Kayangel Atoll Feasibility Report

Transcription

1 Kayangel Atoll Feasibility Report Management of Invasive Alien Species on Kayangel Atoll: Eradication of Rats, Mice and Cats This project is supported by the Australian government s Regional Natural Heritage Program through the Critical Ecosystem Partnership Fund. The Critical Ecosystem Partnership Fund is a joint initiative of the Conservation International, the Global Environment Facility, the Government of Japan, the MacArthur Foundation and the World Bank. A fundamental goal is to ensure civil society is engaged in biodiversity conservation. Tiare Holm, Palau Conservation Society Adelle Lukes Isechal, Palau Conservation Society James Millet, BirdLife Pacific Partnership Keith Broome, New Zealand Department of Conservation Andy Cox, New Zealand Department of Conservation

2 2.1 General Analysis of the problem and proposed solution as outlined in the project proposal Palau s National Report on Invasive Alien Species (2003) states the following: The Republic of Palau recognizes the seriousness of the global invasive alien species problem. Invasive alien species (IAS) are the second greatest threat to biodiversity worldwide, second only to habitat destruction. Across the globe, many invasive species have totally altered ecosystem structure and function. Many have caused enormous economic and environmental damage and some are a threat to human health. Invasions are in many cases irreversible and the problem is getting worse. In the Pacific, many experts now recognize IAS as the greatest threat to biodiversity. The majority of the world s recent extinctions have occurred on islands as a result of IAS. In Palau, concern over Invasive Alien Species (IAS) is growing because of both biodiversity conservation and resource management reasons. There is particular urgency for Palau s terrestrial environments, which have borne the brunt of the impacts of known IAS, while at the same time being some of the most understudied environments in Palau. Biodiversity is known to be high in Palau (Map 1). The country shelters the most diverse forests in Micronesia, with over 1260 known species of plants, and an estimated 25% endemism rate. There are 50 resident birds, with as many as 12 thought to be endemic. Four of Palau s bird species are considered endangered or near-threatened (Micronesian megapode (EN), Nicobar pigeon, giant white-eye, and Palau ground dove (all NT)). There are an estimated 3,000-6,000 terrestrial insects, with an estimated 26% endemism rate. There is an estimated 10% endemism rate among the nation s 47 freshwater fish, reptile, and amphibian species. There are at least 40 species of native land snails. Palau is also home to critical species such as the green and hawksbill sea turtles, the saltwater crocodile, and the Marianas flying fox. While much is known about Palau s biodiversity, there are also new discoveries made with every research attempt. There are hundreds of invasive alien species in Palau, and their full impact is not yet known; however, they are thought to have a highly detrimental effect on biodiversity. Introduced mammals, in particular, are a large concern because of their impact on endangered and other vulnerable species. For instance, the rare Palau ground dove, a gentle ground bird, has been observed being harassed by introduced rats. IAS are known to impact resource management as well. As much as 60% of Palau s rat population is thought to carry disease vectors. Water resources in particular are impacted by mosquitoes transporting Dengue Fever and rats transporting Leptospirosis and scrub typhus. (Palau experienced leptospirosis outbreaks in 1995 and 2000 and the latter resulted in two deaths.) Invasive alien animal species include: the macaque monkey (Macaca fascicularis), musk shrew, rats and mice, feral pigs, mosquitoes, fruit flies (Dorsalis bactrocera philipinensis 2

3 and D. bactrocera occipital), and rhinoceros beetle (Oryctes rhinoceros). Priority invasive alien plant species include: Chromolaena odorata, Mimosa diplotricha, Mikania micrantha, Merremia peltata, Imperata cylindrical, Spathodea campanulata, Antigonon leptopus, Clidemia hirta, Lantana camara, Leucaena leucocephola, and Wedelia trilobata. A number of eradication and control measures have been implemented to manage invasive plant species; but only a few prevention and control measures have been implemented to control invasive animal species. In Palau s National Report on Invasive Alien Species the National IAS Task Force identified a lack of on-island capacity to engage in control and eradication efforts for most IAS species in Palau. Project Location Background The four islands of Kayangel State, Kayangel, Ngeriungs, Ngerbelas, and Orak, comprise a total land area of 1.5 km 2. The sandy atoll islands are located within a 12.1 km 2 lagoon. Kayangel State is home to one of only two sandy atoll habitats in Palau (Photo 3). The islands are currently accessed only by boat, as the atoll is separated from the main Palau archipelago by 40 kilometers of lagoon and open sea. In the past, seaplanes have been used to access the islands (Map 2). Of the four islets, only one is inhabited, with a population of about 84 people. The other three islets are uninhabited, although they are used for camping, hunting, and other recreational uses. It is possible to walk from islet to islet during extremely low tides. Most of the islands are under private ownership, although some portions of the islands are owned by the state. Most of the land on the inhabited island of Kayangel is used for residential dwellings or small commercial establishments. There are small areas of agro forest and at least one known cultural site. The main island of Kayangel is served by a 100 m long by 5 m wide jetty built to foster commercial fisheries development (Photo 1). There are four species identified as a conservation priority known to reside on or utilize Kayangel Atoll: Micronesian megapode(megapodius laperouse), Marianas flying fox, and the green and hawksbill sea turtles. The population of Micronesian megapodes in Kayangel (at only 1.5 km 2 ) is thought to be the largest and most dense population in Palau, with at least 65 resident individuals counted in a survey in The 1991 Palau Forest Bird Survey estimated a population of only 497 birds for the entire rest of Palau (with an area of more than 400 km 2 ), excluding Kayangel. The islands are also home to a large population of Coconut crabs, which are harvested for local and commercial use. This project has a particular conservation concern for the endangered Micronesian Megapode. The Micronesian megapode is a ground-dwelling bird that nests in dirt mounds, which it constructs out of sand and other topsoil. The bird is listed as Endangered by the IUCN under the B1 criteria: Small and/or fragmented range coupled with a declining population. The bird is restricted to a few islands in Palau and the Commonwealth of the Northern Mariana Islands, having been extirpated from the island of Guam. Ornithologists familiar with Palau s birds have also suggested that the Palau subspecies of Megapodius laperouse be listed as a separate endemic species, although this has not been formally published. 3

4 Kayangel is known to have a number of invasive alien animal species, including: rats, mice, cats, dogs, fruit flies, and Rhinoceros beetles. Invasive plants include burr grass (Cenchrus echinatus), blue trumpet vine (Thunbergia grandiflora), and the liberal (Timonius timon). These invasive alien species are suspected of impacting biodiversity on Kayangel. For instance, local knowledge reports indicate that Kayangel used to have a full assemblage of Palau s native and endemic forest birds residing on the island (at least species); however, in the 2004 bird survey, only 3 resident species were observed. Although the reasons for the decline in bird diversity are unknown, invasive alien species are suspected of playing a role in the decline. The impact of IAS on water resources in Kayangel is also a concern, as freshwater for the island is only available from catchment tanks. Kayangel Atoll has been selected as a site for potential invasive alien species control and eradication for a number of reasons. First, the atoll is a critical habitat for the Micronesian megapode, and as such, may be listed as an Important Bird Area. Management for this species includes removal of threats, such as harassment from invasive alien species. Second, the islands provide an excellent demonstration location for invasive mammal eradication efforts in Palau. The atoll is isolated and thus the risk of reintroduction through natural means is low. Reintroduction through anthropogenic means is more easily controlled in Kayangel, relative to other islands, because the Kayangel lagoon has only one access channel and there is only one dock in the atoll. However, the atoll is not so isolated that travel to the islands is prohibitive travel from the capitol to Kayangel takes less than three hours by speedboat. The atoll system is small, and thus eradication is likely to be feasible on all four islets. Third, the human population in Kayangel is reliant on natural resources for their livelihood (including harvesting from agro forests, hunting of coconut crabs, and use of catchment water), and the impacts of invasive alien species on these resources is either not known or known to be negative (e.g. reduction in papaya harvest and contamination of water supplies). Finally, there is a consortium of national and international groups who are interested in the project and willing to work through participatory efforts to achieve both comanagement of the site, as well as capacity building for future implementation efforts in Kayangel, Babeldaob Island, and the rest of Palau. Of the alien invasive species currently known to be present in Kayangel, rats, mice and cats are considered to pose the greatest risks to biodiversity, particularly birds. Monitor lizards are also present and thought to be exhibiting invasive behavior. Their origin, whether they are native or introduced, is the subject of much debate. During the 2004 national bird surveys, rats where observed harassing juvenile ground birds Micronesian megapode and the Palau ground dove. Kayangel is home to both rare species. Reports from the community members of Kayangel reflect community observations on the noticeable significant negative impact rats have had on bird diversity and population density, as well as on drinking water quality, local agriculture and tourism. It is for these compelling reasons that rats, mice and cats have been identified as the initial target species for eradication. The presence of dogs poses similar concerns but, there has not 4

5 been enough consultation with the community to put dogs in the list of the target species for this eradication project Confirmation or establishment of a specific goal and objectives for the project that are consistent with the PII log frame matrix Goals of the project: 1. To protect and restore populations of the endangered Micronesian megapode in the Republic of Palau. 2. Restore biodiversity in Kayangel State to former natural levels. 3. To improve health and quality of life for the community of Kayangel State. 4. To build national capacity to undertake rat and mice eradication activities at all priority sites in Palau. Project Objectives: 1. Eradicate rats and mice from Kayangel Atoll (all islets) 2. Eradication of feral cats and prevention of domestic cat breeding (with the agreement of the local community 3. Increase capacity and partnerships for IAS management 4. Increase awareness and support for IAS management 5. Increase biosecurity measures to prevent reinvasion by rodents 6. Increase quarantine capacity in Kayangel State in order to prevent future introductions of non-native species to the atoll 7. Implement ongoing monitoring to determine success of project. Expected Project Outcomes: Priority outcomes include: 1. Increased population of Micronesian megapodes, leading to reduced risk to Micronesian megapodes from invasive species threats. 2. Restoration of a native assemblage of birds and other biodiversity to Kayangel atoll 3. Reduced human health hazards due to improvements in water quality 4. Creation of a team of trained, knowledgeable, local resource managers with the capacity to conduct IAS eradication, control, and prevention activities throughout Palau. Secondary outcomes include: 1. Increased public awareness of biodiversity, natural resource management, and IAS issues 2. Increased support for IAS management at the community, local government, and national government level. 3. Ongoing IAS management in other priority areas (to include Babeldaob, Koror and the Rock Islands, Peleliu, Angaur, and the Southwest Islands) 5

6 2.1.3 Confirmation of the project linkages to local, national and international priorities and commitments In addition to addressing local priorities of Kayangel, this project contributes to fulfilling three objectives under Theme 3. Biosecurity/Invasive Species and Biosafety, in the Palau National Biodiversity Strategy and Action Plan (NBSAP). These objectives include: 1. Provide a framework and capacity for ongoing prevention and management of invasive species. 2. Prevent the development of new problems with invasive species. 3. Reduce the impact of existing invasive species in Palau. In addition to this, the project also helps to fulfill targets in the CBD Programme of Work for Island Biodiversity, particularly Target 1 By 2010 at least 10% of each of the island ecological regions effectively conserved, Target 10 By 2010, pathways for major potential alien invasive species controlled, Target 11 Management plans in place for major alien species that threaten ecosystems, habitats or species. This project is also endorsed by the Palau National Invasives Species Committee (NISC) as a priority for the Republic. The project is supported by the Pacific Invasives Initiative as a demonstration project and will be one of very few such projects in the Pacific to be carried out on an inhabited island. It also presents an important learning opportunity for rodent eradication technology in tropical areas Confirmation of the potential of the project for scaling up Rats have been recognized locally as a major threat to Palau s most sensitive and sometimes most isolated eco-systems. As previously mentioned, during the 2005 National Bird Survey rats were observed harassing juvenile ground birds. These observations were mainly made in the Palau Rock Islands. Additionally, Palau has recently named it s first Important Bird Area on the small and relatively isolated island of Fanna in Sonsorol State where rats are a recent introduction (within the last ten years) and have been observed to have negative impacts on juvenile seabirds (primarily terns and boobies). One of the objectives of this project is to build national (and regional) capacity in prevention, control, and eradication of IAS. Although off-island expertise in mammal eradications will be sought throughout the project, a team of local resource managers will be managing all aspects of the project. The objective is to create a team of locally based experts who will be able to use the lessons learned from Kayangel to address eradication issues elsewhere and at future dates. Potential for scaling up the project include: 1. Building on the IAS management issues for Kayangel state by implementing further IAS eradication and control activities, including those targeted at cats and other IAS present on Kayangel. 2. Building on and further utilizing the capacity created by this project to implement rat and mice eradication activities throughout other priority sites in Palau (such as the Palau 6

7 Rock Islands and Fanna, Sonsorol Palau and Micronesia s first designated globally Important Bird Area) as well as the region Identification of risks and constraints and development of a strategy for their management Risks The recommended eradication design (sections & 2.3.2) takes account of the technical risks apparent for this project. Below are risks that relate to issues not covered in eradication design but are inherent in any project of this type. Risk one Mouse eradication is not always successful. In our experience about half of the attempted eradications of mice in the last 20 years have failed. A proportion of these due to identifiable factors such as inadequate coverage of bait, but some failed for unknown reasons. This is the subject of research at present in NZ. In the event of the successful eradication of rats but not mice we predict that mice on Kayangel will increase in numbers and it is likely that they will be introduced to the uninhabited islands as stowaways in boats. Surveillance for invading rats will also be made more difficult by the presence of mice. However achieving a rat free Kayangel will provide significant benefits to biodiversity values and human health. This leaves three options: 1. To not attempt any rodent eradication 2. To target rats only and consider the potential eradication of mice to be a bonus. 3. To target both rats and mice and accept that the risk of mouse eradication failure exists despite the mitigation measures outlined below. We recommend option 3 and the initial eradication design presented here is presented on this basis because: We consider it feasible it has been done before many times. We consider the potential benefits to be worth the cost of trying. The risk of not targeting mice explicitly is that compromises are made in the operational planning which ensure failure and may even put the achievement of rat eradication at risk. Mitigation The eradication design and operational planning is peer reviewed by independent experts. Risk two Failure to deliver on the design to a high standard will mean the eradication is likely to fail. This could be the result of problems with logistics (e.g. things not in place on time) or the project team not meeting the prescription due to poor motivation, training or supervision. It could also take the form of a collapse in local community support due to a range of issues or perceptions. Mitigation 7

8 Attention is paid to all aspects of project management including careful team selection, capacity building communication planning and involvement in all stages of the project. Logistical planning includes back up for critical equipment and details are peer reviewed by experts who understand the local conditions. Risk three The islands are reinvaded by one or more species of rodent. Dealing with newly arrived rodents on rodent free islands is extremely difficult because the ecological conditions are vastly different than those where rodents have been present for many years. Prevention is by far the most cost effective option. Mitigation A comprehensive island bio-security plan (covering quarantine, surveillance and contingency response) is written and implemented in partnership with the local community before the eradication project is complete. The eradication project needs to include sufficient funding to adequately set up the bio-security and get it functioning correctly. This is almost a project in itself, it is partly about changing some of the equipment used to transport goods but mostly it is a community project to change the behavior of island residents and visitors. Local solutions will be required which are not high cost on an ongoing basis and pragmatic from the perspective of people involved. 2.2 Environmental Assessment of the affects of the IAS Biologists and resource managers have verified the rat as a significant factor in the degradation of island ecosystems. Ground birds are particularly susceptible. The green and hawksbill turtles are also thought to be impacted. Islands are key areas for biodiversity providing critical habitat for seabirds and turtles, which use them for resting and breeding. Islands represent only 3% of the planet s surface but contain 20% of all known plant, reptile and bird species including many endemics. However 70% of species extinctions are recorded from islands, most of which were caused by invasive species. More than half of all birds on IUCN red list are threatened by introduced species. Rodents and cats are the most damaging to island ecosystems. They impact native birds through direct predation of adults, nestlings or eggs, and other species through predation, competition for food or indirectly through changes to the habitat. The four species of invasive rodents introduced to islands throughout the world are: the Brown or Norway Rat (Rattus norvegicus), the Roof or Black Rat (R. rattus), the Polynesian or Pacific Rat (R. exulans) and the House Mouse (Mus musculus). Although there are differences in dietary preferences and distributions, all are omnivorous, have high reproductive rates, and are adaptable behaviorally, which allows them to survive in a range of habitats. Norway rats are thought to have the greatest impact on burrowing seabirds. Roof rats will prey on tree-nesting birds, and Polynesian rats and house mice appear to impact a wide range of fauna. Each additional species of invading rodent 8

9 brings a new impact on the island s ecosystem. Of all island groups worldwide, less than one in five are free of invasive rodent species. Introduced rodents are the most common cause of extinction of endemic species on islands. Besides extinctions, rodents can affect the distribution and abundance of native species. Comparisons between islands infested with rats and those without rats have shown the populations of reptiles, birds, plants and invertebrates to be often much higher on rat free islands. This is backed up by monitoring of island fauna after successful rodent eradication projects. Rodents can also act as a food source for other predators, allowing those species to maintain higher populations and impacts on their native prey as a consequence. Invasive rodents also feed on plants, including the fruit, seeds and seedlings of many species. Over time this can alter the structure of plant communities sometimes degrading the quality of habitat for nesting birds. The impacts of rats are not limited to threats to biodiversity. The inhabitants of Kayangel, unlike the rest of Palau, rely solely on catchment water. This makes them particularly susceptible to vector borne diseases. Palau s experience with leptospirosis, dengue fever, and scrub typhus adds to the urgency to the efforts to control and eradicate rats. Feral cats are another significant predator of island fauna worldwide and are likely to be causing similar impacts on Kayangel Atoll. They are well known for preying on lizards, large invertebrates and nesting birds. Particularly vulnerable are ground dwelling and nesting birds such as Micronesian megapode. Dogs are not roaming wild on Kayangel but neither are they controlled or restrained. Unrestrained domestic dogs have been known to have devastating effects on ground dwelling birds, particularly kiwi and weka in New Zealand where some individual dogs became specialist predators of these species. Domestic dogs are also well known in NZ for causing nest disturbance of ground nesting shore birds such as the endangered NZ dotterel Assessment of the biodiversity benefits of the project This project aims to protect Palau s largest and most viable population of the Endangered Micronesian megapode. The Micronesian megapode is a gound-dwelling bird that nests in dirt mounds, which it constructs out of sand and other topsoil. The bird is listed as Endangered by the IUCN under the B1 criteria. They are restricted to a few islands, having been extirpated from the island of Guam. A 1991 survey estimated the number of Micronesian megapode in Palau to be 497 individuals, not including Kayangel Atoll. A 2004 survey of Kayangel estimated the population to be 65 individuals. Traditional knowledge from the Kayangel community indicates that the atoll used to maintain viable populations of many of Palau s endemic birds, such as the Micronesian Pigeon and the Palau Fruit Dove. These birds no longer live in Kayangel. There is very little development in the atoll with no significant habitat removal. Threats to terrestrial biodiversity, particularly birds, are thought to come largely from invasive alien species. 9

10 Therefore, a secondary conservation benefit to the eradication of rats and cats may very well be the restoration of a natural assemblage of endemic and other native birds. Thirdly, the four islets of the Kayangel Atoll join only one other southern atoll in making up Palau s total sandy atoll habitats and ecosystems. Atoll forests make up only 1% of Palau s total forests. Therefore, eradication of these introduced species may restore natural ecosystem functions to these rare habitats Identification of any potential negative environmental effects of the project (e.g. use of chemicals, non-target species, etc.) We recommend use of brodifacoum bait to eradicate rats, as will be discussed in section Refer to document brodifacoum pesticide information review for full coverage of what is known from New Zealand on the effects of using this chemical. Below is an extract from the Department of Conservation s risk assessment for hand broadcasting brodifacoum bait (Pestoff 20R) following the risk assessment process outlined in Crowell & Broome, 2004 Risk assessment system for pesticides used by Department of Conservation. DOC Science Internal series no Series/PDF/dsis184.pdf } Risk Assessment Summary This pesticide use is restricted to unstocked islands for eradicating rodent populations. In his context we are often prepared to withstand one-off reductions to native species populations, and the public are generally isolated from islands during poisoning. Often risks to susceptible species are managed by minimizing the exposure risk to individuals using mitigation techniques such as taking a sufficient number of individuals into captivity or by the timing of the operation (e.g. to avoid nesting period). Extremely effective supplementary technique for aerial eradications of rats. Its use as a stand-alone eradication technique is limited by the size and topography of the island. Brodifacoum, a second generation anticoagulant, is highly persistent in living tissue (especially liver), but biodegradable (to CO2 and H2O), with no toxic metabolites, in the environment. The long-term effect of sub lethal poisoning is uncertain, the persistence of brodifacoum means repeated sub lethal doses will accumulate, a situation unlikely to arise if eradication is successful and biosecurity managed. There is an antidote (Vitamin K). Mitigation required for native species likely to be at risk from the project: Megapodes. As generalist feeders, megapodes are likely to be vulnerable to both primary poisoning from eating toxic bait and secondary poisoning from eating crabs exposed to the bait. The recommended mitigation for this species is to capture as many birds as possible and hold them in captivity while the toxic bait and contaminated crabs are available (up to 2 months). Those birds unable to be captured should be monitored 10

11 throughout the operation to further determine the risk this species faces from such operations. Ground doves- May be present and may be at risk. Further work is required to determine their status on Kayangel Atoll. Attempts should be made to capture and hold ground doves (as for megapodes), especially if breeding pairs can be located. Capture and husbandry techniques require substantial further planning for this operation to maximize success. The advice of experienced ornithologists is required to ensure robust planning and execution of this part of the project. Crabs are not vulnerable to brodifacoum poisoning; they have been exposed to brodifacoum in past operations with no mortality observed despite crabs eating large quantities of bait. Mitigation measures required to eliminate poisoning risk to people People are not particularly vulnerable to brodifacoum poisoning which is why products containing are available over the counter in Palau (and most other countries) for household rat control. However this project requires specific measures to ensure no person is exposed to any poison. The primary method of risk mitigation is effective communication with all residents and visitors to ensure they understand the risks and how to keep themselves safe from exposure. A comprehensive communication plan should be written as part of project planning and the key messages regarding ensuring children, pets and domestic stock do not eat poison baits or contaminated crabs should be given to every member of the community. It is our understanding that the issue of a moratorium on collection of coconut crabs for food has already been discussed with the Kayangel community Consideration of how project benefits may be sustained after the project is completed A variety of local, national and international partners are committed to the long-term success of this project. These partners include, but are not limited to, Kayangel State Government, the Ministry of Resources and Development, the Palau Environmental Quality Protection Board, the Palau Division of Health and Sanitation, the U.S. Fish and Wildlife Service and BirdLife International. While the primary responsibility for maintaining the long term local benefits for Kayangel will rest with Kayangel State, all committed partners will continue to play a supportive role, as needed, in such areas as monitoring, prevention of reintroduction and continuing to build awareness, support and capacity. The national and regional benefits will be sustained and likely grow with the enhanced local, national and regional capacity and the continuation and scaling up of projects with similar goals and objectives. The very long-term goal is to eradicate rats and mice from 11

12 as great a portion of the Republic, and the region, as possible, as well as to continue to address all issues related to IAS in the Palau and Micronesia islands. 2.3 Technical We have evaluated the options and come up with recommendations based on the following understanding of the situation: 1. Both roof rat and Norway rat are present on all islands, except Orak, which is probably too small to support both species permanently. 2. House mice are present on main Kayangel and could be present on other islands although we expect that the smaller islands (Ngerbelas and Orak) would not support mice in the presence of such high numbers of rats. 3. The water gaps between all four islands present no natural barrier to rat migration but may do for mice. It may be possible at extremely low tide for mice to cross to Ngeriungs but the more likely route is as stowaway aboard the many small boats. The gap between Ngeriungs and Ngerbelas would be a natural barrier to mice but again the risk of stowaways is high. 4. Feral and domestic cats and domestic dogs are throughout the main Kayangel island and are likely to be impacting on bird life. The eradication of feral cats alone in this context is unlikely to provide benefits to biodiversity protection. However the removal of rodents alone is still a worthwhile objective necessary to provide any lasting protection to the uninhabited islands, which do not have dogs and may not have cats. 5. There is a sighting of feral cats on Ngerbelas (T Holm pers comm.); cat eradication on this island is both feasible and worthwhile Identification of specific techniques for addressing the IAS that are legally appropriate and suitable in a Pacific Islands context, and which maximize environmental sustainability Assessment of options and confirmation of the technical feasibility of the preferred management approach and activities (note: we considered it better to combine these two sections) Which toxins and baits should be used? Most rodent eradication campaigns in New Zealand have involved the use of one of the second-generation anticoagulants, principally brodifacoum. Floucomafen and bromodialone have also been successfully used. We are not aware of any other toxins or techniques having been successfully employed in mouse eradication operations. Given the particular challenges associated with eradicating rodents on Kayangel especially the species of rodent present, and the fact that it is inhabited, using an untried technique or an unproven toxin would add significant additional risks to any eradication operation. We discuss briefly below the various toxins, which might be considered for use in a rodent eradication operation. All but one brodifacoum, are discounted. Brief reasons 12

13 are given for this. More detailed information about these toxins, their mode of action and environmental consequences may be obtained from Department of Conservation Pesticide information reviews. First generation anticoagulants (Warfarin Diphacinone, Pindone): These pesticides have been used successfully to control rodents but they have seldom been successful at eradication projects. Diphacinone has successfully eradicated roof rats on some small islands but never mice, which require a significant dose to be lethal. First generation anticoagulants generally require rodents to feed on them multiple times on successive nights to be effective. This would be extremely difficult to achieve without using bait stations to deliver the bait due to the presence of land crabs taking bait. Floucomafen and Bromodialone: The effectiveness of brodifacoum in rodent control and eradication operations is better known than for fluocomafen or bromodialone. We cannot see any advantage in using either of these otherwise apparently suitable alternatives. The relative lack of information of the environmental effects of bromodialone and floucomafen is a further consideration (sodium monofluoroacetate) and Cholecalciferol: As with other acute (fast acting) toxins bait shyness is more likely, making it unsuitable for rodent eradications. Brodifacoum Advantages - Proven successful in many eradication campaigns - Well-known effects means clearer idea of the mitigation actions necessary - Antidote available for pets, humans, livestock Disadvantages Ssignificant non-target risks to wildlife and pets, most of which can be mitigated, but some may not. We conclude that the only toxins currently available, which would provide a realistic prospect of success, are the second-generation anticoagulants. We believe that brodifacoum clearly stands out as the preferred choice for eradicating both rats and mice. Considerable research has been conducted into brodifacoum, and its successful use to achieve eradication objectives has been demonstrated many times globally. The major drawback with this toxin is the potential for unacceptable non-target effects. However, as a result of previous research and experience in eradication projects, these effects can often be predicted. With such information, mitigation can, in most situations, be undertaken where necessary to reduce risks. The high-risk period during eradications is a relatively short period -a matter of a few weeks, until bait decomposition and animal 13

14 tissue containing toxin breaks down. The toxin is still potentially biologically available within the environment for longer than this, but it biodegrades over time. Choosing bait which is attractive to all rodents and which will remain palatable long enough for all rodents to consume a lethal dose of toxin is a critical element in successful rodent eradications. The bait in which the toxin is held must be extremely palatable to rodents, and must be in a form suited to the method of distribution and presentation. There are several commercially available bait to choose from. Compressed grain pelleted baits have proven to be particularly palatable to rodents in eradication operations worldwide. The advantage is that an adequate dose of rodenticide is delivered compared with loose grain, or waxy blocks, which may not result in rodents receiving a lethal dose of toxin. The form of the bait can also affect its attractiveness to rodents. Some pellets, for example, break down quite quickly in rain, whereas waxy blocks remain palatable longer but are known to be less palatable to rodents. Some commercially available bait include the compound bitrex which is intended to make them taste bitter, and therefore less attractive to non-targets including people. There are indications that bitrex may also induce bait aversion in rodents, and may have contributed to the failure of at least one eradication operation targeting mice. Baits containing bitrex are now not used in rodent eradication operations undertaken by the Department of Conservation in New Zealand. We recommend using the proven brodifacoum pellet bait produced by Animal Control Products. Alternatives could be considered if they met the following criteria: Bait has proven palatability to all rodent species targeted Manufacturer has a proven track record of quality control at all steps in the manufacturing process. Bait has proven storage life and has been used in conditions likely to be encountered in Palau. There is sufficient information about palatability to non-target species to enable those species at risk to be predicted and the risks managed to acceptable levels. Options for bait distribution: Kayangel (main island) 112ha. Target species: Norway rat, roof rat; house mouse, feral cat. Other bait consumers (which will compete strongly with rodents for bait): Land crabs, Hermit crabs, Coconut crabs, Wild chickens Non-target species: Domestic pigs, chickens, cats, dogs. Low numbers of megapodes, monitor lizards. Possible options 14

15 1. Helicopter broadcast poison bait 2. Hand broadcast poison bait 3. Poison baiting using bait stations. 1. Helicopter broadcast: Least risk of failure to eradicate No helicopter in Palau Logistics difficult to bring the required equipment and expertise together (including back-up to allow for breakdowns and illness). Does not develop ground baiting capability Requires enough bait to overcome competition for bait by other consumers. 2. Hand broadcast More risk of failure than helicopter but less than bait station Requires enough bait to overcome competition for bait by other consumers. Logistics manageable the terrain is easy and the vegetation will require some line cutting but is largely manageable with a light jungle knife Develops capability that can transfer to other places Uses more bait but takes less time than bait stations No cost of bait stations Some cats will take rat baits and die In theory non-target species are more exposed to the pesticide when broadcast compared with contained in bait stations. However the quantity of bait required for this operation and the other bait consumers taking it up mean that the pesticide will be readily available to non-target species no matter what method is used. Hence the use of bait stations will not obviate the need for non-target mitigation measures. 3. Bait stations To successfully target mice would require a 20m x 20m grid & risk of failure would remain stations required to be installed and serviced Logistics very difficult with so many stations to install and then visit several times to re-bait there is a high chance of some being misplaced or missed without a large supervision effort. Competition between rodent species an issue best case scenario an extended baiting period required to achieve eradication of all species; worst case scenario some animals do not enter any station and thus survive causing the project to fail. Develops capability that can transfer to other places Cats will not take any rat baits from stations. Bait stations may reduce the amount of bait taken by other bait consumers if the design of them can successfully exclude crabs without deterring rodents. 15

16 Summary and Recommendations Helicopter broadcast will not be a strategically useful technique for a demonstration project in Palau as it will have limited application elsewhere. It will also be difficult to arrange to bring together a suitable helicopter, a pilot skilled in aerial bait spreading, and the required sowing and navigational guidance equipment necessary to do the project successfully. However, this method is not discounted and will need to be further explored. Bait station delivery of poison is considered feasible at this stage but the risk of failure to eradicate mice especially is a significant consideration. This option is not recommended because of this risk and because the logistics of implementing the required design on this scale would be very difficult and expensive. Hand broadcasting of bait is the preferred option as it has a greater chance of success because the logistics are more manageable and the issue of inter-specific competition among rodent species is overcome. Countering this is a risk of bait being consumed by other species (e.g. crabs) before all rodents can access it. This aspect requires further work (see 2.3.3). A combination of hand broadcasting and bait stations is a possible outcome of the final planning process - which requires more in-depth consideration of exactly how each island is to be treated than is appropriate for a feasibility study report. Where are the risk areas to the eradication being successful? Most risk areas are on the main island and associated with the village. The taro gardens are in water year round and are quite large (Photo 2). The buildings and surrounding refuse management present an ongoing supply of alternative food to rodent. Ngeriungs also has a wetland. The coastal margin has high densities of hermit crabs, which may take bait before rodents can access it. Ngeriungs 34ha. + Ngerebelas 8.6ha + Orak 1.7ha Target species: Norway rat, roof rat, possibly mice, possibly cats. Other bait consumers: Land crabs, Hermit crabs, Coconut crabs, Non-target species: About megapodes, ground dove, monitor lizards Possible options 1. Helicopter baiting poison bait 2. Hand broadcast poison bait 3. Poison baiting using bait stations. 1. Helicopter broadcast Least risk of failure to eradicate No helicopter in Palau 16

17 Logistics difficult to bring the required equipment and expertise together (including back-up to allow for breakdowns and illness). Does not develop ground baiting capability Requires enough bait to overcome competition for bait by other consumers. 2. Hand broadcast Less risk of failure than bait station Requires enough bait to overcome other bait consumers. Logistics manageable (if terrain & vegetation ok) Develops capability that can transfer to other places Uses more bait but takes less time than bait stations No cost of bait stations 3. Bait stations Logistics manageable Competition between rodent species an issue best case scenario an extended baiting period required to achieve eradication of all species; worst case scenario some animals do not enter any station and thus survive causing the project to fail. Develops capability that can transfer to other places Manages most risk to megapodes from primary poisoning. Manages risk of crab take making bait unavailable to rats Summary and Recommendations Helicopter broadcast will not be a strategically useful technique for a demonstration project in Palau as it will have limited application elsewhere. It will also be difficult to arrange to bring together a suitable helicopter, a pilot skilled in aerial bait spreading, and the required sowing and navigational guidance equipment necessary to do the project successfully. However, this method is not discounted and will need to be further explored. Bait station delivery of poison is considered feasible at this stage but the risk of failure to eradicate both species of rat is a consideration. This option is not recommended because of this risk. Hand broadcasting of bait is the preferred option as it has a greater chance of success because the issue of inter-specific competition among rodent species is overcome. Countering this is a risk of bait being consumed by other species (e.g. crabs) before all rodents can access it and the risk to megapodes, especially on Ngeriungs. Hand broadcasting bait will require protection of megapodes, by capturing and holding in captivity. Those that are not caught will be exposed to the bait, which will allow the question of their vulnerability to this technique to be answered for future projects where megapodes are present. We recommend a proportion of the megapodes be taken into captivity for the duration of the poisoning whatever option is chosen because: 17

18 o This will act as a safeguard against secondary poisoning caused by megapodes eating crabs containing poison. o It will develop the capability for managing megapodes in captivity, which can be applied to subsequent projects in Palau. o Capture and release will allow these birds to be marked which will facilitate monitoring of their fate upon release into a rodent free habitat. Preliminary design of eradication techniques These techniques take the feasible options identified above and develop them into a preliminary plan for the purpose of further exploring the logistics and to provide a basis for costing the project. It must be noted that considerable further work is needed to produce a comprehensive operational plan, which takes account of all the issues identified in this report. Hand broadcasting 1. Cut/mark parallel transects 20m apart (depending on vegetation) 2. Two applications of 12 kg/ha (to overwhelm other bait consumers on each application) 3. Second application a minimum of 14 days after the first 4. Extra bait applied on coast (if concerned about higher crab take here) 5. All islands done this way will require a total of 4600kg of poison bait. This allows a 20% contingency. Our recommendation would be to order 5 tonne from the factory and this would fit in one shipping container. 6. Timing considerations avoid tern breeding season, times where extra food is available to rats in gardens, wet season. If possible plan for a period where crab activity is lower (possibly end of dry season April/May). 7. Once transects are marked poison laying would take a maximum of 1 month to complete. Poison could be expected to be active on the island for a maximum of 2 more months after this although this would require monitoring during the project to be sure. 8. Other recommendations to increase the chance of success- must be in place well ahead of poisoning: o Good refuse management to manage rodent habitat available and alternative food sources for rodents. o Good rodent proof food storage for all households. o Take domestic stock into captivity and manage their food and waste effectively to minimize alternative food source for rodents. The best (but not the only) option is to remove domestic stock from the island until poisoning is complete. o Communication strategy to manage expectations 18

19 o Children explain dangers; retain the option to have children off the island while poison is there (for peace of mind). Bait stations 1. Establish a 40 x 40m grid for rats and feed poison for 1 month. 2. Fill in grid with extra lines to create a 20m x 20m grid and feed until bait take by rodents is zero. 3. Switch to block bait (suggest Pestoff Rodent block but this will need testing) for two more months. This change in bait will offer something new to any remaining rodents and should last longer in the stations thereby needing less frequent checking. 4. A total of 3200 stations required for main Kayangel Island. Design will need testing to ensure crabs cannot access significantly and all rodent target species can. 5. assuming 10kg/ha bait consumed (taken from a bait station project in French Polynesia Rangiora??)- then approximately 2000kg of pellet bait required plus 10,000 block baits. 6. Other recommendations to increase the chance of success- must be in place well ahead of poisoning: o Good refuse management to manage rodent habitat available and alternative food sources for rodents. o Good rodent proof food storage for all households. o Take domestic stock into captivity and manage their food and waste effectively to minimize alternative food source for rodents. The best (but not the only) option is to remove domestic stock from the island until poisoning is complete. o Communication strategy to manage expectations o Children explain dangers; retain the option to have children off the island while poison is there (for peace of mind). Cat eradication 1. Many (most?) cats will die as a result of rat poisoning days after last rat bait application lay 1080 cat bait station line around perimeter of island and down center road. 3. Stations 200m apart- about 50 stations, designed to deter monitor lizards and crabs- needs testing 4. Targeted leg hold trapping by very skilled trapper to follow up 5. Monitor lizards are probably at risk to both techniques Identification of research needs and further trials The option of helicopter baiting need to be further explored. 19

20 The choice of bait type requires further work to establish the best option for palatability to target species and ability to withstand the Palauan environmental conditions. Bait estimates need to be confirmed. The operational plan will need to establish a robust design for treating the risk areas (taro gardens, village, coastal areas). These areas will require careful mapping. The sacred area requires mapping to determine the exact size and boundaries and what restrictions apply that may compromise the eradication. Bait sowing rates need further consideration in light of other successful operations undertaken with similar rat and crab densities. Research into the home ranges of the rodent species present in tropical environments would be beneficial but not essential. If the bait station delivery option was taken, such studies would be necessary for mice at least. Resolve the status and future management of monitor lizards. There appears to be confusion over whether the animals are a natural part of the Kayangel ecosystem or not and perceptions of their impacts on (other?) native species may not be valid in all cases. We recommend further specialist advice be sought and where necessary trials be conducted on Kayangel involving local people. Cat baiting techniques need further development and refinement to ensure the non-target risks can be adequately managed whilst remaining effective against cats. A rodent survey to determine the species on each island was considered but not thought to be worthwhile for the following reasons: i. Reports of the species present on the main island appear convincing and reliable. DEH officers regularly visit the island and are very experienced in identifying rodent species. ii. The recommended eradication design assumes the worst and plans for mice to be present on all islands. A survey would not change this recommendation. It merely allows us to categorically say which species were present before and therefore which species were eradicated from each island. iii. The high densities of rats on the uninhabited islands would make it impractical to survey for mice (which usually requires rats to be locally trapped to low numbers before mice can be detected) Identification of the skills needed to implement the project, skill gaps and any necessary training Skills required to implement this project: A project manager who is dedicated exclusively to this project. This person will require 20