[Show abstract][Hide abstract] ABSTRACT: Invasive alien mammals are the major driver of biodiversity loss and ecosystem degradation on islands. Over the past three decades, invasive mammal eradication from islands has become one of society's most powerful tools for preventing extinction of insular endemics and restoring insular ecosystems. As practitioners tackle larger islands for restoration, three factors will heavily influence success and outcomes: the degree of local support, the ability to mitigate for non-target impacts, and the ability to eradicate non-native species more cost-effectively. Investments in removing invasive species, however, must be weighed against the risk of reintroduction. One way to reduce reintroduction risks is to eradicate the target invasive species from an entire archipelago, and thus eliminate readily available sources. We illustrate the costs and benefits of this approach with the efforts to remove invasive goats from the Galápagos Islands. Project Isabela, the world's largest island restoration effort to date, removed >140,000 goats from >500,000 ha for a cost of US$10.5 million. Leveraging the capacity built during Project Isabela, and given that goat reintroductions have been common over the past decade, we implemented an archipelago-wide goat eradication strategy. Feral goats remain on three islands in the archipelago, and removal efforts are underway. Efforts on the Galápagos Islands demonstrate that for some species, island size is no longer the limiting factor with respect to eradication. Rather, bureaucratic processes, financing, political will, and stakeholder approval appear to be the new challenges. Eradication efforts have delivered a suite of biodiversity benefits that are in the process of revealing themselves. The costs of rectifying intentional reintroductions are high in terms of financial and human resources. Reducing the archipelago-wide goat density to low levels is a technical approach to reducing reintroduction risk in the short-term, and is being complemented with a longer-term social approach focused on education and governance.
PLoS ONE 05/2011; 6(5):e18835. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A three-year programme to eradicate Feral Cats Felis catus from the island of Baltra in the Galapagos archipelago achieved good results by Initially poisoning with sodium monofluoroacetate (compound 1080) then trapping or shooting the remaining cats. The poisoning campaign removed 90% of the cats, its success being attributable to pre-baiting with unpolsoned baits to accustom cats to eating baits and placing enough baits to ensure that all cats encountered several baits within their home range. This, together with the use of metaclopromide (Pileran) as an anti-emetic, overcame a problem associated with poor retention of 1080 in thawed fish baits that limited the dose available to 1 mg 1080lbait, a quality Insufficient to kill large cats. Removal of the remaining cats was delayed by a weather-Induced irruption of Black Rats Rattus rattus and House Mice Mus musculus that enabled recruitment of kittens in 2002, but made cats more susceptible to trapping and shooting in 2003 when rodent populations collapsed. Since July 2003 no sign of a cat has been detected on Baltra despite extensive searching and monitoring throughout 2004. As cat abundance has decreased there have been more locally-bred Juvenile iguanas (Conolophus subcristatus) seen during annual censuses. However, such recruitment may reflect the increasing maturity and higher fecundity of iguanas repatriated from 1991 onwards rather than being a direct result of reduced cat predation alone. More time is necessary to determine the benefits of reduced cat predation on the Iguana population.
[Show abstract][Hide abstract] ABSTRACT: Starting in the late 1970s, ecologists began unraveling the role of recently extinct large vertebrates in evolutionary ecology and ecosystem dynamics. Three decades later, practitioners are now considering the role of ecological history in conservation practice, and some have called for restoring missing ecological functions and evolutionary potential using taxon substitutes - extant, functionally similar taxa - to replace extinct species. This pro-active approach to biodiversity conservation has proved controversial. Yet, rewilding with taxon substitutes, or ecological analogues, is now being integrated into conservation and restoration programmes around the world. Empirical evidence is emerging that illustrates how taxon substitutions can restore missing ecological functions and evolutionary potential. However, a major roadblock to a broader evaluation and application of taxon substitution is the lack of practical guidelines within which they should be conducted. While the International Union for Conservation of Nature's reintroduction guidelines are an obvious choice, they are unsuitable in their current form. We recommend necessary amendments to these guidelines to explicitly address taxon substitutions. A second impediment to empirical evaluations of rewilding with taxon substitutions is the sheer scale of some proposed projects; the majority involves large mammals over large areas. We present and discuss evidence that large and giant tortoises (family Testudinidae) are a useful model to rapidly provide empirical assessments of the use of taxon substitutes on a comparatively smaller scale. Worldwide, at least 36 species of large and giant tortoises went extinct since the late Pleistocene, leaving 32 extant species. We examine the latent conservation potential, benefits, and risks of using tortoise taxon substitutes as a strategy for restoring dysfunctional ecosystems. We highlight how, especially on islands, conservation practitioners are starting to employ extant large tortoises in ecosystems to replace extinct tortoises that once played keystone roles. 2010 The Authors. Journal compilation 2010 Ecography.
[Show abstract][Hide abstract] ABSTRACT: Invasive mammals are premier drivers of extinction and ecosystem change, particularly on islands. In the 1960s, conservation practitioners started developing techniques to eradicate invasive mammal populations from islands. Larger and more biologically complex islands are being targeted for restoration worldwide. We conducted a feral goat (Capra hircus) eradication campaign on Santiago Island in the Galápagos archipelago, which was an unprecedented advance in the ability to reverse biodiversity impacts by invasive species. We removed >79,000 goats from Santiago Island (58,465 ha) in <4.5 years, at an approximate cost of US$6.1 million. An eradication ethic combined with a suite of techniques and technologies made eradication possible. A field-based Geographic Information System facilitated an adaptive management strategy, including adjustment and integration of hunting methods. Specialized ground hunting techniques with dogs removed most of the goat population. Aerial hunting by helicopter and Judas goat techniques were also critical. Mata Hari goats, sterilized female Judas goats induced into a long-term estrus, removed males from the remnant feral population at an elevated rate, which likely decreased the length and cost of the eradication campaign. The last 1,000 goats cost US$2.0 million to remove; we spent an additional US$467,064 on monitoring to confirm eradication. Aerial hunting is cost-effective even in countries where labor is inexpensive. Local sociopolitical environments and best practices emerging from large-scale, fast-paced eradications should drive future strategies. For nonnative ungulate eradications, island size is arguably no longer the limiting factor. Future challenges will involve removing invasive mammals from large inhabited islands while increasing cost-effectiveness of removing low-density populations and confirming eradication. Those challenges will require leveraging technology and applying theory from other disciplines, along with conservation practitioners working alongside sociologists and educators.
Journal of Wildlife Management 02/2009; · 1.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Rails (family Rallidae) are vulnerable to the impacts of invasive mammals, and this is particularly true for species on oceanic islands. The endemic Galápagos rail (Laterallus spilonotus) is no exception; previous studies suggested that Galápagos rail populations were heavily impacted due to predation by pigs (Sus scrofa) and habitat degradation by goats (Capra hircus). Following recent conservation actions that have eradicated pigs and goats from Santiago Island, changes in rail abundance were observed. Estimated densities have increased by over an order of magnitude between 1986/1987 and 2004/2005. Limited data on rail densities from two additional islands over the same time period provide further support to the notion that the eradications spurred recovery. On Fernandina Island, where there is no history of invasive mammals, rail density increased slightly between 1986/1987 and 2004/2005. In contrast, on Isabela Island where invasive mammals were present both in 1986/1987 and 2004/2005, rail densities declined at one site between those two time periods. While the Galápagos rail is vulnerable to invasive mammals, the observed changes following goat and pig removal are encouraging for Rallidae conservation.
[Show abstract][Hide abstract] ABSTRACT: Introduced herbivores are major drivers of ecosystem change and biodiversity loss, particularly on islands. Tools and techniques
now exist to routinely remove introduced herbivores from islands, providing a powerful conservation tool. Here, we summarize
the few documented feral donkey removals on islands worldwide, and report on the removal of populations from the Galápagos
archipelago, Ecuador. After decades of sporadic control programs on Santiago Island and Alcedo Volcano, Isabela Island, donkey
populations were removed from both areas, concurrent with a goat eradication program. Both ground and aerial hunting programs
were utilized. The latter method was highly efficient; donkeys were removed from Santiago Island with less than 80 h of aerial
hunting. Given the clear impacts of introduced herbivores on islands worldwide, feral donkey populations should be routinely
removed from islands.
Biodiversity and Conservation 04/2007; 16(2):437-445. · 2.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Non-native mammals are major drivers of ecosystem change and biodiversity loss; this is especially apparent on islands. However,
techniques exist to remove non-native mammals, providing a powerful conservation tool. Conservation practitioners are now
targeting larger islands for restoration. Leveraging existing and developing new techniques and technologies will prove critical
to successful eradications on large islands. Using the removal of introduced goats (Caprahircus) from Santiago Island, Galápagos as a case study, we present a suite of Geographic Information System (GIS) tools that aid
island conservation actions. GIS tools were incorporated into the three phases of the eradication campaign: planning, hunting,
and monitoring. Further, these tools were adopted for three eradication techniques: ground-based hunting, aerial hunting by
helicopter, and Judas goats. These geographic approaches provide a foundation for statistical, spatial, and economic analyses
that should increase the capability and efficiency of removal campaigns. Given limited conservation funds and the dire status
of many insular species, efficiently removing non-native mammals from islands is of paramount global conservation importance.
[Show abstract][Hide abstract] ABSTRACT: The use of Judas goats (JGs; Capra hircus) to locate remnant animals is a powerful tool for enhancing feral goat eradication efforts, being especially important to island conservation programs. JGs are goats that are captured, fitted with radio telemetry collars and released. As goats are gregarious, JGs search out and associate with other goats. They can then be tracked down and any associated feral goats removed. JGs increase the efficiency of removing animals at low densities by reducing search time for hunters locating remnant herds. Prolonged duration or increased frequency of estrus in female JGs could potentially increase the efficiency of this method; does in estrus actively seek out and are searched for by bucks, and are more active than non-estrus does. Two experiments under controlled, farm conditions demonstrated that estrus can be prolonged by using Compudose-100 implants (one or two implants; single dose 21.1 mg estradiol 17β) or a single Synovex-S implant (200 mg progesterone and 20 mg estradiol benzoate). Two Synovex-S implants failed to significantly prolong estrus. Single Compudose-100 implants provided the most dramatic effect, and when combined with 15 mg PGF2∝ and sterilization by tubal occlusion provides an effective means of terminating pregnancy, inducing sterility and prolonging estrus 6–16-fold compared to sterile does and at least 82-fold compared to unaltered does, with a single intervention. Incorporating these methods into Judas goat programs will likely increase the efficiency and capability of feral goat control and island conservation.
[Show abstract][Hide abstract] ABSTRACT: Introduced mammals are major drivers of extinction. Feral goats (Capra hircus) are particularly devastating to island ecosystems, causing direct and indirect impacts through overgrazing, which often results in ecosystem degradation and biodiversity loss. Removing goat populations from islands is a powerful conservation tool to prevent extinctions and restore ecosystems. Goats have been eradicated successfully from 120 islands worldwide. With newly developed technology and techniques, island size is perhaps no longer a limiting factor in the successful removal of introduced goat populations. Furthermore, the use of global positioning systems, geographic information systems, aerial hunting by helicopter, specialized hunting dogs, and Judas goats has dramatically increased efficiency and significantly reduced the duration of eradication campaigns. Intensive monitoring programs are also critical for successful eradications. Because of the presence of humans with domestic goat populations on large islands, future island conservation actions will require eradication programs that involve local island inhabitants in a collaborative approach with biologists, sociologists, and educators. Given the clear biodiversity benefits, introduced goat populations should be routinely removed from islands.Resumen: Los mamíferos introducidos son los principales causantes de extinción. Las cabras ferales (Capra hircus) son particularmente devastadoras de ecosistemas insulares, provocando impactos directos e indirectos por sobrepastoreo, que a menudo resulta en la degradación del ecosistema y la pérdida de biodiversidad. La remoción de poblaciones de cabras de las islas es una poderosa herramienta de conservación para prevenir de extinciones y restaurar ecosistemas. Se han erradicado cabras exitosamente de 120 islas a nivel mundial. Con tecnología y técnicas desarrolladas recientemente, el tamaño de la isla ya no es un factor limitante en la remoción exitosa de poblaciones introducidas de cabras. Más aun, el uso de sistemas de posicionamiento global, sistemas de información geográfica, cacería aérea desde helicóptero, perros de caza especializados y cabras Judas han incrementado la eficiencia dramáticamente y reducido la duración de las campañas de erradicación significativamente. Los programas de monitoreo intensivo también son críticos para las erradicaciones exitosas. Debido a la presencia de humanos con poblaciones de cabras domésticas en las islas grandes, las acciones de conservación en el futuro requerirán de programas de erradicación que involucren a los habitantes locales en un esfuerzo cooperativo con biólogos, sociólogos y educadores. Dados los claros beneficios para la biodiversidad, las poblaciones de cabras introducidas deberán ser removidas de las islas rutinariamente.
[Show abstract][Hide abstract] ABSTRACT: Introduced mammals are major drivers of extinction and ecosystem change. As omnivores, feral pigs (Sus scrofa) are responsible for wholesale adverse effects on islands. Here, we report on the eradication of feral pigs from Santiago Island in the Galápagos Archipelago, Ecuador, which is the largest insular pig removal to date. Using a combination of ground hunting and poisoning, over 18,000 pigs were removed during this 30-year eradication campaign. A sustained effort, an effective poisoning campaign concurrent with the hunting program, access to animals by cutting more trails, and an intensive monitoring program all proved critical to the successful eradication. While low and fluctuating control efforts may help protect select native species, current eradication methods, limited conservation funds, and the potential negative non-target impacts of sustained control efforts all favor an intense eradication effort, rather than a sustained control program. The successful removal of pigs from Santiago Island sets a new precedent, nearly doubling the current size of a successful eradication, and is leading to more ambitious projects. However, now we must turn toward increasing eradication efficiency. Given limited conservation funds, we can no longer afford to spend decades removing introduced mammals from islands.
[Show abstract][Hide abstract] ABSTRACT: The use of Judas goats to locate remnant animals is a potentially powerful tool for enhancing goat-eradication efforts, which are especially important to island conservation. However, current Judas goat methodology falls short of its potential efficacy. Female Judas goats are often pregnant at the time of deployment or become impregnated in the field; pregnant females leave associated goats to give birth, causing downtime of Judas goat operations. Further, male Judas goats may inseminate remnant females. Sterilising Judas goats prior to deployment removes these inefficiencies. Here, we describe two methods (epididymectomy for males and tubal occlusion for females) that sterilise Judas goats while still maintaining sexual motivation and other behaviours associated with intact animals. These surgeries are straightforward, time efficient, and may be conducted in the field by staff with minimal training. Given the widespread and deleterious impacts of non-native herbivores to ecosystems and the importance of Judas operations in detecting animals at low densities, sterilisation and termination of pregnancy should be applied routinely in Judas goat (and possibly other species) programs to increase the efficacy of low-density control operations and eradication campaigns.
CSIRO Wildlife Research 01/2005; · 1.19 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Over the last 30 years techniques have been developed to eradicate feral goat populations from islands (Daly, 1989; Veitch & Clout, 2002). These techniques, which include both ground and aerial hunting campaigns, as well as the use of Judas goats, have resulted in the successful eradication of goats from >100 islands world-wide (K. Campbell, unpub. data). The use of Judas goats, radio-collared individuals that are released and associate with conspecifics, aid in removing goats at low densities (Taylor & Katahira, 1988; Rainbolt & Coblentz, 1999). Unfortunately, the majority of eradication efforts remain unpublished, and as a result such knowledge is often unavailable to conservation practitioners (Simberloff, 2001; Donlan et al., 2003). Here, we report on the 30-year eradication campaign of goats from Pinta Island in the Galápagos Archipelago, Ecuador, the largest insular goat population removal using ground-based methods to date. Over 41,000 goats were removed from Pinta during an initial hunting campaign. In the decade following, the island was twice wrongly declared eradicated (Calvopiña, 1985; Evans, 1990), highlighting the need for regular monitoring programmes. Revised hunting techniques and a monitor-ing programme were implemented in 1999. With this programme in place, the island is now free of goats. Pinta Island (5,940 ha), located in the northern part of the Galápagos archipelago, enjoys protected status and receives little visitation by scientists or managers and Abstract Introduced mammals are a major driver of extinction and ecosystem change, particularly on islands. Feral goats Capra hircus have been introduced to numer-ous islands worldwide and have had wholesale impacts on ecosystems. Techniques are now available, however, to eradicate goat populations from islands, providing a powerful conservation tool. Goats were removed from Pinta Island, Galápagos, Ecuador after a 30-year eradi-cation campaign, the largest removal of an insular goat population using ground-based methods. Over 41,000 goats were removed during the initial hunting effort (1971–82). In the following decade the island was twice wrongly declared free of goats. During this period, the island was visited irregularly but no monitoring programme was implemented. A revised campaign over 1999–2003, which included improved hunting tech-niques and monitoring, removed the final goats from the island. The use of Judas goats was critical in locating the remaining goats and as a tool to confirm eradication. A systematic monitoring programme is critical for confirm-ing eradication and preventing future reintroductions. An earlier monitoring programme would probably have resulted in earlier eradication and significant financial savings. Given limited resources, island conser-vation programmes elsewhere should strive to increase eradication efficiency and learn from past campaigns.
[Show abstract][Hide abstract] ABSTRACT: We believe that an explicit collaboration between conservation researchers and conservation practitioners is needed that (1) quantifies and publicizes the efficacy of eradication of invasive species from islands (e.g., Veitch & Clout 2002), (2) critically evaluates existing tools for invasive-species eradication (e.g., Nogales et al., 2004), (3) develops new eradication tools (e.g., Courchamp & Cornell 2000), and (4) exploits eradication programs as large-scale ecological experiments (e.g., Donlan et al. 2002).