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As the ?rst step towards the ecological restoration of its islands, Mexico has completed 60 eradications of invasive mammals thanks to a strong partnership between Grupo de Ecología y Conservación de Islas, A.C. (GECI), the federal government, local ?shing communities, academia, and private donors. The removal of invasive mammals has led to the dramatic recovery of the islands’ ecosystems. On Guadalupe Island, after completing the goat eradication in 2007, the native vegetation started to recover. Plants considered extinct or extirpated have been rediscovered, and plant species new to the island have been recorded. However, in order to achieve the island’s full recovery, the active restoration of degraded soils and vegetation are needed. To date, GECI, in collaboration with the National Forestry Commission (CONAFOR) and the National Commission for Natural Protected Areas (CONANP), is implementing a 700 ha project to accelerate the restoration of the native vegetation communities. The project involves reforestation, erosion control, and ? re prevention actions on different plant communities: forests and sage scrub. An on-site nursery has been established, seedlings—mostly from endemic trees—are being grown, and on-site reforestation planting has started. Up to June 2018, we have planted almost 40,000 trees, and will produce 160,000 seedlings during this year. Mechanical methods to control and prevent erosion have been used as we have installed more than 2,400 m of contour barriers, 57 m3 of dams, and rehabilitated ?rebreaks. The actions will continue: the long-term goal being the comprehensive restoration of the vegetation communities devastated by feral goats. The Guadalupe Island experience will be useful to inform the restoration of other Mexican islands.

The Baja California Pacifc Islands, Mexico, are globally important breeding sites for 22 seabird species and subspecies. In the past, several populations were extirpated or reduced due to invasive mammals, human disturbance, and contaminants. Over the past two decades, we have removed invasive predators and, for the last decade, we have been implementing a Seabird Restoration Programme on eight groups of islands: Coronado, Todos Santos, San Martín, San Jerónimo, San Benito, Natividad, San Roque, and Asunción. This programme includes monitoring; social attraction techniques; removal of invasive vegetation; reducing human disturbance; and an environmental learning and biosecurity programme. Here, we summarise historical extirpations and recolonisations during the last two decades of restoration actions, and we update the status of breeding species after more than a decade. To date, from 27 historically extirpated populations, 80% have returned since the ?rst eradication in 1995. Social attraction techniques were key in recolonisations of Cassin’s auklet (Ptychoramphus aleuticus), royal tern (Thalasseus maximus), and elegant tern (T. elegans). A total of 19 species breed on these islands, four more species than a decade ago, including 12 new records. The most abundant seabirds, black-vented shearwater (Puffnus opisthomelas), Cassin’s auklet, western gull (Larus occidentalis), and Brandt’s cormorant (Phalacrocorax penicillatus), have shown a remarkable population increase. Current threats include the potential reintroduction of invasive mammals, guano mining, recreational activities, pollution, and commercial ?sheries. To maintain these conservation gains in the long-term it is necessary to continue implementing restoration actions and reinforcing protection on these important natural protected areas.

Socorro Island is part of the Revillagigedo National Park, Mexico. At 132 km2, it is the Mexican island with the highest level of endemism. It provides habitat for 117 vascular plant species, 26% of which are endemic. There is also an endemic blue lizard (Urosaurus auriculatus) and eight endemic terrestrial birds. Socorro’s ecosystem had been heavily degraded by invasive mammals for the past 140 years. Feral sheep (Ovis aries) destroyed one third of the island’s habitat and feral cats (Felis catus) severely impacted the island’s avifauna and the Socorro blue lizard. Together, feral sheep and cats are responsible for the extinction in the wild of the Socorro dove (Zenaida graysoni) and the Socorro elf owl (Micrathene whitneyi graysoni) and have been a serious threat to other vulnerable species, particularly Townsend’s shearwater (Pu?nus auricularis). As such, the island’s restoration is a high priority. We conducted a feral sheep eradication from 2009 to 2012, using aerial and terrestrial methods, aided by Judas sheep and trained dogs, to kill 1,762 animals. The vegetation recovery has been remarkable, as well as the improvement of soil properties such as compaction, nitrogen, organic carbon, phosphorus, and calcium. In 2011, we initiated a feral cat control programme, which soon became an eradication project. The ongoing feral cat eradication has been a challenge, due to Socorro’s large size, vegetation and topographical complexity. By December 2016, 502 cats had been dispatched, using soft leg-hold traps equipped with telemetry transmitters and lethal traps: a total e? ort of 50,000 trap-nights. Cat abundance has decreased very signi?cantly and catch per unit of e? ort indicates that the eradication is nearing completion. The abundance of the Socorro blue lizard and terrestrial birds has already increased. We estimate completing the feral cat eradication by the end of 2017, when we will shift to a veri?cation of eradication phase.

A non-native introduced population of rhesus macaques (Macaca mulatta) was targeted for removal from Desecheo Island (117 ha), Puerto Rico. Macaques were introduced in 1966 and contributed to several plant and animal extirpations. Since their release, three eradication campaigns were unsuccessful at removing the population; a fourth campaign that addressed potential causes for previous failures was declared successful in 2017. Key attributes that led to the success of this campaign included a robust partnership, adequate funding, and skilled ?eld sta? with a strong eradication ethic that followed a plan based on eradication theory. Furthermore, the incorporation of modern technology including strategic use of remote camera traps, monitoring of radio-collared Judas animals, night hunting with night vision and thermal ri?e scopes, and the use of high-power semi-automatic ? rearms made eradication feasible due to an increase in the probability of detection and likelihood of removal. Precision shooting and trapping were the primary methods used throughout the campaign. Long-term monitoring using camera traps and observed sign guided a management strategy that adapted over time in response to population density and structure. Lessons learnt include, 1) macaques quickly adjusted their behaviour in response to human presence and removal methods, 2) camera traps and thermal scopes provided high detection likelihood compared to other methods, and 3) the use of Judas animals and night hunting with thermal and night vision ri?e-scopes facilitated removals. The removal of macaques from Desecheo Island appears to be the ?rst introduced non-hominid primate eradication from an island.

Invasive rodents are present on approximately 80% of the world’s islands and constitute one of the most serious threats to island biodiversity and ecosystem functioning. The eradication of rodents is central to island conservation eff orts and the aerial broadcast of rodenticide bait is the preferred dispersal method. To improve the efficiency of rodent eradication campaigns, the generation of accurate and real-time bait density maps is required. Creating maps to estimate the spatial dispersion of bait on the ground has been carried out using traditional GIS methodologies, which are based on limiting assumptions and are time intensive. To improve accuracy and expedite the evaluation of aerial operations, we developed an algorithm for the numerical estimation of rodenticide density (NERD). The NERD algorithm performs calculations with increased accuracy, displaying results almost in real-time. NERD describes the relationship between bait density, the mass fl ow rate of rodenticide through the bait bucket, and helicopter speed and produces maps of bait density on the ground. NERD also facilitates the planning of helicopter fl ight paths and allows for the instant identification of areas with low or high bait density. During the recent and successful rodent eradication campaign on Banco Chinchorro in Mexico, carried out during 2015, NERD results were used to enable dynamic decision-making in the fi eld and to ensure the efficient use of resources.

Invasive black rats (Rattus rattus) were successfully eradicated during 2012 from Pinzon Island in the Galapagos archipelago using the rodenticide brodifacoum. Potential exposure to brodifacoum in Pinzon tortoises (Chelonoidis ephippium), Pinzon lava lizards (Microlophus duncanensis) and Galapagos hawks (Buteo galapagoensis) was mitigated by captive holding of subpopulations. This was successful for all species during and shortly after baiting, however mortality of Galapagos hawks occurred post-release, likely due to the persistence of residual brodifacoum in lava lizards. Since 2013, Pinzon tortoise hatchlings are surviving in-situ for the fi rst time in at least 120 years and the eradication of black rats is expected to have significant benefits for at least 15 other island-endemic species.

Invasive rodents have significant negative impacts on island biodiversity. All but the smallest of rodent eradications currently rely on island-wide rodenticide applications. Although significant advances have been made in mitigating unintended impacts, rodent eradication on inhabited islands remains extremely challenging. Current tools restrict eradication efforts to fewer than 15% of islands with critically endangered or endangered species threatened by invasive rodents. The Genetic Biocontrol of Invasive Rodents partnership is an interdisciplinary collaboration to develop and evaluate gene drive technology for eradicating invasive rodent populations on islands. Technological approaches currently being investigated include the production of multiple strains of Mus musculus with a modified form of the native t-complex, or a CRISPR gene drive, carrying genes or mechanisms that determine sex. These systems have the potential to skew the sex ratio of off spring to approach 100% single-sex, which could result in population collapse. One goal proposed is to test the ability of constructs to spread and increase in frequency in M. musculus populations in biosecure, captive settings and undertake modelling to inform development and potential deployment of these systems. Structured ecologically-based risk assessments are proposed, along with social and cultural engagement to assess the acceptability of releasing a gene drive system. Work will be guided by an external ethics advisory board. Partners are from three countries with significant regulatory capacity (USA, Australia, New Zealand). Thus, we will seek data sharing agreements so that results from experiments may be used within all three countries and treat regulatory requirements as a minimum. Species-specific, scalable, and socially acceptable new eradication tools could produce substantial biodiversity benefits not possible with current technologies. Gene drive innovation may provide such a tool for invasive species management and be potentially transformative and worthy of exploring in an inclusive, responsible, and ethical manner.

Eradication of invasive rodents has become a powerful tool to protect native island biota. Use of brodifacoum, an anticoagulant rodenticide, has contributed to hundreds of successful invasive rodent eradication e?orts on islands. Application of bait containing brodifacoum for this purpose requires appropriate consideration of adverse e?ects on non-target wildlife. Thus, a priori identi?cation of non-target risks and, where needed, approaches to mitigate these to acceptable levels, is now an essential component of eradication planning and implementation. As part of the plan for eradicating invasive rats and mice from Floreana Island in the Galapagos, we experimentally tested the e?ect of brodifacoum on the Galapagos endemic land snail species Naesiotus unifasciatus. Importantly, the trials were designed to evaluate e?ects of particular components of the bait pellets, namely the active brodifacoum, the pyranine biomarker, and a blue dye. We found no evidence for increased snail mortality following exposure to any of these bait components. We review results of past toxicity studies on terrestrial molluscs and ?nd that, as for our own study, there is likely to be little impact of anticoagulant rodenticide on terrestrial mollusc survival as the result of application of brodifacoum bait. However, given the limited taxonomic representation in the toxicity tests performed on terrestrial molluscs so far, we recommend the continued used of captive toxicity trials to assess potential e?ect of any rodenticide applications on native malacological fauna on a case-by-case basis where large-scale eradication programmes are planned and undertaken.