Threatened Species and threatened ecological communities
Recommendation to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on a public nomination for a species listing on the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)
Pteropus conspicillatus (Spectacled Flying-fox)
Known in Australia from major rainforest tracts in North East Queensland and Torres Strait. The species also occurs in Papua New Guinea and the Solomon Islands.
TSSC judges the species to be eligible for listing as vulnerable under the EPBC Act. The justification against the criteria is as follows:
There is much anecdotal evidence that the Spectacled Flying-fox has declined in abundance over the last century, but little quantitative support for this argument. Many experts comment that there now appear to be fewer camps, and cite extensive habitat clearing, a decline in range, and increased mortality through pest management practices at orchards and tick paralysis as likely causes. However, there are no robust count data to support these observations.
Spectacled Flying foxes are highly mobile and have complex and irregular movement patterns primarily determined by seasonal nectar flows. This characteristic makes estimating population size a difficult task. In the last three years, there have been attempts to undertake this across the range of the species in the wet tropics (Ingham to Cooktown) through synchronised counts of animals leaving camps at dusk. These counts suffer from a number of deficiencies with respect to population assessment: they are a short time series dataset, the accuracy and precision of the counts is undefined, issues of count technique such as observer variability need refinement, and some camps are not counted due to resource issues or because their location is unknown.
The number of adult individuals counted in these surveys has ranged from 153,000 in 1998, to around 80,000 in 1999 and 2000 (estimated error 20%). These figures are likely to have under-estimated the true population size because of the difficulty of seeing bats leaving camps once night falls. Also, the northern population on Cape York Peninsula (McIlwraith Range and Iron Ranges) has not been surveyed, although it is likely to be much smaller.
Two experts have recently modeled the vulnerability of both the Grey-headed Flying-fox, Pteropus poliocephalus, and the Spectacled Flying-fox, to population decline and extinction using basic parameters of reproduction obtained from captive breeding data. This analysis shows that flying-fox populations have a low capacity for increase and depend on low levels of natural mortality and high survival of adults to maintain stable population levels. These experts conclude that current death rates of the Spectacled Flying-fox caused by the use of electrical grids (or 'fyre-foxes') to protect fruit crops places the wet tropics population at risk.
Two other experts challenged the validity of the inputs to the model, in particular, the extrapolation of data from captive animals to the wild population, and the dismissal of published empirical evidence from wild populations. The model essentially assumes that flying-foxes do not breed until three years of age, based on observations of captive animals, but field based data is available for the closely related Black Flying-fox that indicates that females mature at two years. The sex ratio of flying-foxes in most camps is also closer to 70:30 (females:males), rather than the 1:1 ratio used in the model. Changes to these and other inputs to the model should be made to further explore the impacts of these influences on the population survival.
However, whilst the modeling is imperfect, it provides clear messages about the likely impact of increased mortality to adults. Sustained high levels of mortality additional to natural mortality would undoubtedly lead to population declines in the near future. Evidence is now available to indicate that this possibility is likely because large numbers of the Spectacled Flying-fox are being killed on electrocution grids established to protect orchards in the wet tropics in the main part of the Spectacled Flying foxes Australian range. There are currently 11 licensed grids in operation and the Queensland Department of Environment believes these grids cause the deaths of thousands of Spectacled Flying-foxes each year. Evidence from a Federal Court of Australia hearing (Booth v Bosworth, 2000) was provided which showed that 229 Spectacled Flying-foxes were killed over four nights on one property. It should be noted that these counts were only done on a small part of the property and its electrocution grid, so it is likely that the real level of mortality on this property is much higher. However, if the rate of observed mortality is consistent across the entire fruiting season at this orchard (2 months), then the mortality at this site alone is very extensive, and likely to exceed 3,500 animals. With the likelihood that similar levels of mortality are being achieved at the other 10 orchards using this form of crop protection, sustained electrocution of Spectacled Flying-foxes at these levels, added to natural mortality, is likely to lead to negative population growth and ultimately extinction of the species. As an example, modeling, assuming a total mortality rate of 30% for all age classes and a fecundity rate of 90% for females greater than 2 years old, predicts that the population will halve in nine years under this scenario, and suggests that at the current rate of decline it will be extinct (within the wet tropics) within 99 years. These assumptions are not unreasonable, given a maximum count for the wet tropics population of 153,000 animals.
The evidence on current population levels is equivocal. However, based upon the population modeling, and in the presence of high levels of non-natural mortality, it is reasonable to infer that there will be a substantial reduction in the existing population in the wet tropics in the immediate future. As this is where the bulk of the Australian population resides, the Spectacled Flying-fox is eligible for listing as vulnerable under this criterion.
Criterion 2 - Geographic distribution
The species is restricted to wet tropical areas in NE Queensland, ranging from Ingham to Cooktown in the south, with another population in eastern Cape York Peninsula. Despite extensive habitat loss (80%) in the coastal lowlands of tropical Queensland, the area of occurrence and occupancy is not considered to be so restricted as to be critical to the species survival, particularly given its ability to exploit alternative food sources.
Therefore, the species is not eligible for listing under this criterion.
Information on population estimates for the Spectacled Flying-fox is provided under Criterion 1. Given these numbers (lowest estimate 80,000 individuals), the estimated total number of mature individuals is not considered to be limited.
The geographic distribution of Spectacled Flying-fox is covered under Criterion 2. As stated above, its geographic distribution is not precarious, particularly given its ability to exploit both native and exotic food resources.
Therefore, the species is not eligible for listing under this criterion.
The data presented under Criterion 3 do not support listing under Criterion 4, in that the number of adult individuals is currently estimated to exceed 80,000.
Therefore, the species is not eligible for listing under this criterion.
There is no quantitative evidence available against this criterion. However, as mentioned above under Criterion 1, two experts have recently modeled the vulnerability of the Spectacled Flying-fox to decline and extinction using data obtained from captive breeding studies. This analysis shows that flying-fox populations have a low capacity for increase and depend on low levels of natural mortality and high survival of adults to maintain stable population levels. These experts conclude that current death rates of the Spectacled Flying-fox caused by the use of electrical grids or 'fyre-foxes' to protect fruit crops places the wet tropics population at risk.
The level of mortality associated with electrocution grids has been discussed above under Criterion 1. In summary, TSSC believes that there is good evidence to suggest that the levels of mortality being imposed through this form of crop protection are additive to natural mortality, and are likely to lead to negative population growth and ultimately extinction of the species. The example used above (mortality rate of 30% for all age classes, fecundity rate of 90% for females greater than 2 years old) uses parameters which are conservative in the face of this level of mortality. It predicts that the wet tropics population will halve in nine years, and be extinct within 99 years under this scenario.
Based upon the population modeling, and in the presence of high levels of non-natural mortality, the Spectacled Flying-fox is eligible for listing as vulnerable under this criterion.
The population of Spectacled Flying-foxes is likely to undergo in the immediate future a substantial reduction in numbers and faces extinction in the medium term. Mortality caused by the use of electrocution grids to protect fruit crops poses a significant threat to the wet tropics population. The combination of inferred declines and continuing threats justifies listing the species. The species is eligible for listing as vulnerable under criteria 1 and 5.
a) TSSC recommends that a review of the conservation status be undertaken in 2003.
b) TSSC recommends that the list referred to in section 178 of the EPBC Act be amended by including in the list in the vulnerable category:
Pteropus conspicillatus (Spectacled Flying-fox).