Analysis of the problem

Gough Island, part of the Tristan da Cunha group, is one of the UKOT’s most important sites for biodiversity, as recognised by the island’s status as a natural World Heritage Site (one of two in the UK OT’s), Site for Zero Extinction (one of seven in the UK OT’s) and an Endemic Bird Area. Supporting two endemic landbird species and 20 species of breeding seabird totalling tens-of-millions of individuals, Gough is often described as one of the world’s most important seabird islands.

Invasive alien species are the main threat to the biodiversity of the UKOT’s and the key threat to the biodiversity of Gough Island is the presence of invasive House Mice (Mus musculus) and the invasive weed Procumbent Pearlwort (Sagina procumbens). Rats, cats and mustelids have long been recognised as among the world’s worst invasive species, however the impact of invasive House Mice has until recently been perceived as relatively minor. House Mice were first recognised as a larger conservation problem in 2000/01, when it was discovered that the species was a major predator of winter-breeding seabirds on Gough Island.

Follow up research has established that mice are responsible for unsustainable breeding failures of the threatened and near-endemic Tristan Albatross and Atlantic Petrel in all 4 years studied, accounting for the mortality of upwards of 400,000 chicks each season. Population modelling indicates that both species are likely to be in long-term population decline as a direct consequence of mouse predation. Recent mouse-related declines in the small population of the endemic Gough Bunting has led the RSPB to recommend to BirdLife International (the official body that reports to the IUCN’s Red List of threatened species) that the conservation status of Tristan Albatrosses, Atlantic Petrels and Gough Buntings be upgraded to Critically Endangered: the highest threat category available. Other winter-breeding seabirds including Great-winged Petrels and the Near Threatened Grey Petrel are also likely to be heavily impacted by mice.

The wider impact of mice on Gough Island’s native and endemic flora and invertebrate fauna is likely to be large and negative. The invasive plant Sagina procumbens is a native of northern Europe which has been very successful in colonising and spreading to sub-Antarctic islands throughout the world. Sagina has colonised both Marion and Prince Edward Island (South Africa) and Tristan da Cunha. On Marion the spread of Sagina has caused a major change in the floral composition of the island’s bogs and feldmark vegetation: Sagina now dominates these areas forming thick mats to the exclusion of other native plants. The long-term impact of Sagina on Marion and Prince Edward are unknown, however it is likely there will be major changes in invertebrate communities and nutrient cycling (especially peat formation).

Project context

During recent years, technology and know-how for the eradication of invasive alien rodents has been developed. This has resulted in spectacular biodiversity recovery and ecosystem restoration at sites such as Campbell and Raoul Islands (both New Zealand) and many others. Consequently, island rodent eradications have become a major tool in attempts to reduce the rate of biodiversity loss worldwide. The discovery of the impact of House Mice on Gough Island has changed global perceptions and priorities for eradications of invasive species. Previously, many eradication operations have aimed to get rid of rats and cats, whilst (unintentionally) leaving house mice as the sole remaining non-native species. With the discovery of their impact on Gough Island, eradication operations are now researching and planning for the eradication of mice.

Among the UK OT’s, the major sites on which rodents are thought to have devastated globally important biodiversity, and where eradication is a plausible option (due to lack of a large human population) are Tristan da Cunha, Gough, and Henderson islands. The “Management Plan for the Gough Island Wildlife Reserve“ has as a long term goal, “the removal of mice from Gough Island”, and the workshop report “Assessing Management Options for the introduced rodents of Tristan da Cunha” (funded under TDC203) states that the “biodiversity gains from a mouse eradication on Gough would be immense”. The RSPB research report “A review of the impacts of introduced rodents on the islands of Tristan and Gough” (funded under TDC203) concludes that “If house mice impacts are removed from Gough then a recovery of affected bird populations is expected, leading to an improved conservation status, as well as maintenance of plant and invertebrate communities”.

The role and potential impact of invasive plant species on islands has long been recognised. However, it is only in recent years that conservationists have begun the control and attempted eradication of these plants, as well as greatly increasing efforts to prevent the introduction of further species. In the Tristan da Cunha group and Gough Island projects supported by RSPB, UCT and OTEP projects TDC201 and TDC403 have started to eradicate and control invasive plants. Control work on Inaccessible and Nightingale islands (TdC) in 2004 and 2007 (supported by TDC002 and TDC403) has been successful in removing invasive New Zealand Flax from a large area of tussock and coastal cliffs, preventing the spread of this species in to upland areas where it would become out of control. The invasive grass Arrhenatherum elatius was successfully eradicated from around the weather base at Gough Island during 2005/06. Control operations are underway on Tristan to remove loganberry from Sandy Point area and prevent the spread of this species in to upland areas. Support from the RSPB managed South Atlantic Invasive Species Project is helping Tristan to increase quarantine facilities to prevent the introduction and spread of further invasive plant species.

Complementary initiatives, and other relevant programmes/projects

RSPB is the UK partner of BirdLife International and is in contact with BirdLife partners and conservation organisations worldwide in connection with island eradication operations. Very ambitious initiatives to eradicate mice from sub-Antarctic/cool temperate islands are being developed by government bodies of South Africa, Australia and New Zealand.

This research compliments the RSPB managed South Atlantic Invasive Species Project that aims to build capacity with the South Atlantic OT’s to undertake and manage the risks posed by invasive species, including both invasive rodents and invasive plants.

Co-ordination with other agencies working in the country

By virtue of the current and past OTEP projects (TDC 201, 203, 302 & 403), it has been possible to keep a dialogue open with the Tristan da Cunha Agriculture and Natural Resource Department and Tristan’s Island Council and Chief Islander(s). Close collaboration has also existed with the University of Cape Town through coordinated work programmes on Gough Island and Tristan’s biodiversity. The rodent feasibility assessment for Tristan da Cunha and Gough has involved working with rodent eradication experts from New Zealand (the country that leads the world in successful rodent operations), putting this project in contact with leading experts and organisations involved with eradication of rodents. These stakeholders have been able to comment on successive drafts of the feasibility study, and thus on the work programme of this proposal.

How the new activities build on the previous ones

This project is a direct follow-on from TDC203 and TDC403. The proposal has emerged from the Gough Feasibility Study for mouse eradication, which highlighted key areas of uncertainty, which need to be resolved before the Operational Plan can be finalised and fundraising begins. These key questions are the determining bait preference and efficacy of poisons, determining the susceptibility of mice in caves/lava tubes, and undertaking a bait acceptance trial. Actions described within this project are not required for the eradication of rodents on Tristan da Cunha as there are less areas of uncertainty involved in rat eradication operations, and capacity and training to undertake such an operation on Tristan is being built through the South Atlantic Invasive Species project. The control of Sagina on Gough Island continues the work of TCD403 and will utilise a third year of funds available through this current OTEP project. Monitoring and ecological studies of birds on Gough builds on research and monitoring work established in 2000 and earlier, and is crucial for determining population trends and the extent of the threat faced by these species.

• Report identifying the optimum bait and poison to target all mice during the winter-period when an eradication operation would occur.

• Report describing the behaviour of mice that are partly or fully based within caves and underground lava-tubes and the potential susceptibility of these mice to an aerial baiting operation.

• Report on the success of a medium-scale (non-poison) bait application at targeting all individual mice within a defined study area.

• Peer-reviewed scientific paper(s) summarising outputs 1-3 to report to the global eradication community and potential funders, and to be used as key inputs to a finalised Operational Plan for mouse eradication on Gough Island.

• Report on the ongoing efforts to contain and eradicate Sagina from Gough Island, summarising efforts to date (from 1999 to 2009), success of these actions and best-practise for the future.

• Report and peer-reviewed scientific paper summarising long-term monitoring of bird populations on Gough Island from 2000/01 to 2008/09, and the population trends and demographic parameters of Globally Threatened birds.

1. Project managed in an effective and participatory manner.

   Project communicates effectively with stakeholders and relevant experts.

   Existing email contact continues to be used as a means of regularly involving stakeholders.

   Regular email contact maintained with rodent eradication specialists, including Island Eradication Advisory Group, the New Zealand Department of Conservation (who have offered technical support for the eradication), University of Cape Town and rodent and plant eradication consultants for TDC203 and TDC403, to ensure best practice, integration of data and continuation of Sagina eradication.

   RSPB website and Aliens newsletter used to publicise the project and inform wider stakeholders.

   The project will fully engage Tristan and the Tristan Agriculture and Natural Resource Department in the final steps required for preparing for an eradication on Gough, providing key areas of knowledge for an attempt on Tristan itself.

2. Logistical arrangements made for safe and cost-effective deployment of fieldworkers and research plan on Gough Island.

   Berths secured for personnel and equipment to Gough during 2008 and 2009 and equipment procured for bait trials, mouse research, and Sagina eradication.

   Fieldwork team with required set of skills (camp management, rope-access qualifications for cliff work on Sagina, first aid, rodent control, bird research and monitoring, experience of Gough/Tristan and/or sub-Antarctic islands) recruited.

   Necessary training given to fieldworkers prior to departure, especially rope-access training if required (preferably an Industrial Rope Access Training Award level 1 or above).

   Support arranged through the South African National Antarctic Programme and operating helicopter company during the relief voyages utilising the S.A. Agulhas supply ship and its logistical capacities.

3. Fieldwork team deployed on Gough Island for 13 months from September 2008 to October 2009.

   Two experienced fieldworkers to be on Gough from September 2008 to October 2009, joined by fieldworkers from Tristan da Cunha and RSPB/UCT personnel during September 2008 and September 2009 (when the South African supply vessel the SA Agulhas visits Gough).

4. Mice bait preference trails to determine the optimum bait-size, composition and efficacy of poisons.

   Bait pellets of varying size and composition will be sourced in collaboration with rodent bait manufacturers from New Zealand. Bait preference trials will be undertaken using choice-tests in the lab, depletion rate trials in the field, and studies of mice behaviour to determine the composition and size that is most preferred during the winter months (when an eradication operation would take place) and that is most likely to target all individuals. Poison efficacy trials will be undertaken in the laboratory to determine the speed and effectiveness of second-generation anti-coagulent poisons at killing Gough Island’s mice, and if there is any gender or strain specific resistance to brodifacoum (the most proven poison for rodent eradications).

5. Experiment to determine the susceptibility of cave and lava-tube dwelling mice to an aerial eradication.

   Underground caves and lava-tubes are common on Gough Island and contain breeding petrels, as well as mice. Consequently if some mice remain wholly in caves during an eradication operation they may not be exposed to poison baits. The experiment will be undertaken in accessible caves and lava-tubes on Gough (at least 7 such systems have been identified and mapped). Mice within caves will be live-trapped over 4 consecutive nights and marked with individually numbered ear-tags. On day 5, rhodamine-dyed non-toxic bait that has the same formulation as normal toxic bait will be hand-broadcast at densities equivalent to 12 kg/ha within a 100 m radius of the cave’s entrance(s). The baiting density and radius is based upon the baiting protocol used in successful rodent eradications and the maximum distance moved by radio-tagged mice on Gough. Mice will be kill-trapped within each study cave for 3 consecutive nights after bait distribution. All trapped mice will be examined for the presence of fluorescent rhodamine bait marker within their intestinal tract, and whiskers will be removed and tested for rhodamine. The results will be analysed to determine the proportion of cave-inhabiting mice taking bait.

6. Undertake a medium-scale bait acceptance trial.

   More than 500 mice within a lowland study area of 400 x 400m will be live-trapped during July and August and marked with individually numbered ear-tags. Repeat live-trapping and mark-recapture analysis will be used to determine the population density of mice and the proportion of marked individuals within the population. During the winter bait will be hand broadcast at a baiting density of >12 kg/ha. To mimic a double baiting operation, two bait applications will be made: the first with rhodamine dyed non-toxic bait, and the second 7 days later with pyridine dyed non-toxic bait. Two days after the second bait drop the core area of the study (100 x 100m) will be extensively kill-trapped to capture as many mice as possible. The identify (from ear-tags) of all trapped mice will be recorded and all mice will be examined for fluorescent rhodamine and pyridine bait marker within their intestinal tract, and whiskers will be removed and tested for presence of markers. The results will be analysed to determine if the application successfully targeted 100% of marked mice (by only examining resident marked mice we can exclude the confounding effect of dye-free mice that have immigrated in to the study area after the bait application). Additional (live) trapping of the endemic Gough Moorhen will be undertaken after the first bait drop to examine them for the presence of rhodamine and assess the risk to these species of poisoning during a poison bait-drop.

7. Continue containment and eradication of Sagina.

   The introduced plant Sagina procumbens is restricted to 200m of coastal cliffs close to the weather base. Control operations since 1999 have been successful in restricting the spread of the Sagina, however some years of low effort and a lack of necessary expertise to safely access vertical cliffs has prevented its eradication. Efforts have been greatly increased since September 2006, with 2-3 teams undertaking control during spring, summer and winter periods. This work has prevented Sagina from flowering in all known areas for the last 2 years, leading to a great reduction in the plant’s seedbank. The infected area of Sagina has also decreased in area in the last 2 years: showing the success of the intensive control programme. The project will continue this intensive control, spending 20-25 field days in the spring, summer and winter periods. The team will access cliffs using specialised industrial rope-access techniques to safely reach cliff areas. All visible plants and soil will be removed, and remaining areas will be sprayed with herbicides. Detailed mapping of all affected areas will monitor the containment and control of Sagina in comparison with previous years. Searches will also be made in new areas beyond the current affected area. Germination experiments will be used to determine the number of seeds remaining in all treated areas and to monitor progress against September 2006, when germination experiments were last undertaken.

8. Monitoring bird populations on Gough Island.

   Methods for the long-term monitoring of Gough Island bird populations were established in 2000-2001. This study, along with a review of earlier counts, enabled new population estimates to be provided for many species, as well as a reassessment of the trends and conservation status of six of Gough’s Globally Threatened species. Repeated monitoring of bird populations has been undertaken in 2000/01, 2003/04 and 2005/06. A fourth year of monitoring will provide sufficient data to re-evaluate the population size and trends of key bird populations. The survey team will undertake monitoring throughout the year following the protocols established in the 2000/01 monitoring manual.

9. Studies of Tristan Albatrosses and Gough Buntings.

   The impact of mice on the Critically Endangered Tristan Albatross is driving declines in this species, however the full extent of the threat is unknown without better knowledge of the species’ demography. When successful in rearing a chick Tristan Albatrosses breed every second year, however on Gough most breeding attempts result in failure due to mice. Because of this, it is unknown if Tristan Albatrosses are returning every second year to breed, or because of the failure are attempting to breed annually. Survey teams in 2007 and 2008 have recorded the identity of all breeding birds in two study areas and know the success or failure of all breeding attempts. A third year of study in 2009 will crucially allow the estimation of re-breeding rate and the also the overall size of the breeding population. Both of these factors are very important for assessing the impact of mice and longline mortality on the population. The survey team will record the identity and band all breeding Tristan albatrosses in two areas during the egg-laying and incubation period (Jan-March). A total island count will be undertaken at the same time. In September 2009 a total island count will determine breeding success for the whole population. Recent assessment on numbers of Gough Buntings has caused this species to be uplisted as Critically Endangered due to the impact of mice predation. The team will monitor the size of the population and causes of breeding failure in different areas of Gough Island that are likely to be subject to varying rates of mouse predation. This work will determine the full impact of mice on this species, and to assess how rapid decline rates are for the small population of buntings (just 500 pairs), and if urgent remedial conservation actions are required.

10. Analysis and reporting.

    Reports on activities 4 to 9 produced by fieldworkers and project manager, and circulated to stakeholders before formal publication as RSPB Research Reports, peer-reviewed scientific papers, and posted on RSPB and Tristan da Cunha websites. Reports on activities 4-6 will subsequently be used by an international eradication expert to produce a full operational plan for the eradication of mice from Gough Island. Reports on activity 7 will allow a reassessment of the Sagina control programme and determine the long-term plan for eradicating this weed. Reports on 8 & 9 will determine population trends and the extent of the threat to Gough bird species, and will be used for evaluating the IUCN/BirdLife Threatened status of these species.

• Tristan da Cunha government and community:

  The Conservation Officer and Head of the Agriculture and Natural Resource Department of Tristan da Cunha have been consulted about the project proposal and support its submission. They have also been partners of TDC203, including the Chief Islander participating in the Cape Town workshop.

• The Tristan Biodiversity Advisory Group:

  This Committee is responsible for implementing the Gough Island Management Plan and co-ordinating conservation management of the island. The Committee has been consulted about the project proposal.

• Other biodiversity conservation agencies/people with an interest in the island & its species:

  We have also discussed the project with various New Zealand eradication experts and bait manufacturers.

These stakeholders already form the basis for a communication and consultation group for TDC203, and this would be continued if the proposed project is funded.

Risk 2: Failure to acquire suitable expertise and equipment for fieldwork.
Probability: Low
Impact: High
Management: Bait manufacturers have already been contacted and are aware of the potential work programme and the project’s requirements. Rope access training and necessary climbing equipment will be undertaken and ordered well in advance of the project.

Risk 3: Effective logistical support on the island is not available.
Probability: Low because the project will fall under the SANAP programme where support will be given.
Impact: High
Management: All potential steps will be taken in advance to ensure SANAP gives sufficient priority to this work to ensure it will occur during the key research periods, with necessary helicopter and small boat support during takeover periods, and support of the team throughout the year.

• Removing House Mice from Gough Island and preventing the spread and eradicating Sagina are the two major activities required to restore this World Heritage Site to an almost pristine state, and meet key requirements under the Convention on Biological Diversity (CBD) and Agreement on Conservation of Albatrosses and Petrels (ACAP)

• Eradicating mice would prevent the extinction of several globally important seabird populations and the endemic Gough Bunting, and would result in the ultimate recovery of these species as well as recoveries in endemic and native flora and invertebrate species.

• It would be by far the major rodent eradication to take place outside New Zealand to date, and would signal the UK and the OTs’ intentions to undertake ambitious, high-profile restorations of their globally important islands.

• An eradication of House Mice from an island the size of Gough will change the direction of global eradication operations over the next decade as the conservation impact and benefits of removing mice has only recently been fully recognised.

• Controlling and eradicating Sagina will protect the unique upland vegetation and invertebrate communities of Gough Island from being overrun by this invasive plant, as has occurred at many other sub-Antarctic islands.

• Monitoring of population trends and demographic parameters of Gough Island’s bird populations to assess status and trends and provide a baseline for future mouse eradication.

All of the activities would make a major contribution to the UK meeting its obligations under the CBD, ACAP and World Heritage Conventions.

Multilateral Environmental Programme

World Heritage Convention

Gough Island is a natural World Heritage Site, one of two such in the UK OT’s. The other, Henderson, also has as its major conservation issue the presence of introduced rodents. As part of the World Heritage inscription, a Management Plan must be adopted.

The OTEP funded feasibility study reports that:

The Gough Island World Heritage Site is inscribed because it is “one of the least-disrupted island and marine ecosystems in the cool temperate zone. The spectacular cliffs, towering above the ocean, are home to one of the world's largest colonies of sea birds. The island is also home to two endemic species of land birds, the gallinule and the Gough rowettie, as well as to 12 endemic species of plants.”

Article 5 of the Convention Concerning the Protection of the World Cultural and Natural Heritage notes that:

“To ensure that effective and active measures are taken for the protection, conservation and presentation of the cultural and natural heritage situated on its territory, each State Party to this Convention shall endeavor, in so far as possible, and as appropriate for each country: to take the appropriate legal, scientific, technical, administrative and financial measures necessary for the identification, protection, conservation, presentation and rehabilitation of this heritage;”

Convention on Biological Diversity

Island biodiversity is one of seven ‘thematic programmes’. A mouse eradication on Gough Island would reverse the loss of biodiversity at this site, and thus assist with meeting the 2010 biodiversity target.

In particular, Article 8. In-situ Conservation. “Each Contracting Party shall, as far as possible and as appropriate:…

(f) Rehabilitate and restore degraded ecosystems and promote the recovery of threatened species, inter alia, through the development and implementation of plans or other management strategies;

(h) Prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species;”

Invasive Alien Species have been recognised as a major “cross-cutting issue” by the Conference of Parties.

Convention on Migratory Species: Agreement on Conservation of Albatrosses and Petrels (ACAP)

ACAP is highly relevant to Tristan, because the Territory holds significant populations of five longline-affected seabird species, of which three are endemic.

Under Article III (general conservation measures) of ACAP, signatories are required to:

1. In furtherance of their obligation to take measures to achieve and maintain a favorable conservation status for albatrosses and petrels, the Parties, having regard to Article XIII, shall:

a) conserve and, where feasible and appropriate, restore those habitats which are of importance to albatrosses and petrels;

b) eliminate or control non-native species detrimental to albatrosses and petrels;

c) develop and implement measures to prevent, remove, minimize or mitigate the adverse effects of activities that may influence the conservation status of albatrosses and petrels;

The Action Plan that forms Annex 2 of ACAP notes the following.

1.4 Non-native Taxa

1.4.2 The Parties shall take measures to the extent feasible to control and, where possible, eradicate non-native taxa of animals or plants, or hybrids thereof, that are, or may be, detrimental to populations of albatrosses or petrels. Such measures should satisfy to the extent feasible, humane and environmental considerations

2.2 Land-based conservation

2.2.1 Where feasible, the Parties shall give protection to the breeding sites of albatrosses and petrels, using existing mechanisms where available. For all such protected areas, the Parties shall endeavor to develop and implement management plans and take other actions which maintain and enhance the conservation status of the species, including inter alia the prevention of habitat degradation, the reduction of disturbance to habitats and the minimisation or elimination of damage by introduced non-native animals, plants, hybrids or disease-causing organisms.

Environment Charter

The project will assist Tristan da Cunha in meeting requirements under the Environment Charter.

There is no formally documented strategy for the implementation of the Environment Charter (although a Biodiversity Action Plan has being prepared by Tristan Department of Natural Resources). However, this project contributes to the meeting of several of the UK government and Tristan da Cunha commitments under the charter.

Gough Island, part of the Tristan da Cunha group, is one of the UKOT’s most important sites for biodiversity, as recognised by the island’s status as a World Heritage Site, Site for Zero Extinction and Endemic Bird Area.

The major threats to Gough Island are the presence of invasive species, especially the House Mouse and the plant Sagina procumbens, as well as the impact of longline fishing mortality on albatrosses and petrels. Research has established that mice are responsible for unsustainable breeding failures of the Tristan Albatross and Atlantic Petrel, accounting for the mortality of upwards of 400,000 chicks each season. Recent population estimates of the endemic Gough Bunting indicate that this species is in rapid decline as a result of mice. Longline mortality at-sea impacts upon at least five species of Gough’s resident seabirds, including the Tristan Albatross. A recent evaluation of these threats has led BirdLife International to upgrade both the Tristan Albatross and Gough Bunting to Critically Endangered, and upgrade the Atlantic Petrel to Endangered. Five other bird species on Gough are Globally Threatened.

The plant Sagina procumbens is currently restricted to coastal cliffs near the weather base, where it was discovered in 1999. A long-term eradication programme is underway to prevent this species spreading and to eliminate it from Gough Island. If Sagina were to spread to upland areas there would be far reaching consequences to Gough’s unique invertebrate and plant communities, as well as to the island’s status as a World Heritage Site.

This project will place a two-person team on Gough Island for one year. Four key objectives will be met: 1, to undertake the key research necessary to determine the best approach for a mouse eradication; 2, to continue with the containment and eradication of Sagina; 3, to repeat long-term monitoring of Gough’s breeding bird populations to assess trends and the impact of current threats; and 4, to continue demographic research on the Tristan Albatross and Gough Bunting to determine the impact of mice predation on these two Critically Endangered species.

By placing a team on Gough for one year this project will resolve key issues identified by OTEP project TDC 203, allow the continuation of OTEP project TDC 403 at a critical point in the control of Sagina, repeat long-term monitoring of bird populations as supported by the UK FCO, and complete key research activities previously supported by the RSPB and University of Cape Town. Through utilising the South African National Antarctic Programme supply vessel the S.A. Agulhas to access and undertake work on Gough, the project will not impact on berth requirements for Tristan da Cunha, or necessitate the expense of chartering a dedicated vessel.

Contact Details

Dr Richard Cuthbert, The Lodge, Sandy, Bedfordshire, SG19 2DL, UK, Tel: +44 (0)1767 693085; Fax:+44(0)1767 685079, Email: richard.cuthbert@rspb.org.uk