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

摘要

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 kmpo) 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 hp#). 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.