National Recovery Plan for the Christmas Island Shrew (Crocidura attenuata trichura)
Prepared by Martin Schulz for
The Department of the Environment and Heritage, 2004
ISBN 0 642 55011 5
Part D: Objectives, criteria and actions
- Recovery objectives and timelines
- Performance criteria
- Evaluation of performance
- Management practices
The overall objectives of this recovery plan are to:
- clarify the taxonomic status of the Christmas Island Shrew,
- clarify the current status and distribution, and
- maximise the opportunity for the viability of this species in the wild.
Proposed measures for habitat protection and control or eradication of the crazy ant should assist the survival of any extant populations.
Specific objectives for the five years of this Recovery Plan are:
- Objective 1: To clarify the taxonomic status from existing museum specimens.
- Objective 2: To assess the current status and distribution through targeted surveys.
- Objective 3: To control the abundance and spread of the crazy ant
- Objective 4: To establish captive breeding populations from any extant populations, pending mitigation of all potential threats.
- Objective 5: To effectively protect and manage any extant populations
- Objective 6: To identify habitat critical to survival, including shelter, breeding and foraging habitat.
- Objective 7: To determine threatening processes affecting the species.
- Objective 8: To develop and implement a community awareness program to assist in the location of previously undetected populations.
Performance Criteria listed below match the corresponding Objectives:
- Criterion 1: Taxonomic status of the Christmas Island Shrew resolved.
- Criterion 2: Current conservation status and distribution determined.
- Criterion 3: Abundance and spread of crazy ant is less than at 2002 levels, with all high-density supercolonies reduced by 99% of their original densities.
- Criterion 4: Captive breeding populations established with the aim of reintroduction once potential threat control has been achieved.
- Criterion 5: Any identified extant populations protected and population numbers increase.
- Criterion 6: Habitat critical to survival investigated and determined.
- Criterion 7: Threatening processes determined, and actions taken to control them.
- Criterion 8: Increased knowledge of the shrew amongst island residents, an enhanced ability amongst islanders to identify the species from other small mammals and guidelines on what to do if a shrew is found.
The plan's performance to be reviewed by an Island Recovery Team as proposed for avifauna by Garnett & Crowley (2000). This recovery team to be established with the primary objective of developing and implementing island-wide conservation management and recovery plans, including for the Christmas Island Shrew. The Recovery Team to review and evaluate progress with respect to this Recovery Plan annually over the five-year period. This recovery team should comprise:
- on-island representatives (including PAN staff, a Shire of Christmas Island representative, and other local members as deemed appropriate), and
- off-island representatives (including two or more members of the scientific community with first-hand knowledge of the island's ecology and endemic fauna).
In addition to annual review, implementation of the plan should be reviewed at the end of 5 years (as required under the EPBC Act). If the Christmas Island Shrew is not found during the life of this plan (see Action 2), the conservation status listing should also be reviewed, and if appropriate, the species nominated for listing as Extinct.
The Actions are to follow two distinct stages:
Stage 1 - Prior to location of extant populations
This stage incorporates actions to be undertaken prior to the location of extant populations of the Christmas Island Shrew.
Action 1: Investigate the taxonomic status of the shrew (Obj. 1; Perf. Crit. 1).
Genetic studies, using (dry or ethanol preserved) museum specimens can determine the phylogenetic relationship with closely related shrews in Java and other parts of southeast Asia. This can be achieved by analysing molecular sequence data, such as mitochondrial cytochrome b gene or the control region of D-loop. Taxonomic investigations of Crocidura shrews have been conducted indicating the potential availability of primers of closely related species, for example C. attenuata (Ruedi & Vogel 1995, Motokawa et al. 1997, Motokawa et al. 2000) and C. fuliginosa (Ruedi et al. 1990, Ruedi & Vogel 1995, Ruedi et al. 1998, Querouil et al. 2001). This could be done in various institutions, such as the Evolutionary Biology Unit, South Australian Museum or the Centre for Environmental Adaptation and Stress Research, University of Melbourne. Although this action will determine the taxonomic status, even if genetic studies show that the Christmas Island Shrew is not a distinct species or subspecies (from those found in Asia), it still represents a unique element of Australian fauna which meets criteria for threatened listing under the EPBC Act, and therefore requires a recovery plan outlining recovery actions.
Action 2: Investigate current status and distribution (Obj. 2; Perf. Crit. 2).
Before any remedial work to aid recovery, it must be determined if the shrew is extant. Once 're-discovered', information on current status and distribution is essential to manage recovery. Targeted surveys of potential habitat in rainforest throughout the island, by suitably qualified and experienced personnel, should be conducted twice annually over the five-year period, or until populations have been located, and the status and distribution determined. Appendix 1 details the suggested targeted survey approach. If after 5 years, the community awareness program, feral animal control actions and practices, and habitat protection measures have been implemented, and no shrew is found, nomination for listing as Extinct under the EPBC Act should be considered.
Action 3: Develop wildlife management program for potential habitat outside the Christmas Island National Park (Obj. 3, 5 & 6; Perf. Crit. 3, 4, 5 & 6).
The majority of primary rainforest outside the National Park is publicly owned, by the Commonwealth. To achieve protection of threatened species, including any remaining extant populations of the shrew, outside the national park, it is essential that a considered approach be adopted through developing a comprehensive wildlife management program. Such an approach will assist PAN in negotiations over development proposals, allow for the input of relevant decision-makers and landholders, and facilitate greater certainty for environmentally sensitive developments. The plan should also allow for adaptive management as better information becomes available on the Christmas Island Shrew and other threatened species, in particular whether the shrew is extant, and if so what habitat is critical for survival.
Action 4: Control abundance and spread of crazy ant (Obj. 3, 5 & 7; Perf. Crit. 3, 5 & 7).
In September 2002 an aerial baiting program was undertaken, with all known supercolonies treated with insecticide. Results so far indicate that the program was successful in controlling supercolonies over 2500 ha of Christmas Island. Crazy ants are still present in low densities on Christmas Island. PAN staff will continue to monitor any new supercolony formation and treat by hand baiting over the next few years.
Action 5: Implement community awareness program (Obj. 2, 5 & 8; Perf. Crit. 2, 5 & 8).
All confirmed records over the past century (ie. 2) have been accidental, rather than targeted. Given the species' rarity and the difficulty using traditional capture techniques, due to the various crab species, it is likely that future records will also be accidental. To enhance the profile of the shrew amongst islanders and interest groups, a community based awareness program is required. This should be based on a information brochure, to encourage reporting and assist distinguishing the shrew from other small mammals, such as the house mouse Mus musculus and immature black rat. The program should improve on publicity used previously to enhance the profile of the shrew, and include instructions on what to do if one is seen/found. It should also clearly explain what conservation actions will occur (and why) if shrews are found. Additionally, PAN staff should conduct information sessions with school groups, field staff from various organisations (e.g. Shire of Christmas Island, CI Phosphates Pty Ltd and Asia Pacific Space Centre), and other interest groups.
This community awareness program must be coupled with confirmation of reported sightings by qualified PAN staff. On confirmation, an assessment of the site's attributes, and a survey within similar habitat in the vicinity should be undertaken by suitably qualified and experienced personnel to identify the extent of the population. It would be valuable for PAN to establish a database for sightings, and devise procedures or protocols for assessing any reported sighting, and the handling of any individuals located.
Stage 2 - Subsequent to location of extant populations
Action 6: Establish captive breeding population (Obj. 3, 4, 5 & 7; Perf. Crit. 3, 4, 5 & 7).
When an extant population is located, it is important that a captive breeding population be established to assist in the continuing survival of the species, with the view to reintroduction once crazy ants and other potential threats are controlled. Evidence from the LB4 individual captured in 1985 indicates that the species copes well in captivity, although food provision was time consuming (J. Tranter, DEH, pers. comm.). It is preferable that captive animals be held on Christmas Island to avoid transportation stress, and exposure to new diseases and different climatic conditions. Such a captive population must also be protected from direct or indirect (e.g. through food provided) exposure to ant bait, and from potential predators common around the Settlement, such as the wolf snake, black rat and cat. Alternatively, captive breeding populations could be established in recognised zoos on mainland Australia where appropriate quarantine, disease-management and climatic conditions can be provided. The feasibility of establishing the captive populations in the same holding facility as proposed for some endemic Christmas Island bird species (Garnett & Crowley 2000) should be investigated if the shrew is 'rediscovered'.
Action 7: Effective management of populations (Obj. 4, 5, 6 & 7; Perf. Crit. 4, 5, 6 & 7).
The location of any site supporting extant populations must be identified as habitat critical for the species. Steps must be taken to protect the area to ensure continuing survival and aid in population increase. Based on the limited information available recommended protection of the area in which a population is found needs to include no further habitat loss within at least 1km of the outer limits of the population detected; no new roading through the identified area; predator control (including the feral cat and black rat), as well as control and monitoring of the crazy ant. Further actions could include removal of individuals into a captive population (see Action 5). Where a population is located outside the National Park, appropriate management strategies are to be devised and implemented with the relevant interest groups, landowners or managers. Research relevant to the protection of any extant population is a high priority, and must include identifying habitat critical to survival and threatening processes.
Action 8: Identify and describe habitat critical (Obj. 3, 5, 6 & 7; Perf. Crit. 3, 5, 6 & 7).
When plentiful, the Christmas Island Shrew was recorded in rainforest extending from the shoreline to the plateau. However, in terms of identifying components of this vegetation comprising critical foraging, breeding and sheltering habitat, little information is available. For any populations of shrews located, an important action is to identify critical microhabitat within the rainforest used for foraging, shelter and breeding purposes. Additionally, it will be important to assess usage of regrowth areas, sites infested by crazy ants and weeds, and the importance of edge effect. Such an action will assist in the identification and protection of other areas of potential habitat critical to survival, and aid in targeted surveys to locate additional populations.
Action 9: Identify threatening processes (Obj. 3, 4, 5, 6 & 7; Perf. Crit. 3, 4, 5, 6 & 7).
The threatening processes affecting the viability of Christmas Island Shrew populations have not been identified, although disease, habitat loss and habitat alteration are suspected to have been important factors in their decline. It is also likely that the spread of the crazy ant will have a deleterious effect on remaining populations. However, it is important with any extant populations, to assess components of the site that may assist in the identification of threatening processes. Confirmation of threatening processes is critical for long-term effective management of the species. Management practices must then be determined to reduce the impact of identified threats on located populations of the shrew.
It is difficult to identify specific management practices to avoid adverse impacts on the Christmas Island shrew due to the lack of information on the species. Many of the Actions outlined above are designed to determine specific management practices. Until these have been determined, the broad interim management practices below should be adopted to minimise potential further declines:
- No removal of primary plateau rainforest within Christmas Island National Park;
- Implementation of the Invasive Ants on Christmas Island Action Plan;
- Continuation of liaison with AQIS and WAQIS to ensure tight quarantine controls to prevent the accidental introduction of new diseases and exotic pests;
- Feral Cat and Black Rat control programs within primary plateau and terrace rainforest;
- Maintenance of existing habitat quality of primary rainforest through strategies to minimise spread of exotic weeds following the Weed Management Strategy (Hart 1998); and
- Adoption of strategy to avoid wildfires within potential shrew habitat.
Removal of any primary plateau and terrace rainforest could result in a significant impact on the Christmas Island shrew and should be referred to the Commonwealth Environment Minister under the EPBC Act. Removal of primary plateau and terrace rainforest on vacant crown land or leasehold land should not occur without intensive targeted surveys for the Christmas Island Shrew (see Appendix 1).