Conservation status and management of the Gove Crow Euploea alcathoe enastri (Lepidoptera: Nymphalidae), a threatened tropical butterfly from the indigenous Aboriginal lands of north-eastern Arnhem Land, Australia

Abstract

The Gove Crow butterfly, Euploea alcathoe enastri Fenner, 1991, is restricted to Gove Peninsula of north-eastern Arnhem Land, a remote area of northern Australia. The subspecies has been listed as an Endangered taxon under federal and Northern Territory legislation, and represents one of only a few cases in the Australian Region in which a tropical butterfly has been targeted for species-orientated conservation. However, accurate status evaluation and conservation management have been hampered by lack of detailed information on spatial distribution, critical habitat, and the extent and severity of threatening processes. Surveys carried out during 2006–2008 indicate that the subspecies has a limited geographical range (extent of occurrence approximately 6,700 km²) within which it is recorded from 11 locations or subpopulations embracing a total of 21 sites. Most sites comprise discrete habitat patches that are relatively small in area (<10 ha) within which adults are localised and occur in low abundance (<15 h⁻¹). Of the four major habitat types in which E. alcathoe enastri was detected, only mixed paperbark tall open forest with rainforest elements in the understorey and rainforest edge (i.e. the ecotone between evergreen monsoon vine-forest and eucalypt/paperbark woodland) comprise breeding habitats. These habitat patches were always associated with permanent creeks or perennial groundwater seepages or springs that form swamplands, usually along drainage lines or flood plains in coastal or near coastal lowland areas. Major threats identified at the site level are habitat modification through altered fire regime and habitat disturbance by feral animals (buffalo, pig); potential threats at the landscape level include habitat loss through invasive species (grassy weeds, tramp ants) and global climate change. However, since critical breeding areas are subject to natural disturbance by both fire and flood, and occasionally cyclonic events, an optimal balance in disturbance regime is probably required to sustain breeding populations. Although E. alcathoe enastri is a narrow-range endemic that is ecologically specialised, there is no evidence of decline. Accordingly, the conservation status of the subspecies should be regarded as Near Threatened (‘Conservation Dependent’) under IUCN criteria. Components for an effective long-term conservation management plan of the butterfly and its habitat, which largely depend on the cooperation of traditional landowners and involvement of local indigenous ranger groups, are briefly discussed.

Appendix

Priority conservation management actions for Euploea alcathoe enastri.

• 1. Development and involvement of local indigenous rangers. All sites of E. alcathoe enastri occur on private lands owned by the Yolngu Aboriginal people of north-eastern Arnhem Land. Indeed, some sites surveyed were classed as ‘sacred sites’ that can only be accessed in the presence of senior traditional owners. Much of the range of the butterfly lies within the Indigenous Protected Areas: subpopulations 6–8 occur on lands managed by Dhimurru Land Management Aboriginal Corporation (DLMAC), while subpopulations 3–5 and 9–11 fall under the management of the Yirralka Laynhapuy Rangers. Subpopulations 1 and 2 occur in non-protected areas and fall within the jurisdiction of the Gapuwiyak Aboriginal Community, which currently does not have a local indigenous ranger group. Successful long-term conservation management of the butterfly and its critical habitat is thus dependent on cooperation of traditional landowners and involvement of the two local indigenous ranger groups.

• 2. Education, community awareness and fire management. The wet monsoon forest patches on Gove Peninsula contain a suite of resources that are of cultural and spiritual significance to the Yolngu community. These resources include food, timber, fibre, medicine and spears, but the forests also comprise an important place for dreaming stories and spirits. There is an urgent need to ensure that customary knowledge is not lost but passed on from senior traditional owners to the next generation. A program needs to be established in which elders and community leaders are employed to gather, teach, disseminate and transfer cultural skills and knowledge. Such a program would include traditional burning practices, ethnobotany, hunting techniques and traditional dances, as well as the conservation needs of E. alcathoe enastri and its critical habitat. This may be the only way to ensure that the overall burning pattern is not disrupted because there is evidence that severe habitat modification is already occurring at some sites through altered fire regime.

• 3. Monitoring to assess threats. Although habitat disturbance by feral animals (buffalo, pig) is currently not significant, monitoring of known sites is recommended to detect possible changes in severity by these animals, as well as to detect potential threats such as invasion of grassy weeds and Yellow Crazy Ants. In addition, the butterfly has the potential to be used as an indicator taxon to assess general environmental health because of its ecological specialisation. Adults of E. alcathoe enastri are large, spectacular and readily identified in the field. Therefore, changes in its occurrence and abundance may reflect adverse changes to the general health of its critical habitat as a whole. Such a monitoring programme could be achieved by visually assessing and digitally recording habitat condition within selected sites on an annual basis by two rangers. Because of the low topographic relief of Gove Peninsula, monitoring is also needed to assess possible long-term environmental changes in sea-level, temperature and water table brought about by global climate change.

• 4. Control of exotic species. At present there is no control program of water buffalo and feral pig on Gove Peninsula. Should these threats become significant, a feral animal control strategy will be needed, which should be undertaken by the indigenous ranger groups with support from the Northern Territory Parks and Wildlife Service (P&WS). Perennial Mission Grass and Gamba Grass have the potential to invade and become serious weed problems on Gove Peninsula, and control and eradication of known infestations and the need to maintain vigilance against new outbreaks are therefore high priorities. Survey, monitoring and control of Yellow Crazy Ant is currently been undertaken on Gove Peninsula by the Crazy Ant Management Group coordinated by CSIRO Sustainable Ecosystems, Tropical Ecosystems Research Centre, DLMAC, P&WS of the Northern Territory Government, the Commonwealth Department of the Environment, Water, Heritage and the Arts and Northern Land Council, with funding from the Natural Heritage Trust. Due to the size and extent of the infestation the program has now shifted its focus from eradication to methods for control and containment (B. Hoffman, pers. comm.).