Other environmental factors affects more Island foxes diet than competition with feral cats

Cypher, B.L. , Kelly E.C., Ferrara, F.J., Drost C.A., Westall, T.L. & Hudgens, B.R. 2017. Diet patterns of island foxes on San Nicolas Island relative to feral cat removal. Pacific Conservation Biology 23(2) 180-188

Island foxes (Urocyon littoralis) are a species of conservation concern that occur on six of the Channel Islands off the coast of southern California. We analysed island fox diet on San Nicolas Island during 2006–12 to assess the influence of the removal of feral cats (Felis catus) on the food use by foxes. Our objective was to determine whether fox diet patterns shifted in response to the cat removal conducted during 2009–10, thus indicating that cats were competing with foxes for food items. We also examined the influence of annual precipitation patterns and fox abundance on fox diet. On the basis of an analysis of 1975 fox scats, use of vertebrate prey – deer mice (Peromyscus maniculatus), birds, and lizards – increased significantly during and after the complete removal of cats (n = 66) from the island. Deer mouse abundance increased markedly during and after cat removal and use of mice by foxes was significantly related to mouse abundance. The increase in mice and shift in item use by the foxes was consistent with a reduction in exploitative competition associated with the cat removal. However, fox abundance declined markedly coincident with the removal of cats and deer mouse abundance was negatively related to fox numbers. Also, annual precipitation increased markedly during and after cat removal and deer mouse abundance closely tracked precipitation. Thus, our results indicate that other confounding factors, particularly precipitation, may have had a greater influence on fox diet patterns.

Progress in the eradication of the feral cat and recovery of the native fauna on Socorro Is

Ortiz-Alcaraz, A., Aguirre-Muñoz, A., Arnaud, G., Galina-Tessaro, P., Rojas-Mayoral, E., Méndez-Sánchez, F., & Ortega-Rubio, A. (2017). Progress in the eradication of the feral cat (Felis catus) and recovery of the native fauna on Socorro Island, Revillagigedo Archipelago, Mexico. Therya, 8(1).

Socorro Island, in the Revillagigedo Archipelago, has the highest number of endemisms of any Mexican island. It provides habitat for 117 vascular plants, 26 % of which are endemic to the island. Also endemic to the island are one reptile and eight terrestrial bird species. However, the local ecosystem has been heavily degraded by exotic mammals over the past 140 years. The feral sheep (Ovis aries) has contributed to a 30% loss in habitat based on the island’s surface area. Another serious threat is the feral cat (Felis catus), which has severely impacted the island’s bird communities and the endemic Socorro tree lizard (Urosaurus auriculatus). 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 pose a serious threat for other vulnerable species, such as the Townsend’s shearwater (Puffinus auricularis). The feral sheep was completely eradicated in 2012, which resulted in a rapid and remarkable recovery of the local vegetation cover. The eradication of the feral cat has been a complex issue to undertake due to the large size and topographical complexity of Socorro Island. In 2011 Grupo de Ecología y Conservacion de Islas, A. C. (GECI) started a feral cat control program, which scaled up into an eradication campaign. Here we report on the progress of the eradication campaign between 2011 and 2015, and provide a first assessment of the recovery of the native fauna. Beginning in 2011, camera traps were used to estimate cat abundance. Leg-hold and lethal traps were used to capture feral cats, some of them mounted with telemetry devices that alerted when traps were activated. Native vertebrates were monitored to confirm the positive effects derived from cat control efforts. By July 2015, 413 cats were dispatched using soft leg-hold and lethal traps, with a combined effort of 22,706 trap-nights. To date (mid-2016), cat abundance has decreased significantly, with cats being completely absent for several years in different areas of the island. The abundance of the endemic Socorro Island tree lizard and terrestrial birds has increased thanks to significant progress. Completing this important conservation action requires an increase in trapping efforts and the use of detection dogs, combined with night hunting. We estimate that the eradication of the feral cat will be completed by early 2017, after which the absence confirmation phase will begin.

Reduction in the capture success (%) of feral cats in the rainy and dry seasons from 2012 to 2015.

High-impact conservation: invasive mammal eradications from the islands of western Mexico

Aguirre-Muñoz, A., Croll, D. A., Donlan, C. J., Henry III, R. W., Hermosillo, M. A., Howald, G. R., ... & Samaniego-Herrera, A. (2008). High-impact conservation: invasive mammal eradications from the islands of western Mexico. AMBIO: A Journal of the Human Environment, 37(2), 101-107.

Islands harbor a disproportionate amount of the earth's biodiversity, but a significant portion has been lost due in large part to the impacts of invasive mammals. Fortunately, invasive mammals can be routinely removed from islands, providing a powerful tool to prevent extinctions and restore ecosystems. Given that invasive mammals are still present on more than 80% of the world's major islands groups and remain a premier threat to the earth's biodiversity, it is important to disseminate replicable, scaleable models to eradicate invasive mammals from islands. We report on a successful model from western México during the past decade. A collaborative effort between nongovernmental organizations, academic biologists, Mexican government agencies, and local individuals has resulted in major restoration efforts in three island archipelagos. Forty-two populations of invasive mammals have been eradicated from 26 islands. For a cost of USD 21 615 per colony and USD 49 370 per taxon, 201 seabird colonies and 88 endemic terrestrial taxa have been protected, respectively. These conservation successes are a result of an operational model with three main components: i) a tri-national collaboration that integrates research, prioritization, financing, public education, policy work, capacity building, conservation action, monitoring, and evaluation; ii) proactive and dedicated natural resource management agencies; and iii) effective partnerships with academic researchers in México and the United States. What is now needed is a detailed plan to eradicate invasive mammals from the remaining islands in the region that integrates the needed additional financing, capacity, technical advances, and policy issues. Island conservation in western México provides an effective approach that can be readily applied to other archipelagos where conservation efforts have been limited.

Cats among the most usual targets of eradication programs on islands

Jones, H. P., Holmes, N. D., Butchart, S. H., Tershy, B. R., Kappes, P. J., Corkery, I., ... & Campbell, K. (2016). Invasive mammal eradication on islands results in substantial conservation gains. Proceedings of the National Academy of Sciences, 201521179.

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.

Prioritizing mammal eradication actions on islands: it's not all or nothing

Helmstedt, K. J., Shaw, J. D., Bode, M., Terauds, A., Springer, K., Robinson, S. A., & Possingham, H. P. (2016). Prioritizing eradication actions on islands: it's not all or nothing. Journal of Applied Ecology.

1. Many highly diverse island ecosystems across the globe are threatened by invasive species. Eradications of invasive mammals from islands are being attempted with increasing frequency, with success aided by geographical isolation and increasing knowledge of eradication techniques. There have been many attempts to prioritize islands for invasive species eradication; however, these coarse methods all assume managers are unrealistically limited to a single action on each island: either eradicate all invasive mammals, or do nothing.
2. We define a prioritization method that broadens the suite of actions considered, more accurately representing the complex decisions facing managers. We allow the opportunity to only eradicate a subset of invasive mammals from each island, intentionally leaving some invasive mammals on islands. We consider elements often omitted in previous prioritization methods, including feasibility, cost and complex ecological responses (i.e. trophic cascades).
3. Using a case study of Australian islands, we show that for a fixed budget, this method can provide a higher conservation benefit across the whole group of islands. Our prioritization method outperforms simpler methods for almost 80% of the budgets considered.
4. On average, by relaxing the restrictive assumption that an eradication attempt must be made for all invasives on an island, ecological benefit can be improved by 27%.
5. Synthesis and applications. Substantially higher ecological benefits for threatened species can be achieved for no extra cost if conservation planners relax the assumption that eradication projects must target all invasives on an island. It is more efficient to prioritize portfolios of eradication actions rather than islands.

Little recovery of burrowing petrels after cat eradication

Cerfonteyn, M., & Ryan, P. G. 2016. Have burrowing petrels recovered on Marion Island two decades after cats were eradicated? Evidence from sub-Antarctic skua prey remains. Antarctic Science, 1-7.

In the 1980s, penguins dominated the prey remains of sub-Antarctic skuas Stercorarius antarcticus breeding on Marion Island, whereas on neighbouring Prince Edward Island burrowing petrels made up >95% of prey remains in nest middens. This difference resulted at least in part from the impact of introduced cats Felis catus on Marion Island’s burrowing petrel populations. Cats were introduced to Marion Island in 1949, and prior to their eradication in 1991, they killed an estimated 450 000 petrels each year, greatly reducing the densities of petrels breeding on the island. A repeat survey of skua prey remains showed that penguins still dominated the prey of breeding sub-Antarctic skuas on Marion Island in the summer of 2010–11, two decades after cats were eradicated from the island. The proportion of penguin remains decreased slightly compared to 1987–88, but this might be expected given the decreases in penguin numbers on Marion Island over this period. Regurgitated pellets confirmed the dominance of penguin prey on Marion Island. Taken together with the decrease in skua numbers on Marion Island over the last two decades, our results suggest that there has been little recovery in the population of at least summer-breeding burrowing petrels since cats were eradicated.

Modelling eradication of feral cats

Beeton, N. J., McMahon, C. R., Williamson, G. J., Potts, J., Bloomer, J., Bester, M. N., ... & Johnson, C. N. (2015). Using the Spatial Population Abundance Dynamics Engine for conservation management. Methods in Ecology and Evolution.

1. An explicit spatial understanding of population dynamics is often critical for effective management of wild populations. Sophisticated approaches are available to simulate these dynamics, but are largely either spatially homogeneous or agent based, and thus best suited to small spatial or temporal scales. These approaches also often ignore financial decisions crucial to choosing management approaches on the basis of cost-effectiveness.
2. We created a user-friendly and flexible modelling framework for simulating these population issues at large spatial scales – the Spatial Population Abundance Dynamics Engine (SPADE). SPADE is based on the Spatio-Temporal Animal Reduction (STAR) model (McMahon et al. 2010) and uses a reaction–diffusion approach to model population trajectories and a cost-benefit analysis technique to calculate optimal management strategies over long periods and across broad spatial scales. It expands on STAR by incorporating species interactions and multiple concurrent management strategies, and by allowing full user control of functional forms and parameters.
3. We used SPADE to simulate the eradication of feral domestic cats Felis catus on sub-Antarctic Marion Island (Bester et al., South African Journal of Wildlife Research, 32, 2002, 65) and compared modelled outputs to observed data. The parameters of the best-fitting model reflected the conditions of the management programme, and the model successfully simulated the observed movement of the cat population to the southern and eastern portion of the island under hunting pressure. We further demonstrated that none of the management strategies would likely have been successful within a reasonable time frame if performed in isolation.
4. Spatial Population Abundance Dynamics Engine is applicable to a wide range of population management problems and allows easy generation, modification and analysis of management scenarios. It is a useful tool for the planning, evaluation and optimisation of the management of wild populations and can be used without specialised training.

Different cat diet between islands

Bonnaud, E., Palmas, P., Bourgeois, K., Ollier, S., Zarzoso-Lacoste, D., & Vidal, E. (2015). Island specificities matter: cat diet differs significantly between islands of a major breeding archipelago for a vulnerable endemic seabird. Biological Invasions, 1-15.

Domestic cats are one of the most widespread predators on islands worldwide and are responsible for numerous reductions and extinctions of species on islands. The three main islands of the Hyères Archipelago house one of the largest colonies of the Mediterranean endemic Yelkouan shearwater Puffinus yelkouan that has recently been up-listed by the IUCN to ‘vulnerable’. The main objectives of this study were to assess the diet of cats and to study the effect of cat predation on Yelkouan shearwater populations at the archipelago scale. The diet of cats was studied using scat analyses according to years and seasons for each island. Simultaneously, Yelkouan shearwater breeding success was monitored during a period of 8 years on Port-Cros and Porquerolles, and 3 years on Le Levant. Descriptive analyses and GLM were used to compare data gathered on each island. At the archipelago scale, cats preyed strongly upon introduced mammals and shearwaters. Surprisingly, large differences appeared in cats’ diet according to the island considered. The Yelkouan shearwater was the primary prey of cats on Le Levant, but secondary on Port-Cros and Porquerolles. Cat predation was mainly concentrated during the shearwater prospecting period, when birds arrive at the colonies and look for a mate (if they are not already paired) and a burrow before breeding. Consequently cat impact was low on shearwater breeding success. However, this study demonstrates that the cat management conducted on Port-Cros was positive for fledging success. The successful cat eradication on Port-Cros supports the need to continue working for Yelkouan shearwater conservation with Le Levant as a priority, because this is where the colonies are largest and predation on Yelkouan shearwaters is very high.

Ecological Restoration of sub-Antarctic Macquarie Island

Springer, K. Ecological Restoration of sub-Antarctic Macquarie Island.

Invasive vertebrate species have had devastating impacts on the flora, fauna and landforms of Macquarie Island over a period of 200 years. Following the successful eradication of weka (Gallirallus australis) by 1989 and feral cats (Felis catus) by 2001, planning for the eradication of ship rats (Rattus rattus), house mice (Mus musculus) and European rabbits (Oryctolagus cuniculus) began in 2004. Funding of AUD$24.7M was secured in 2007 for a multi-year project based on aerial baiting targeting rabbits and rodents followed by ground hunting targeting surviving rabbits. The first aerial baiting attempt in 2010 was abandoned due to unfavourable weather and shipping delays. The degree of non-target seabird species mortality from limited baiting in 2010 lead to a renewed examination of non-target mitigation options. Rabbit Haemorrhagic Disease Virus (RHDV) was introduced in February 2011, to reduce the pre-baiting rabbit population and thus minimise non-target mortality amongst scavenging seabirds. Aerial baiting resumed in May 2011 using four AS350 helicopters and a team of 27 people, and was completed by July 2011. No rodents have been detected post-baiting and the estimated rabbit population of 150,000 has been reduced to fewer than 30 at the conclusion of baiting The rabbit hunting phase commenced in July 2011 using a team of 15 hunters and 12 dogs and is ongoing, with thirteen rabbits accounted for. Hunting and monitoring is expected to take a total of five years post-baiting and will be based on annual progress reviews. A minimum of two years monitoring will be conducted. Rodent detection dogs will deploy in 2013 to assist in determining rodent eradication success.
Six months after baiting, vegetation recovery was already evident and increased burrownesting seabird activity has also been observed in the first breeding season post-baiting.

Optimal multispecies eradication schedules for a commonly encountered invaded island ecosystem

Bode, M., Baker, C. M., & Plein, M. (2015). Eradicating down the food chain: optimal multispecies eradication schedules for a commonly encountered invaded island ecosystem. Journal of Applied Ecology, 52(3), 571-579.

Islands are global hotspots of both biodiversity and extinction. Invasive species are a primary threat, and the majority of islands have been invaded by more than one. Multispecies eradications are essential for conserving the biodiversity of these islands, but experience has shown that eradicating species at the wrong time can be disastrous for endemic species.
Managers not only have to decide how to eradicate each invasive species, they need to determine when to target each species, and how to control multiple species with a limited budget. We use dynamic control theory to show that, when resources are limited, species should be eradicated in a particular order (an eradication schedule). We focus on a common invaded island ecosystem motif, where one invasive predator consumes two prey species (one endemic, one invasive), and managers wish to eradicate both invasives while ensuring the persistence of the endemic species. We identify the optimal eradication schedule for this entire class of problem. To illustrate the application of our solution, we also analyse a particular case study from California's Channel Islands.
For any island ecosystem that shares this motif, managers should begin by allocating all of their resources towards invasive predator control. Only later should resources be shifted towards controlling the invasive prey. This shift should ideally be gradual, but an abrupt shift is very close to optimal. The Channel Islands case study confirms these findings. Targeting both species simultaneously is substantially suboptimal.
We reach the robust conclusion that the same eradication schedule should be applied to any island with this ecosystem motif, even if the ecosystem contains different species to the Channel Islands case study.
Synthesis and applications. Although very numerous, the world's invaded island ecosystems could be described by a limited range of invaded ecosystem motifs. By calculating robust optimal eradication schedules for each motif, the approach defined in this study could offer rapid decision-support for a large number of future conservation projects where specific data are scarce.

Macquarie Is. eradication accomplished

Mission Accomplished - Landline - ABC

Long-term protection of seabird breeding colonies on Tasman Island through eradication of cats

Robinson, S., Gadd, L., Johnston, M., & Pauza, M. (2015). Long-term protection of important seabird breeding colonies on Tasman Island through eradication of cats. New Zealand Journal of Ecology, 39(2), 0-0.

A restoration programme was initiated in 2008 in response to high levels of seabird predation by feral cats (Felis catus) at Australia’s largest fairy prion (Pachyptila turtur) colony on Tasman Island, Tasmania. The primary knockdown involved aerial baiting with para-aminopropiophenone (PAPP) in meat baits. The efficacy of baiting was lower than expected resulting in trapping and hunting commencing earlier than planned. Cats were successfully eradicated over two weeks. Key to the success of the programme was the identification of a narrow window of low prey availability for cats. Post-eradication monitoring of the two most common seabird species, fairy prions and short-tailed shearwaters (Ardenna tenuirostris), showed positive signs towards population recovery. Prion activity increased three-fold and shearwater breeding success increased.

Tasmanian farmers and environmentalists team up to eradicate feral cat threat

From http://www.abc.net.au/

Farmers and environmentalists in northern Tasmania are teaming up to eradicate feral cats blamed for killing more than 20 billion native Australian animals a year, as well as threatening livestock ... continue reading

Floreana Island rodent and cat eradication feasibility analysis

Island Conservation (2013) Floreana Island Ecological Restoration: Rodent and Cat Eradication
Feasibility Analysis version 6.0. Island Conservation, Santa Cruz, California. 85 pp.

The eradication of introduced vertebrates has become a widely accepted strategy for restoring island ecosystems. Based on an understanding of eradication methods and the Floreana Island project site, the feasibility of removing black rats, house mice, and feral cats is assessed within this document. Feasibility was assessed based on current techniques to safely remove rodents and feral cats from islands which have been used worldwide, including recent eradications within the Galápagos archipelago.
The goal of this project is to restore ecosystem function as well as enhance community well-being on Floreana Island. This would be achieved through the eradication of black rats, house mice and feral cats and by implementing effective biosecurity measures (e.g. preventing a rodent incursion and ensuring that domestic cats present on the island cannot act as a source population).
The most common technique used globally for removing rodents from islands is the application of bait containing a rodenticide. Cats are primarily targeted with poison, trapping, and hunting. Floreana is a large island (17,125 ha) compared to efforts undertaken elsewhere. If successful, it would be the second largest island to have had cats and rats removed and the largest to have had mice removed. Methods recommended for this multi-species eradication on Floreana Island are aerial- and ground-dispersed toxic baits (resulting in primary and secondary exposure of target populations), trapping, and hunting with and without dogs. To complement these actions, domestic cats must be sterilized and registered, euthanized, or removed from the island. Regulations must be implemented prior to the eradication to ensure that these actions can be applied to all domestic cats on the island, and that no cats can be imported to the island. Community buy-in and regulations will be required to allow access to all buildings and areas of the island, regardless of tenure. Additional recommendations are made regarding options for interisland biosecurity as well as legislation to regulate or prohibit importations of certain animals.
Factors such as a permanent community on island, tourism, and farmland/agriculture will complicate actions to eradicate rodents and cats. Although this is the case, all eradication principles can be met if the appropriate measures are taken during the planning, implementation, and confirmation phases. The technical removal of both rodents and cats is considered feasible with current eradication methods. Social, legal, and environmental acceptability has been assessed and is considered feasible within the region. Feasibility should be re-assessed periodically as results are received from processes to engage the community. A total cost of $10-12 million dollars is estimated for the planning and implementation of the recommended actions.
This document lays out a detailed description of the site and target species, recommended project approach, scope, and suggested stakeholder involvement needed to carry out a successful multispecies (mouse, rat, cat) eradication campaign on Floreana Island.

Progress in eradicating cats on Christmas Is

Algar, D., Hamilton, N., & Pink, C. (2014). Progress in eradicating cats (Felis catus) on Christmas Island to conserve biodiversity. Raffles Bulletin of Zoology. Supplement No. 30: 45–53

The impact of cats (Felis catus) on the biodiversity of Christmas Island is of significant concern to land management agencies and the broader community. In 2010, a management plan for cats, and also black rats (Rattus rattus), was commissioned that would mitigate the environmental and social impacts of these alien invasives across the island. A strategy was recommended that provided a staged approach to their management and control leading to eradication of one or both target species. For cats, Stage 1 initially involved gaining approval of revisions to the current local cat management laws that prohibited importation of new cats; this was then followed by a veterinary programme to de-sex, micro-chip and register all domestic cats. Stage 2 required removal of all non-domestic (i.e., stray/feral) cats within the residential, commercial and light industrial zones. Without implementation of Stage 2, a significant source of cats, particularly natal recruits, would be available to disperse into or reinvade territories vacated across the island. Stage 2 was required before an island-wide control programme (Stage 3) could be implemented. 

Stage 1 of the programme has been completed with 135 domestic cats currently registered. Stage 2 has led to the majority of stray/feral cats being destroyed within the residential, commercial and light industrial area. Two hundred and seventy-eight stray/feral cats were removed from this area since May 2011, primarily through cage-trapping. Two baiting programmes have been conducted around the periphery of the residential area with between 36–49 cats being removed in 2011 and a further 103–142 stray/feral cats poisoned during a more extensive programme in 2012. The combined trapping and baiting programmes have resulted in between 417–469 stray/feral cats being removed since the commencement of the plan. Continued funding is essential for a successful conclusion to the cat

eradication programme on the island.

Feral cats eradicated from Tasman Island

from http://www.parks.tas.gov.au/

Feral cats eradicated from Tasman Island

01/06/2011

Tasman Island’s sea birds are on the road to recovery following the success of a program to eradicate feral cats and restore the island’s natural values.

The Minister for Environment, Parks and Heritage, Brian Wightman, said a final check of the island last week by staff from the Department of Primary Industries, Parks, Water and Environment found no sign of feral cats and the island has been declared free from feral cats.

The program to eradicate cats from the 120 hectare island, which forms part of the Tasman National Park, began in 2008. Detailed research and planning was undertaken and an eradication plan was produced in 2009.

Tasman Island is home to Australia’s largest colony of fairy prions and it was estimated that the island’s feral cat population of about 50 was killing approximately 50,000 fairy prions and other sea birds each year.

Continue reading

Successful eradication of invasive vertebrates on Rangitoto and Motutapu Islands, NZ

Griffiths, R., Buchanan, F., Broome, K., Neilsen, J., Brown, D., & Weakley, M. (2014). Successful eradication of invasive vertebrates on Rangitoto and Motutapu Islands, New Zealand. Biological Invasions, 1-15.

An eradication program conducted on Rangitoto and Motutapu islands in New Zealand successfully removed stoats (Mustela erminea), cats (Felis catus), hedgehogs (Erinaceus europaeus occidentalis), rabbits (Oryctolagus cuniculus), mice (Mus musculus) and three species of rat (Rattus rattus, R. exulans and R. norvegicus) from an area of 3,842 ha. The project was significant because it was completed so close to Auckland, New Zealand’s largest city, but also, in contrast to many eradication projects, it targeted a suite of invasive mammals in a single operation. To achieve success and avoid conflict in the allocation of resources, target species were prioritized by likelihood of eradication success with resources allocated preferentially to species posing the greatest risk of failure and methods applied in a sequence that allowed each technique to capitalize on its predecessor. Consequences of applying this approach were increased operational efficiency, a shorter operation than planned and reduced project cost. When compared to other projects that targeted the same species but individually, we estimate the Rangitoto and Motutapu project to have cost less than 50 % of the total potential cost if each species had been removed in a discrete operation. Logistical efficiencies created by condensing several operations into one and the use of eradication and detection techniques that targeted multiple species are credited as having the greatest influence on the increased efficiencies observed.

Feral cat eradication in the presence of endemic San Nicolas Island foxes

Hanson, C. C., Jolley, W. J., Smith, G., Garcelon, D. K., Keitt, B. S., Little, A. E., & Campbell, K. J. (2014). Feral cat eradication in the presence of endemic San Nicolas Island foxes. Biological Invasions, 1-10.

Projects to eradicate invasive species from islands are a high priority for conservation. Here we describe the process used to successfully eradicate an introduced carnivore on an island where a native carnivore of similar size was also present. We primarily used padded leg-hold live trapping to capture feral cats (Felis silvestris catus). Trapped feral cats were transported off-island and housed in a permanent enclosure on the continent. We used additional methods, such as tracking dogs and spotlight hunting, to detect and remove more-difficult individuals. Project implementation caused no significant negative impacts to the endemic San Nicolas Island fox (Urocyon littoralis dickey) population. Mitigation measures included on-site veterinary resources, modified padded leg-hold live traps, conditioned trap aversion, a trap monitoring system and personnel training. To confirm eradication, we utilized camera traps and sign search data in a model to predict project success. A key part of the success of this project was the partnerships formed between NGOs, and government organizations. With support from the partnership, the use of innovative technology to improve traditional trapping methods allowed feral cats to be removed effectively in the presence of a native species occupying a similar niche. This project shows that strong partnerships, innovative methods, and use of technology can provide the conditions to eradicate invasive species when major barriers to success exist.

Cat eradication on Hermite island

Algar, D. A., Burbidge, A. A., & Angus, G. J. (2002). Cat eradication on Hermite Island, Montebello Islands, Western Australia. In Veitch, C. R., & Clout, M. N. (2002). Turning the Tide: The Eradication of Invasive Species: Proceedings of the International Conference on Eradication of Island Invasives,[University of Auckland, 19 to 23 February 2001] (No. 27). IUCN: 14-18.

Feral cats (Felis catus) and black rats (Rattus rattus) became established on the Montebello Islands, an archipelago of about 100 islands, islets and rocks off the Pilbara coast of Western Australia, during the late 19th century. They were probably introduced from pearling vessels. The largest island in the group is Hermite at 1020 ha. Three species of native mammals and two of birds became extinct well before the British used the islands for testing nuclear weapons in the 1950s. Montebello Renewal (part of the ‘Western Shield’ fauna recovery programme) aims to eradicate feral animals from, and reintroduce and introduce threatened animals to, the Montebellos. Rats occurred on almost every island and islet when eradication was attempted in 1996. In 1999 small numbers of rats were detected on Hermite and two adjacent islands and work is under way to eliminate them. Feral cats occurred on several islands at various times, but by 1995 were naturally restricted to Hermite. Feral cat eradication took place in 1999 and comprised two stages – aerial baiting and trapping. Aerial baiting utilised recently developed kangaroo meat sausage baits with flavour enhancers and the toxin 1080. About 1100 baits were dropped by hand from a helicopter. Hermite Island has two main soil types – sand and limestone. Aerial baiting primarily targeted sandy soils. Four cats, all females, remained after baiting. These were trapped using Victor ‘softcatch’^® traps set either in association with phonic and odour lures or set in narrow runways. Eradication was achieved over a six-week period. Searches for evidence of cat activity in 2000 confirmed that cats had been eradicated.

Introduced mammal eradications for nature conservation on Western Australian islands: a review

Burbidge, A. A., & Morris, K. D. (2002). Introduced mammal eradications for nature conservation on Western Australian islands: a review. In Veitch, C. R., & Clout, M. N. (2002). Turning the Tide: The Eradication of Invasive Species: Proceedings of the International Conference on Eradication of Island Invasives,[University of Auckland, 19 to 23 February 2001] (No. 27). IUCN, 64-70.

There are about 3400 islands off the Western Australian coast, many of which have high nature conservation
values. Eleven species of introduced mammals occur or occurred on 124 islands, including three domestic animals (horse, camel and sheep) that have not become feral. In addition, Aborigines introduced dingoes to at least four islands before European settlement. Six exotic mammals (red fox, feral cat, goat, rabbit, black rat and house mouse) have now been eradicated from more than 45 islands in a series of projects since the 1960s. Most effort has been directed at black rats with more than 31 islands now clear of this species. Pindone, vacuum-impregnated into oats, was used until the 1990s, when bran pellets with brodifacoum were used in the Montebello Islands. Rabbits have been eradicated using carrots soaked in sodium monofluoroacetate (1080), red foxes with dried meat baits impregnated with 1080 and cats with a combination of baiting and trapping. After a period of 20 years of ground shooting, goats were finally eradicated from Bernier Island using an experienced shooter operating from a helicopter. The house mouse has been eradicated from Barrow Island four times after introductions in food and equipment, and from Varanus and adjacent islands after introduction in food containers. Both islands are utilised by the petroleum industry. Difficulties and how they were overcome, and future eradication priorities, are discussed.