S. land invasives. Occasional Paper of the Katz. 2010. Partner preference: Assessing IUCN Species Survival Commission. the role of the female goat. Physiol. Behav. ———. 2011. Invasive species removal and 99:587–591. ecosystem recovery in the Mariana Islands: McCammon-Feldman, B. 1980. A critical Challenges and outcomes on Sarigan and analysis of tropical savanna forage con- Anatahan. Pages 320 –324 in C. R. Veitch, sumption and utilization by goats. Ph.D. M. N. Clout, and D. R. Towns, eds. Island diss., University of Illinois, Urbana. invasives: Eradication and management. Merlin, M. D., and J. O. Juvik. 1992. Rela- IUCN, Gland, Switzerland. tionships among native and alien plants King, D. 1992. Home ranges of feral goats in on Pacific islands with and without signifi- a pastoral area in Western Australia. Wildl. cant human disturbance and feral ungu- Res. 19:643– 649. lates. Pages 597– 624 in C. Stone, C. Smith, King, W. B. 1985. Island birds: Will the fu- and J. Tunison, eds. Alien plant invasions ture repeat the past? Pages 3–15 in P. J. in native ecosystems of Hawai‘i. Coopera- Moors, ed. Conservation of island birds: tive National Parks Resources Studies Case studies for the management of threat- Unit, University of Hawai‘i at Mänoa, ened island species. International Council Honolulu. for Bird Preservation Technical Publica- Morris, D. K. 1969. Summer food habits of tion 3. feral goats in Hawaii Volcanoes National Kirton, A. 1977. Live weights of farmed feral Park. Unpubl. NPS Rep. 17 p. goats Capra hircus. N. Z. J. Exp. Agric. 5:7– North, R. 2004. Anatomy and physiology of 10. the goat. New South Wales Department of Kjargaard, J. 1984. Some aspects of feral goat Primary Industries Agfact A7.0.3. 2nd ed. distribution in Haleakala National Park. Nowak, R. M., and J. L. Paradiso. 1983. Cooperative National Parks Resources Walker’s mammals of the world. 4th ed. Studies Unit, University of Hawai‘i at Johns Hopkins University, Baltimore, Mänoa, Honolulu. Maryland. Pacific Island Invasive Species: Capra hircus, the Feral Goat · Chynoweth et al. 155

O’Brien, P. H. 1982. Flehmen: Its occurrence Rainbolt, R. E., and B. E. Coblentz. 1999. and possible functions in feral goats. Anim. Restoration of insular ecosystems: Control Behav. 30:1015–1019. of feral goats on Aldabra Atoll, Republic of ———. 1983. Feral goat parturition and Seychelles. Biol. Invasions 1:363–375. lying-out sites: Spatial, physical and mete- Ramsay, B. J. 1994. Commercial use of wild orological characteristics. Appl. Anim. animals in Australia. Bureau of Resource Ethol. 10:325–339. Sciences, Canberra. ———. 1984a. Feral goat home range: Influ- Robbins, C. T. 1994. Wildlife feeding and ence of social class and environmental vari- nutrition. 2nd ed. Elsevier Science, Or- ables. Appl. Anim. Behav. Sci. 12:373–385. lando, Florida. ———. 1984b. Leavers and stayers: Maternal Rudge, M. R. 1969. Reproduction of feral post-partum strategies in feral goats. Appl. goats Capra hircus L. near Wellington, Anim. Behav. Sci. 12:233–243. New Zealand. N. Z. J. Sci. 12:817–827. ———. 1988. Feral goat social organization: Rudge, M. R., and T. J. Smith. 1970. Ex- A review and comparative analysis. Appl. pected rate of increase of hunted popula- Anim. Behav. Sci. 21:209–221. tions of feral goats (Capra hircus L.) in New Odour, A. M. O., J. M. Gómez, and S. Y. Zealand. N. Z. J. Sci. 13:256 –259. Strauss. 2010. Exotic vertebrate and in- Ruiz-Miranda, C. R., M. D. Szymanski, and vertebrate herbivores differ in their im- J. W. Ingals. 1993. Physical characteristics pacts on native and exotic plants: A meta- of the vocalizations of domestic goat does analysis. Biol. Invasions 12:407– 419. Capra hircus in response to their offspring’s Ohashi, T. J., and S. D. Schemnitz. 1987. cries. Bioacoustics 5:99–116. Birth pattern of feral goats on Haleakala. Sakanoue, S., N. Kitahara, and H. Hayashi. ‘Elepaio 47:99–102. 1995. Biological control of Rumex obtusifo- Ostertag, R., S. Cordell, J. Michaud, T. C. lius L. by goat grazing. Jpn. Agric. Res. Q. Cole, J. R. Schulten, K. M. Publico, and 29:39– 42. J. H. Enoka. 2009. Ecosystem and restora- Saunders, F. C., A. G. McElligott, K. Safi, tion consequences of invasive woody spe- and T. J. Hayden. 2005. Mating tactics of cies removal in Hawaiian lowland wet for- male feral goats (Capra hircus): Risks and est. Ecosystems 12:503–515. benefits. Acta Ethol. 8:103–110. Parker, J. D., D. E. Burkepile, and M. E. Hay. Scowcroft, P. G., and R. Hobdy. 1987. Re- 2006. Opposing effects of native and exotic covery of goat-damaged vegetation in an herbivores on plant invasions. Science insular tropical montane forest. Biotropica ( Washington, D.C.) 311:459– 461. 19:208–215. Parkes, J. P. 1984. Feral goats on Raoul Is- Scowcroft, P. G., and H. F. Sakai. 1983. Im- land: Effect of control methods on their pact of feral herbivores on mämane forests density, distribution, and productivity. of Mauna Kea, Hawai‘i: Bark stripping and N. Z. J. Ecol. 7:85–94. diameter class structure. J. Range Manage. ———. 1990. Feral goat control in New Zea- 36:495– 498. land. Biol. Conserv. 54:335–348. Shackleton, D. M., and C. C. Shank. 1984. Parkes, J., R. Henzell, and G. Pickles. 1996. A review of the social behavior of feral Managing vertebrate pests: Feral goats. and wild sheep and goats. J. Anim. Sci. Australian Government Publishing Ser- 58:500 –509. vice, Canberra. Sheley, R. L., and J. K. Petroff. 1999. Biology Phillips, R. W., V. L. Simmons, and R. G. and management of noxious rangeland Schott. 1943. Observations on the hor- weeds. Oregon State University Press, monal estrous cycle and breeding season Corvallis. in goats and possibilities of modification of Smith, M. C., and D. M. Sherman. 1994. the breeding season with gonadotropic Goat medicine. Blackwell Publishing Asia, hormones. Am. J. Vet. Res. 4:360 –367. Carlton, Victoria, Australia. 156 PACIFIC SCIENCE · April 2013

Spatz, G., and D. Mueller-Dombois. 1973. Tracey, J. P., and P. J. S. Fleming. 2007. Be- The inﬂuence of feral goats on koa tree re- havioural responses of feral goats (Capra production in Hawai‘i Volcanoes National hircus) to helicopters. Appl. Anim. Behav. Park. Ecology 54:870 –876. Sci. 108:114 –128. Stephens, R. M., S. C. Hess, and B. Kawaka- Turner, C. W. 1936. Seasonal variation in the mi Jr. 2008. Controlling mouﬂon sheep at birth rate of the milking goat in the United the Kahuku Unit of Hawai‘i Volcanoes States. J. Dairy Sci. 19:619– 622. National Park. Proc. Vertebr. Pest Conf. Veitch, C. R., and M. N. Clout. 2002. Turn- 23: 304 –309. ing the tide: The eradication of invasive Stone, C. P. 1985. Alien animals in Hawai‘i’s species. IUCN Species Specialist Group, native ecosystems: Toward controlling the Gland, Switzerland, and Cambridge, adverse effects of introduced vertebrates. United Kingdom. Pages 251–297 in C. P. Stone and J. M. Veltman, C. J., and J. Parkes. 2002. The Scott, eds. Hawai‘i’s terrestrial ecosystems: potential of poisoned foliage as bait for Preservation and management. University controlling feral goats (Capra hircus). Sci. of Hawai‘i Press, Honolulu. Conserv. 204:1–21. Stone, C. P., L. W. Cuddihy, and J. T. Tuni- Watts, T., and W. Conley. 1984. Reproduc- son. 1992. Responses of Hawaiian ecosys- tive potential and theoretical rates of in- tems to removal of feral pigs and goats. crease for feral goat populations. J. Wildl. Pages 666 –704 in C. P. Stone, C. W. Manage. 48:814 –822. Smith, and J. T. Tunison, eds. Alien plant Wester, L. 1991. Invasions and extinctions on invasions in native ecosystems of Hawai‘i. Masatierra ( Juan Fernandez Islands): A re- Cooperative National Parks Resources view of early historical evidence. J. Hist. Studies Unit, University of Hawai‘i at Geogr. 17:18–34. Mänoa, Honolulu. Wilcove, D. S., D. Rothstein, J. Dubow, A. Taylor, D., and L. Katahira. 1988. Radio te- Phillips, and E. Losos. 1998. Quantifying lemetry as an aid in eradicating remnant threats to imperiled species in the United feral goats. Wildl. Soc. Bull. 16:297–299. States. BioScience 48:607– 615. Thaxton, J. M., T. C. Cole, S. Cordell, R. J. Yocom, C. F. 1967. Ecology of feral goats in Cabin, D. R. Sandquist, and C. M. Litton. Haleakala National Park, Maui, Hawai‘i. 2010. Native species regeneration follow- Am. Midl. Nat. 77:418– 451. ing ungulate exclusion and nonnative grass Zeder, M. A., and B. Hesse. 2000. The initial removal in a remnant Hawaiian dry forest. domestication of goats (Capra hircus) in Pac. Sci. 64:533–544. the Zagros Mountains 10,000 years ago. Thompson, J., J. Riethmuller, D. Kelly, E. Science ( Washington, D.C.) 287:2254 – Miller, and J. C. Scanlan. 2002. Feral goats 2257. in south-western Queensland: A perma- Zhang, H., Y. Wang, and Z. Zhang. 2009. nent component of the grazing lands. Domestic goat grazing disturbance en- Rangeland J. 24:268–287. hances tree seed removal and caching by Thornes, J. 1985. The ecology of erosion. small rodents in a warm-temperate de- Geography 70:222–235. ciduous forest in China. Wildl. Res. Tomich, P. Q. 1986. Mammals in Hawai‘i: A 36:610 – 616. synopsis and notational bibliography. 2nd ed. Bishop Museum Press, Honolulu.