Euploea alcathoe enastri (Gove Crow Butterfly)

Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)

1. Scientific name, common name (where appropriate), major taxon group

Euploea alcathoe enastri (Gove Crow Butterfly)

2. Description

The Gove Crow Butterfly is a large black butterfly with white spots near the edges of the wings. The wings are velvety-black on top and blackish-brown below.

3. National Context

The Gove Crow Butterfly is confined to the Gove Peninsula, north-eastern Arnhem Land, Northern Territory. It was first discovered in 1988 and is only known from four sites on the Gove Peninsula (Fenner 1991, 1992). Only adults have been found, and they always occur in or closeby patches of tall forests that are associated with groundwater seepage. Little is known about the ecology of this species.

The Gove Crow Butterfly is listed as 'Endangered' under the Northern Territory Parks and Wildlife Conservation Act 2000.

4. How judged by TSSC in relation to the EPBC Act criteria.

TSSC judges the species to be eligible for listing as endangered under the EPBC Act. The justification against the criteria is as follows:

Criterion 1 - Decline in numbers

The Gove Crow Butterfly is known from only four sites on the Gove Peninsula in north-eastern Arnhem Land. It is reported to be abundant within its known habitat, patches of tall forests that are associated with groundwater seepage. There is no further information on population size.

There is insufficient information available against this criterion. Therefore, the species is not eligible for listing under this criterion.

Criterion 2 - Geographic distribution

The Gove Crow Butterfly was first discovered in 1988 at Rocky Bay near Yirrkala on the Gove Peninsula in north-eastern Arnhem Land. It is now known from three other nearby sites (Fenner 1991, 1992). Its distribution is restricted and fragmented. It has a linear range of approximately 80 km, a known extent of occurrence of about 2000 km2 and an area of occupancy estimated to be less than 500 km2.

Habitat: To date, only adults of the Gove Crow Butterfly have been seen, and they have only been seen in or closeby patches of tall forests that are associated with groundwater seepage. There is no firm data on breeding habitat, but it is thought that the habitat where the adults have been found is the likely main breeding habitat. The food plants on which the larvae feed may include a local milkweed, Tylophora benthamii, as a female Butterfly was seen apparently ovipositing on a creeper that was this species or one similar to it (Fenner 1991).

Survey effort: It seems likely that the distribution of the Gove Crow Butterfly is truly restricted, as there has been a reasonable effort to survey for this species in suitable habitat over the last 14 years. It is a conspicuous large black butterfly, with white spots near the edges of the wings, and would not be easily missed in surveys. Experts have advised that western Arnhem Land has been well surveyed for this Butterfly, although inaccessible areas in eastern Arnhem Land have been less well surveyed. It seems unlikely that the Butterfly will be found away from the Gove Peninsula as this Butterfly's habitat, tall forest that is associated with groundwater seepage, appears to be mainly restricted to a limited number of small, widely scattered patches on the Gove Peninsula. Some specific surveys for this Butterfly have been conducted in the region of the Gove Peninsula, including a recent survey in September 2002, however, no new locations have been found.

Threats: There are major environmental changes occurring on Gove Peninsula which could lead to a decline in the Gove Crow Butterfly. These significant changes include the spread of Crazy Ants Anoplolepis gracilipes and the changes occurring in fire regimes, particularly those resulting from the spread of the giant African perennial, Mission Grass Pennisetum polystachion. In addition, the recent improvement in roads in the area may also be resulting in increases in the frequency and extent of fires.

Crazy Ants: The permanently wet, spring-fed forest patches that are the habitat of the Gove Crow Butterfly are also likely to provide favourable habitat for the highly invasive Crazy Ant. This Ant has become established in many tropical and subtropical areas throughout the world. It was first recorded on the Australian mainland, in East Arnhem Land, in May 1990. Surveys in 1999 found Crazy Ants were spread over five river drainage systems in East Arnhem Land (including the Gove Peninsula), covering an area of about 2,500 km2 . As such a large area is infested, it is thought that an eradication campaign will be extremely difficult (Young et al. 2001). Experts state that it is now found at around 40 locations throughout the Gove Peninsula and surrounding areas. In September 2002, Crazy Ants were found for the first time at one of the four known locations of the Gove Crow Butterfly. This location is where most sightings and collections of this Butterfly have been made. One expert has advised that, given the Crazy Ant's propensity for colony expansion, it is likely to become established throughout much of the habitat of the Gove Crow Butterfly.

Researchers recently concluded that the Crazy Ant is a "serious threat to the invertebrate fauna of monsoon rainforests in northern Australia" (Young et al. 2001). A formal study on the ecological impacts of the Crazy Ant on Gove Peninsula has just begun but initial observations show a loss of all native ant species and a significant reduction in all other native invertebrates in the areas that the Crazy Ant occupies. One expert noted that if Crazy Ants invaded the Gove Crow Butterfly's habitat at sufficiently high densities, there would be little chance of this Butterfly's larvae surviving. The Crazy Ant has a long history of environmental damage across the tropics, including on Christmas Island (Indian Ocean), where it is damaging, amongst other things, rainforest vegetation and Christmas Island Red Crabs (Gecarcoidea natalis). In other countries, there are numerous reports of introduced Crazy Ants displacing other invertebrate species (especially ants and spiders) and altering the floral compositions of habitats (Young et al. 2001).

Fire: On the Gove Peninsula the fire regime that has occurred in the past is likely to be changing as a result of the spread of Mission Grass and the improved human access to remote areas. These factors can produce intense and frequent fires that adversely affect forest patches, including the few where the Gove Crow Butterfly is known to occur. If the forest patches that contain this Butterfly are burnt, the food plant of the eggs, larvae and pupae would be destroyed.

Introduced African Mission Grass has only recently become established on the Gove Peninsula, and it has been recorded near the centre of the Gove Crow Butterfly's distribution. The spread of Mission Grass into the savanna areas in the Darwin area is one of the key factors implicated in the severe decline of rainforest cover that has occurred in this region, as it caused significant changes to the local fire regime (Panton 1993). In the Darwin area, savanna areas that contain Mission Grass have much greater fuel loads (3-5 times greater) than those that contain only natural grasses. Also, as Mission Grass cures and dries later than native grasses, it can burn later in the Dry season than native grasses, and at a time of year when the landscape is drier and windier. Therefore, savanna areas with Mission Grass have much hotter, destructive fires that occur throughout more of the year than areas containing only native grasses. Round Darwin, forest patches bordering savanna areas with Mission Grass areas have shrunk and eventually disappeared because of the impact of the more intensive and constant fires on their edges.

On the Gove Peninsula there are some attempts being made to manage the spread of Mission Grass. However, if Mission Grass spreads, the resulting fire regime on Gove Peninsula is likely to be similar to that seen in the Darwin area, and it will threaten the integrity of forest patches and cause many to disappear, which may include those few where the Gove Crow Butterfly is found.

There are some claims that fire on the Gove Peninsula will increase in frequency and extent as a result of recent upgrading in the local road networks. In the Darwin area, fires are often deliberately lit (Panton 1993). Therefore, as access to previously inaccessible areas on the Gove Peninsula is improved, the likelihood of the deliberate lighting of fires may increase. However, there appear to be no published studies on this issue for this area.

It is also generally acknowledged that road building, road maintenance and vehicles are often associated with the spread of weeds, such as Mission Grass. Some experts believe that it is only a matter of time before the introduced weed Gamba Grass (Andropogon gayanu) reaches the Gove Peninsula. Its impact on the habitat of the Gove Crow Butterfly will be similar to that caused by Mission Grass. In addition, feral animals, particularly Water Buffalo Bubalus bubalis and feral Pigs Sus scrofa, are on the Gove Peninsula. Such animals are known to damage monsoon rainforest habitat, and may also damage the habitat where the Gove Crow Butterfly occurs. Cyclones could also do considerable damage to the habitat of the Gove Crow Butterfly.

The Gove Crow Butterfly is known from only four sites on the Gove Peninsula, and has a fragmented distribution, a known extent of occurrence of about 2000 km2 and an area of occupancy estimated to be less than 500 km2. There are a number of threatening processes that are operating on the Gove Peninsula that are likely to lead to declines in this Butterfly's area of occupancy, extent of occurrence, quality of habitat and number of mature individuals. In particular, the Gove Crow Butterfly is threatened by the ecological impacts that may be caused by the spread of Crazy Ants Anoplolepis gracilipes and the impacts on their habitat that may result from altered fire regimes, principally those caused by the spread of Mission Grass.

Therefore, the species is eligible for listing as endangered under this criterion.

Criterion 3 - Population size and decline in numbers or distribution

The Gove Crow Butterfly is known from only four sites on the Gove Peninsula in north-eastern Arnhem Land. It is reported to be abundant within its known habitat. There is no further information on population size.

There is insufficient information available against this criterion. Therefore, the species is not eligible for listing under this criterion.

Criterion 4 - Population size

The Gove Crow Butterfly is reported to be abundant within its known habitat on the Gove Peninsula. There is no further quantitative information on population size.

There is insufficient information available against this criterion. Therefore, the species is not eligible for listing under this criterion.

Criterion 5 - Probability of extinction in the wild

There is no quantitative data available against this criterion.

Therefore, the species is not eligible for listing under this criterion.

5. Conclusion

The Gove Crow Butterfly has a restricted, fragmented distribution being known from only four sites on the Gove Peninsula. It has a known extent of occurrence of about 2000 km2 and an area of occupancy estimated to be less than 500 km2. There has been a reasonable effort to survey for this species, and it is unlikely that it occurs at many more sites than those currently known. There is reasonable evidence to suggest that this Butterfly may be adversely affected by a number of threatening processes that are currently at work on the Gove Peninsula. In particular, the species is threatened by the ecological impacts that may result from the spread of Crazy Ants and the impacts on habitat that may result from altered fire regimes, principally those alterations that may result from the spread of Mission Grass.

The species is eligible for listing as endangered under criterion 2.

6. Recommendation

TSSC recommends that the list referred to in section 178 of the EPBC Act be amended by including in the list in the endangered category:

Euploea alcathoe enastri (Gove Crow Butterfly)

Publications used to assess the nomination and references cited

Braby, M. F. 2000. Butterflies of Australia. Their identification, biology and distribution. Vol. 2. CSIRO Publishing, Melbourne, pp. 609-610.

Fenner, T.L. 1991. A new species of Euploea alcathoe (Godart) (Lepidoptera: Nymphalidae) from the Northern Territory, Australia. Aust. Ent. Mag. 18: 149-55.

Fenner, T.L. 1992 Correction and addendum. Aust. Ent. Mag. 19: 93.

Young, G.R., et al. 2001. The Crazy Ant Anoplolepis gragilicipes (Smith) (Hymenoptera: Formicidae) in East Arnhem Land, Australia. Aust. Entomologist 28: 97-104

Kean, L. and Price, O. (in press). The extent of Mission grass and Gamba grass in the Darwin region of Australia's Northern Territory. Pacific Conservation Biology

Kitching, R. L., Sceermeyer, E., Jones, R. E. and Pierce, N. E. (eds.) 1999. Biology of Australian Butterflies. Monographs on Australian Lepidoptera vol. 6. CSIRO Publishing, Melbourne. p. 198.

Lambkin, T. A. 2001. The life history of Euploea alcathoe monilifera (Moore) and its relationship to E. a. eichhorni Staudinger (Lepidoptera: Nymphalidae: Danainae). Australian Entomologist 28 (4), 129-136.

Panton, W. J. 1993. Changes in post World War II distribution and status of monsoon rainforests in the Darwin area. Australian Geographer 24 (2), 50-59.

Russell, Smith,. J. 1998. Proceedings from the North Australia Fire Management Workshop, Darwin, 24-25 March 1998 (eds. P. Jacklyn and J. Russell-Smith). Tropical Savannas CRC, Darwin.

Russell-Smith, J. and D.M.J.S. Bowman. 1992. Conservation of monsoon rainforest isolates in the Northern Territory, Australia. Biological Conservation 59: 51-63.

Sands, D.P.A. and T.R. New. 2002. The Action Plan for Australian Butterflies. CD ROM. Environment Australia, Canberra.

Wilson, C. 2002. Threatened Species of the Northern Territory Information Sheet - Gove Crow Butterfly Euploea alcathoe enastri. NT Nat. Parks and Wildlife Commission.

Young, G. R., Bellis, G. A., Brown, G. R. and Smith, E. S. C. (2001). The crazy ant, Anoplolepis gracilipes (Smith) (Hymenoptera: Formicidae) in east Arnhem Land, Australia. Australian Entomologist 28 (3), 97-104.

Conservation advice

The Gove Crow Butterfly is a large black butterfly only known from four sites on the Gove Peninsula, north eastern Arnhem Land, Northern Territory (Northern Territory NRM region). It occurs in patches of tall forests associated with groundwater seepage.

Key threats to the Gove Crow Butterfly include: the ecological impacts of crazy ants; changes in fire regime (e.g. increasing frequency and extent due to the spread of African Mission Grass and increasing human access); and feral animals (e.g. water buffalo and feral pigs).

The priority recovery and threat abatement actions required for this species are:

  • protect the four known sites from the adverse impacts of crazy ants;
  • monitor and manage access to the four sites by humans; and
  • control feral animals.

This list does not encompass all actions that may be of benefit to this species, but highlights those that are considered to be of the highest priority at the time of listing. Longer term issues that should be considered in broader landscape, regional and or recovery planning include an appropriate fire management plan for the Peninsula incorporating an appropriate fire strategy for the Gove Crow Butterfly and the control of African Mission Grass.

Threat Abatement Plans are currently in preparation for 'Predation, Habitat Degradation, Competition and Disease Transmission by Feral Pigs' and in relation to the impacts of invasive tramp ant species. No Recovery Plan is currently in place for the Gove Crow Butterfly.

Priority for the development of recovery plan: Medium