Eradication of invasive mammals on islands inhabited by humans and domestic animals

For birds and humans: challenges and benefits of rat eradication from an inhabited island (Ventotene, central Italy)

BACKGROUND

Rat eradication from islands is a very effective tool that can free entire ecosystems from the pressure of alien predators. In this study we present the case study of Ventotene (Ponziane Archipelago, central Italy), which to date is the island with by far the greatest number of human inhabitants ever freed from the negative implications of rats. Rat eradication was carried out in the framework of the Life PonDerat project, co-financed by the European Union. Besides considering the conservation benefits due to the removal of rats, we also considered the socio-economic and pathogenic impacts from introduced rats.

RESULTS

The overall economic cost of the rats was quantified to be at least €18 500 per year to the residents of the island. Several zoonotic pathogens were detected in the rat population prior to eradication. A reduction in the rodenticide distributed over time on the island was also estimated. Identifying the origin of the rat population allowed for the development of more targeted and effective biosecurity measures. The eradication effort was challenged by the presence of domestic animals and variability in support for baiting in urbanised areas.

CONCLUSIONS

The results of this study open up new perspectives on island restoration projects. We demonstrated the cost-effectiveness of the action, including ecosystem restoration, reduction of rat impacts in agricultural systems, and improving overall health and food safety. Our findings will have implications for similar interventions on other islands, potentially bringing significant benefits. © 2023 Society of Chemical Industry.

Nest predation of Cory's shearwater Calonectrisborealis (Aves, Procellariiformes) by introduced mammals on Terceira Island, Azores

The Azores holds the largest population of Cory's shearwater Calonectrisborealis (Cory, 1881) (Aves, Procellariiformes) in the world. Apart from a few mammal-free islets, the bulk of the population breeds in coastal areas on the main human-inhabited islands, where several non-native predators have been introduced. Throughout the entire year of the 2019 breeding season, we used motion-triggered cameras and regularly visited three colonies of Cory's shearwater to identify nest predators and the factors affecting nest predation. A total of 292,624 photos were obtained, of which 97.7% were of Cory's shearwaters, 1.7% of non-target species (e.g. other birds, rabbits) and 0.52% of potential predators. Of the monitored nests, 25.7% were predated (n = 9), mainly by black rats (n = 8), but also by cats (n = 1). The relative abundance of black rats in the nests was the main factor explaining nest mortality. This variable was significantly and negatively related with the daily survival rate of Cory's shearwater nestlings. Identification of the main nest predators is crucial for the management and conservation of native bird populations, particularly on oceanic islands, which harbour an important number of threatened and endemic species.

Eurasian beavers in Central Italy: perceptions in the local community

According to the IUCN guidelines, wildlife reintroduction should consider any impacts on humans within feasibility assessments. Eurasian beavers Castor fiber are recovering across their native range, due to protection laws and reintroductions. In Central Italy, a self-sustaining, naturalised population of Eurasian beavers has been identified in the last five years. A questionnaire to measure whether and how citizens in the local area perceive the presence of the beaver was administered to 1114 respondents. We observed a comprehensive awareness of the presence of the beaver in Italy and a high ability to distinguish it from non-native coypus Myocastor coypus (92.3%). We also recorded a general high knowledge of issues related to the presence of the beaver (i.e., potential effects on indigenous biodiversity). The majority (65.5%) of the surveyed population was in favour of reintroducing the beaver in Central Italy, and only 1.2% was firmly against it. The majority of interviewed people was against the removal of beavers from Central Italy (65.8%), whereas only 3.7% was in favor, citing fears of perceived impacts on the river, crops, and fish populations.

Economic costs of protecting islands from invasive alien species

Biological invasions represent a key threat to insular systems and have pronounced impacts across environments and economies. The ecological impacts have received substantial focus, but the socioeconomic impacts are poorly synthesized across spatial and temporal scales. We used the InvaCost database, the most comprehensive assessment of published economic costs of invasive species, to assess economic impacts on islands worldwide. We analyzed socioeconomic costs across differing expenditure types and examined temporal trends across islands that differ in their political geography-island nation states, overseas territories, and islands of continental countries. Over US$36 billion in total costs (including damages and management) has occurred on islands from 1965 to 2020 due to invasive species' impacts. Nation states incurred the greatest total and management costs, and islands of continental countries incurred costs of similar magnitude, both far higher than those in overseas territories. Damage-loss costs were significantly lower, but with qualitatively similar patterns across differing political geographies. The predominance of management spending differs from the pattern found for most countries examined and suggests important knowledge gaps in the extent of many damage-related socioeconomic impacts. Nation states spent the greatest proportion of their gross domestic products countering these costs, at least 1 order of magnitude higher than other locations. Most costs were borne by authorities and stakeholders, demonstrating the key role of governmental and nongovernmental bodies in addressing island invasions. Temporal trends revealed cost increases across all island types, potentially reflecting efforts to tackle invasive species at larger, more socially complex scales. Nevertheless, the already high total economic costs of island invasions substantiate the role of biosecurity in reducing and preventing invasive species arrivals to reduce strains on limited financial resources and avoid threats to sustainable development goals.

Application of genetic and Spatially Explicit Capture-Recapture analyses to design adaptive feral cat control in a large inhabited island

Faunas of oceanic islands have a high proportion of endemic species which contribute to the uniqueness of island communities. Island species are particularly naïve and vulnerable to alien predators, such as cats (Felis catus). On large, inhabited islands, where the complete eradication of feral cat populations is not considered feasible, control represents the best management option to lower their detrimental effects on native fauna. The first objective of our study was to investigate population genetics of feral cats of Réunion Island. The second objective was to understand the space use of feral cats established near the breeding colonies of the two endemic and endangered seabirds of Réunion Island, the Barau’s Petrel (Pterodroma baraui) and the Mascarene Petrel (Pseudobulweria aterrima). We evaluated genetic diversity, population structure and gene flow amongst six groups of feral cats located at a maximum of 10 km from known petrel colonies. We also analysed the behaviour and space use of one of these feral cat groups using camera-trap data and Spatially Explicit Capture-Recapture (SECR) models. Genetic analyses revealed that feral cats were structured in three genetic clusters explained mostly by the island topography. Two clusters were observed at five sampled sites, suggesting high connectivity amongst these sites. The last cluster was found in only one site, suggesting high isolation. This site was a remote mountain area located in the vicinity of one of the main Barau’s Petrel colonies. The behavioural study was conducted on this isolated feral cat population. Mark recapture analysis suggested that feral cats were present at low density and had large home ranges, which is probably explained by reduced food availability. Finally, we make several recommendations for refining feral cat management programmes on inhabited islands.

Herpetofaunal community response to hurricanes Irma and Maria in Virgin Islands National Park

Disturbances are critical for maintaining environmental heterogeneity and biodiversity across landscapes. Hurricanes represent a common disturbance in the Caribbean Sea. These storms are predicted to become more frequent and severe as climate shifts. Understanding how island communities respond to disturbances is critical to their conservation. We surveyed Virgin Islands National Park located on the island of St. John in the Caribbean Sea in 2016 and 2018 to evaluate prolonged herpetofauna community response and resistance to hurricanes. These surveys occurred in March 2016, and June 2018, before and after the 2017 hurricane season, when hurricanes Irma and Maria struck St. John. Using visual encounter surveys, vocalisation surveys, and opportunistic encounters, we surveyed trails within the park through five landscape cover types pre- and post-hurricane. We used linear regression to determine differences in diversity and species richness among landscape cover types and between pre- and post-hurricane surveys and non-metric multidimensional scaling to observe associations among species and landscape cover types pre- and post-hurricane surveys. We determined that there were no significant changes in landscape cover and herpetofauna community associations before and after the 2017 hurricane season, indicating that the herpetofauna communities of Virgin Islands National Park are well adapted to hurricane-related disturbance.

Rapid recolonisation of feral cats following intensive culling in a semi-isolated context

Invasive feral cats threaten biodiversity at a global scale. Mitigating feral cat impacts and reducing their populations has therefore become a global conservation priority, especially on islands housing high endemic biodiversity. The New Caledonian archipelago is a biodiversity hotspot showing outstanding terrestrial species richness and endemism. Feral cats prey upon at least 44 of its native vertebrate species, 20 of which are IUCN Red-listed threatened species. To test the feasibility and efficiency of culling, intensive culling was conducted in a peninsula of New Caledonia (25.6 km²) identified as a priority site for feral cat management. Live-trapping over 38 days on a 10.6 km² area extirpated 36 adult cats, an estimated 44% of the population. However, three months after culling, all indicators derived from camera-trapping (e.g., abundance, minimum number of individuals and densities) suggest a return to pre-culling levels. Compensatory immigration appears to explain this unexpectedly rapid population recovery in a semi-isolated context. Since culling success does not guarantee a long-term effect, complementary methods like fencing and innovative automated traps need to be used, in accordance with predation thresholds identified through modelling, to preserve island biodiversity. Testing general assumptions on cat management, this article contributes important insights into a challenging conservation issue for islands and biodiversity hotspots worldwide.

Identification of the population source of free-ranging cats threatening endemic species on Tokunoshima Island, Japan

Free-ranging cats Felis silvestris catus are harmful to endemic species, especially on islands. Effective management practices require an understanding of their habitat use and population source at the landscape level. We aimed to identify the source of the free-ranging cat population on Tokunoshima Island, Japan, which harbors a variety of endemic organisms as well as human settlements. Trapping data for the whole island were provided by local governments, and landscape factors (residential, agricultural, and woodlot areas and cattle barn density) affecting cat density were explored. An analysis of live-capture data indicated that the density (per 1 km2) of free-ranging cats was positively correlated with the densities of cattle barns and woodlot areas and negatively correlated with residential areas. An interview survey revealed that nearly half of the cattle barns feed free-ranging cats. The source habitat of free-ranging cats appears to be areas with a high density of cattle barns and a high percentage of woodlots in human-dominated landscapes. Feeding cats in cattle barns may strengthen the bottom-up process of population growth on the island. To reduce the impact of cats on endemic species on Tokunoshima Island, efforts to stop feeding cats in cattle barns are important. Reaching a consensus with stakeholders will require further studies of the ecological risks posed by free-ranging cats.

Biosecurity risks posed by a large sea-going passenger vessel: challenges of terrestrial arthropod species detection and eradication

Large sea-going passenger vessels can pose a high biosecurity risk. The risk posed by marine species is well documented, but rarely the risk posed by terrestrial arthropods. We conducted the longest running, most extensive monitoring program of terrestrial arthropods undertaken on board a passenger vessel. Surveillance was conducted over a 19-month period on a large passenger (cruise) vessel that originated in the Baltic Sea (Estonia). The vessel was used as an accommodation facility to house workers at Barrow Island (Australia) for 15 months, during which 73,061 terrestrial arthropods (222 species - four non-indigenous (NIS) to Australia) were collected and identified on board. Detection of Tribolium destructor Uytt., a high-risk NIS to Australia, triggered an eradication effort on the vessel. This effort totalled more than 13,700 human hours and included strict biosecurity protocols to ensure that this and other non-indigenous species (NIS) were not spread from the vessel to Barrow Island or mainland Australia. Our data demonstrate that despite the difficulties of biosecurity on large vessels, stringent protocols can stop NIS spreading from vessels, even where vessel-wide eradication is not possible. We highlight the difficulties associated with detecting and eradicating NIS on large vessels and provide the first detailed list of species that inhabit a vessel of this kind.

Rodent gene drives for conservation: opportunities and data needs

Invasive rodents impact biodiversity, human health and food security worldwide. The biodiversity impacts are particularly significant on islands, which are the primary sites of vertebrate extinctions and where we are reaching the limits of current control technologies. Gene drives may represent an effective approach to this challenge, but knowledge gaps remain in a number of areas. This paper is focused on what is currently known about natural and developing synthetic gene drive systems in mice, some key areas where key knowledge gaps exist, findings in a variety of disciplines relevant to those gaps and a brief consideration of how engagement at the regulatory, stakeholder and community levels can accompany and contribute to this effort. Our primary species focus is the house mouse, Mus musculus, as a genetic model system that is also an important invasive pest. Our primary application focus is the development of gene drive systems intended to reduce reproduction and potentially eliminate invasive rodents from islands. Gene drive technologies in rodents have the potential to produce significant benefits for biodiversity conservation, human health and food security. A broad-based, multidisciplinary approach is necessary to assess this potential in a transparent, effective and responsible manner.

Anticoagulant Rodenticides, Islands and Animal Welfare Accountancy

Simple Summary

Anticoagulant rodenticides are a mainstay of rodent management in many domestic, municipal, agricultural, and conservation settings. Anticoagulant poisoning has poor welfare outcomes for mammals and birds and, worldwide, this means potentially very large numbers of animals are poisoned annually consequent (intended or not) to rodenticide use. Critical differences in use patterns of anticoagulants applied for ongoing rodent control, versus application for rodent eradication especially on islands, have clear implications for animal welfare costs measured as cumulative number of animals affected over time. Here we outline these differences and discuss how animal welfare considerations can be weighed in decisions to use anticoagulant rodenticides for island eradication attempts.

Abstract

Anticoagulant rodenticides are used to manage rodents in domestic, municipal, agricultural, and conservation settings. In mammals and birds, anticoagulant poisoning causes extensive hemorrhagic disruption, with the primary cause of death being severe internal bleeding occurring over days. The combined severity and duration of these effects represent poor welfare outcomes for poisoned animals. Noting a lack of formal estimates of numbers of rodents and nontarget animals killed by anticoagulant poisoning, the ready availability and worldwide use of anticoagulants suggest that very large numbers of animals are affected globally. Scrutiny of this rodent control method from scientific, public, and regulatory perspectives is being driven largely by mounting evidence of environmental transfer of residual anticoagulants resulting in harmful exposure in wild or domestic animals, but there is also nascent concern for the welfare of targeted rodents. Rodent control incurs a cumulative ledger of animal welfare costs over time as target populations reduced by poisoning eventually recover to an extent requiring another reduction. This ‘rolling toll’ presents a critical contrast to the animal welfare accountancy ledger for eradication scenarios, where rodent populations can be completely removed by methods including anticoagulant use and then kept from coming back (e.g., on islands). Successful eradications remove any future need to control rodents and to incur the associated animal welfare costs.

Biological control of pests and a social model of animal welfare

This paper considers the sociocultural implications of biological pest control that sit at the cusp of managing an invasive species for conservation or productivity (i.e. a 'natural enemy') and socially driven 'manipulating life' arguments. We consider the role of perceived humaneness or, more accurately, animal welfare as it relates to managing invasive species from a scientific and social perspective. In order to highlight and articulate particular nuances and standards across different pest control contexts, we use three case examples (feral cats, wild rabbits, and invasive cane toads) and explore where biological pest control and animal welfare interests intersect. The paper summarises key scientific welfare concerns and then extends the literature to also examine key social characteristics of each pest management scenario, including lay perceptions of animal welfare, the sociocultural context that pests exist within, and overarching psychological factors contributing to public sentiment, including perceived risks. The subsequent descriptive model presented is useful in articulating core sociocultural beliefs relative to each case and how these antecedent associations and attitudes about an animal influence subsequent beliefs about a pest management strategy and ultimately acceptance of the management approach. The model can inform invasive species management policies and highlight key sociocultural factors likely to influence public responses. The model also informs interdisciplinary science designed to develop acceptable and socially responsible biocontrol strategies that consider public perceptions of animal welfare and cultural appropriateness.

Globally important islands where eradicating invasive mammals will benefit highly threatened vertebrates

Invasive alien species are a major threat to native insular species. Eradicating invasive mammals from islands is a feasible and proven approach to prevent biodiversity loss. We developed a conceptual framework to identify globally important islands for invasive mammal eradications to prevent imminent extinctions of highly threatened species using biogeographic and technical factors, plus a novel approach to consider socio-political feasibility. We applied this framework using a comprehensive dataset describing the distribution of 1,184 highly threatened native vertebrate species (i.e. those listed as Critically Endangered or Endangered on the IUCN Red List) and 184 non-native mammals on 1,279 islands worldwide. Based on extinction risk, irreplaceability, severity of impact from invasive species, and technical feasibility of eradication, we identified and ranked 292 of the most important islands where eradicating invasive mammals would benefit highly threatened vertebrates. When socio-political feasibility was considered, we identified 169 of these islands where eradication planning or operation could be initiated by 2020 or 2030 and would improve the survival prospects of 9.4% of the Earth's most highly threatened terrestrial insular vertebrates (111 of 1,184 species). Of these, 107 islands were in 34 countries and territories and could have eradication projects initiated by 2020. Concentrating efforts to eradicate invasive mammals on these 107 islands would benefit 151 populations of 80 highly threatened vertebrates and make a major contribution towards achieving global conservation targets adopted by the world's nations.

Havens for threatened Australian mammals: the contributions of fenced areas and offshore islands to the protection of mammal species susceptible to introduced predators

Context Many Australian mammal species are highly susceptible to predation by introduced domestic cats (Felis catus) and European red foxes (Vulpes vulpes). These predators have caused many extinctions and have driven large distributional and population declines for many more species. The serendipitous occurrence of, and deliberate translocations of mammals to, ‘havens’ (cat- and fox-free offshore islands, and mainland fenced exclosures capable of excluding cats and foxes) has helped avoid further extinction. Aims The aim of this study was to conduct a stocktake of current island and fenced havens in Australia and assess the extent of their protection for threatened mammal taxa that are most susceptible to cat and fox predation. Methods Information was collated from diverse sources to document (1) the locations of havens and (2) the occurrence of populations of predator-susceptible threatened mammals (naturally occurring or translocated) in those havens. The list of predator-susceptible taxa (67 taxa, 52 species) was based on consensus opinion from >25 mammal experts. Key results Seventeen fenced and 101 island havens contain 188 populations of 38 predator-susceptible threatened mammal taxa (32 species). Island havens cover a larger cumulative area than fenced havens (2152km2 versus 346km2), and reach larger sizes (largest island 325km2, with another island of 628km2 becoming available from 2018; largest fence: 123km2). Islands and fenced havens contain similar numbers of taxa (27 each), because fenced havens usually contain more taxa per haven. Populations within fences are mostly translocated (43 of 49; 88%). Islands contain translocated populations (30 of 139; 22%); but also protect in situ (109) threatened mammal populations. Conclusions Havens are used increasingly to safeguard threatened predator-susceptible mammals. However, 15 such taxa occur in only one or two havens, and 29 such taxa (43%) are not represented in any havens. The taxon at greatest risk of extinction from predation, and in greatest need of a haven, is the central rock-rat (Zyzomys pedunculatus). Implications Future investment in havens should focus on locations that favour taxa with no (or low) existing haven representation. Although havens can be critical for avoiding extinctions in the short term, they cover a minute proportion of species’ former ranges. Improved options for controlling the impacts of cats and foxes at landscape scales must be developed and implemented.

Globally threatened vertebrates on islands with invasive species

Global biodiversity loss is disproportionately rapid on islands, where invasive species are a major driver of extinctions. To inform conservation planning aimed at preventing extinctions, we identify the distribution and biogeographic patterns of highly threatened terrestrial vertebrates (classified by the International Union for Conservation of Nature) and invasive vertebrates on ~465,000 islands worldwide by conducting a comprehensive literature review and interviews with more than 500 experts. We found that 1189 highly threatened vertebrate species (319 amphibians, 282 reptiles, 296 birds, and 292 mammals) breed on 1288 islands. These taxa represent only 5% of Earth's terrestrial vertebrates and 41% of all highly threatened terrestrial vertebrates, which occur in <1% of islands worldwide. Information about invasive vertebrates was available for 1030 islands (80% of islands with highly threatened vertebrates). Invasive vertebrates were absent from 24% of these islands, where biosecurity to prevent invasions is a critical management tool. On the 76% of islands where invasive vertebrates were present, management could benefit 39% of Earth's highly threatened vertebrates. Invasive mammals occurred in 97% of these islands, with Rattus sp. as the most common invasive vertebrate (78%; 609 islands). Our results provide an important baseline for identifying islands for invasive species eradication and other island conservation actions that reduce biodiversity loss.

Estimating Burdens of Neglected Tropical Zoonotic Diseases on Islands with Introduced Mammals

Many neglected tropical zoonotic pathogens are maintained by introduced mammals, and on islands the most common introduced species are rodents, cats, and dogs. Management of introduced mammals, including control or eradication of feral populations, which is frequently done for ecological restoration, could also reduce or eliminate the pathogens these animals carry. Understanding the burden of these zoonotic diseases is crucial for quantifying the potential public health benefits of introduced mammal management. However, epidemiological data are only available from a small subset of islands where these introduced mammals co-occur with people. We examined socioeconomic and climatic variables as predictors for disease burdens of angiostrongyliasis, leptospirosis, toxoplasmosis, toxocariasis, and rabies from 57 islands or island countries. We found strong correlates of disease burden for leptospirosis, Toxoplasma gondii infection, angiostrongyliasis, and toxocariasis with more than 50% of the variance explained, and an average of 57% (range = 32-95%) predictive accuracy on out-of-sample data. We used these relationships to provide estimates of leptospirosis incidence and T. gondii seroprevalence infection on islands where nonnative rodents and cats are present. These predicted estimates of disease burden could be used in an initial assessment of whether the costs of managing introduced mammal reservoirs might be less than the costs of perpetual treatment of these diseases on islands.

Invasive mammal eradication on islands results in substantial conservation gains

More than US$21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations) were negatively impacted by invasive mammal eradication. Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category. We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List-6% of all these highly threatened species-likely have benefitted from invasive mammal eradications on islands. Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here. Our results highlight the importance of invasive mammal eradication on islands for protecting the world's most imperiled fauna.

Reducing the primary exposure risk of Henderson crakes (Zapornia atra) during aerial broadcast eradication by selecting appropriate bait colour

Context Operations to eradicate non-native invasive predators from islands frequently put native species at risk of consuming harmful substances, such as poison bait. The incorporation of certain colours in poison-bait pellets may reduce the risk of bait consumption and, therefore, non-target mortality. Previous work indicated that birds generally avoid blue or green colours; however, there is substantial inter-specific variation in this preference, and more experimental work on species of conservation concern is needed. Aims We tested whether a globally threatened island endemic, the Henderson crake (Zapornia atra), which suffered substantial mortality during a rat-eradication attempt on Henderson Island in 2011, would consume fewer blue than green pellets, which were used during the previous eradication attempt. Methods We held 22 Henderson crakes in captivity and provided them with either blue or green non-toxic pellets for 5 days in June and July 2015. We measured consumption and used linear mixed models to evaluate whether bait colour influenced consumption. Key results Henderson crakes did not consume any dry pellets, and all trials were conducted with wet bait pellets. We found slightly lower consumption of blue pellets than green pellets, and substantial variation among individuals. Females (n = 17) consumed 24% less blue than green bait, whereas males (n = 5) consumed 77% less blue than green bait. Conclusion Henderson crakes are unlikely to consume dry pellets, and will likely consume fewer blue than green bait pellets. Implications We recommend that any future rat eradication on Henderson Island considers using blue rather than green baits and targets dry weather to reduce the risk of Henderson crakes consuming toxic rodenticide bait pellets.

Integrating biology into invasive species management is a key principle for eradication success: the case of yellow crazy ant Anoplolepis gracilipes in northern Australia

The lack of biological knowledge of many invasive species remains as one of the greatest impediments to their management. Here I detail targeted research into the biology of the yellow crazy ant Anoplolepis gracilipes within northern Australia and detail how such knowledge can be used to improve the management outcomes for this species. I quantified nest location and density in three habitats, worker activity over 24 h, infestation expansion rate, seasonal variation of worker abundance and the timing of production of sexuals. Nests were predominantly (up to 68%) located at the bases of large trees, indicating that search efforts should focus around tree bases. Nest density was one nest per 22, 7.1 and 6.3 m2 in the three habitats, respectively. These data form the baselines for quantifying treatment efficacy and set sampling densities for post-treatment assessments. Most (60%) nests were underground, predominantly (89%) occurring in an open area rather than underneath a rock or log. Some seasonality was evident for nests within leaf litter, with most (83%) occurring during the 'wet season' (October-March). Of the underground nests, most were shallow, with 44% being less than 10 cm deep, and 67% being less than 20 cm deep. Such nest location and density information serves many management purposes, for improving detection, mapping and post-treatment assessments, and also provided strong evidence that carbohydrate supply was a major driver of A. gracilipes populations. Just over half of the nests (56%) contained queens. Of the 62 underground nests containing queens, most queens (80%) were located at the deepest chamber. When queens were present, most often (38%) only one queen was present, the most being 16. Queen number per nest was the lowest in July and August just prior to the emergence of virgin queens in September, with queen numbers then remaining steadily high until April. Nothing is known for any ant species about how the queen number per nest/colony affects treatment efficacy, but further research would no doubt yield important breakthroughs for treating ants. Activity occurred predominantly nocturnally, ceasing during mid-day. These activity data determined the critical threshold above which work must be conducted to be considered reliable, and also suggests that treatments are best applied in the afternoon. Total brood production peaked in February and was the lowest around August and September. These abundance data form the baselines for quantifying treatment efficacy, and may have implications for treatment efficacy. Males were found every month, predominantly between August and November. Queen pupae were found in September. The reproductive timing of sexuals determines the treatment schedule. Targeted, site-specific research such as that described here should be an integral part of any eradication program for invasive species to design knowledge-based treatment protocols and determine assessment benchmarks.

The effect of scientific evidence on conservation practitioners' management decisions

A major justification of environmental management research is that it helps practitioners, yet previous studies show it is rarely used to inform their decisions. We tested whether conservation practitioners focusing on bird management were willing to use a synopsis of relevant scientific literature to inform their management decisions. This allowed us to examine whether the limited use of scientific information in management is due to a lack of access to the scientific literature or whether it is because practitioners are either not interested or unable to incorporate the research into their decisions. In on-line surveys, we asked 92 conservation managers, predominantly from Australia, New Zealand, and the United Kingdom, to provide opinions on 28 management techniques that could be applied to reduce predation on birds. We asked their opinions before and after giving them a summary of the literature about the interventions' effectiveness. We scored the overall effectiveness and certainty of evidence for each intervention through an expert elicitation process-the Delphi method. We used the effectiveness scores to assess the practitioners' level of understanding and awareness of the literature. On average, each survey participant changed their likelihood of using 45.7% of the interventions after reading the synopsis of the evidence. They were more likely to implement effective interventions and avoid ineffective actions, suggesting that their intended future management strategies may be more successful than current practice. More experienced practitioners were less likely to change their management practices than those with less experience, even though they were not more aware of the existing scientific information than less experienced practitioners. The practitioners' willingness to change their management choices when provided with summarized scientific evidence suggests that improved accessibility to scientific information would benefit conservation management outcomes.

Prioritizing islands for the eradication of invasive vertebrates in the United Kingdom overseas territories

Invasive alien species are one of the primary threats to native biodiversity on islands worldwide. Consequently, eradicating invasive species from islands has become a mainstream conservation practice. Deciding which islands have the highest priority for eradication is of strategic importance to allocate limited resources to achieve maximum conservation benefit. Previous island prioritizations focused either on a narrow set of native species or on a small geographic area. We devised a prioritization approach that incorporates all threatened native terrestrial vertebrates and all invasive terrestrial vertebrates occurring on 11 U.K. overseas territories, which comprise over 2000 islands ranging from the sub-Antarctic to the tropics. Our approach includes eradication feasibility and distinguishes between the potential and realistic conservation value of an eradication, which reflects the benefit that would accrue following eradication of either all invasive species or only those species for which eradication techniques currently exist. We identified the top 25 priority islands for invasive species eradication that together would benefit extant populations of 155 native species including 45 globally threatened species. The 5 most valuable islands included the 2 World Heritage islands Gough (South Atlantic) and Henderson (South Pacific) that feature unique seabird colonies, and Anegada, Little Cayman, and Guana Island in the Caribbean that feature a unique reptile fauna. This prioritization can be rapidly repeated if new information or techniques become available, and the approach could be replicated elsewhere in the world.

The biogeography of globally threatened seabirds and island conservation opportunities

Seabirds are the most threatened group of marine animals; 29% of species are at some risk of extinction. Significant threats to seabirds occur on islands where they breed, but in many cases, effective island conservation can mitigate these threats. To guide island-based seabird conservation actions, we identified all islands with extant or extirpated populations of the 98 globally threatened seabird species, as recognized on the International Union for Conservation of Nature Red List, and quantified the presence of threatening invasive species, protected areas, and human populations. We matched these results with island attributes to highlight feasible island conservation opportunities. We identified 1362 threatened breeding seabird populations on 968 islands. On 803 (83%) of these islands, we identified threatening invasive species (20%), incomplete protected area coverage (23%), or both (40%). Most islands with threatened seabirds are amenable to island-wide conservation action because they are small (57% were <1 km(2) ), uninhabited (74%), and occur in high- or middle-income countries (96%). Collectively these attributes make islands with threatened seabirds a rare opportunity for effective conservation at scale.