Publications
Environment Australia, November 1997
A two day 'National Threatened Frog Workshop' was held at the University of Canberra in November 1997 sponsored by Environment Australia, the NSW National Parks and Wildlife Service, the University of Canberra and the Worldwide Fund for Nature.
The Workshop brought together some 80 people from throughout Australia and overseas involved in frog research, management and policy development and included representatives from government agencies, educational institutions and non-government organisations.
Ray Nias*, Ross Alford, Keith McDonald and Mike Tyler
* World Wide Fund for Nature GPO Box 528 Sydney NSW 2001
There is a widespread acceptance and concern that a global and dramatic decline of amphibians is occurring. Declines are often occurring for no apparent reason in relatively undisturbed habitats, particularly at high altitudes. Recent research and trends in amphibian conservation were a major focus of the Third World Congress of Herpetology held in Prague, Czech Republic, 2-10 August 1997. A variety of potential causes have been postulated and research into these was reported at the congress, together with evidence of new declines and measures being carried out to conserve amphibians. Major areas of research include habitat loss and disruption, chemical pollutants, UVB radiation, climate change, invasive species and disease. A global scientific effort is being coordinated by the IUCN specialist group: Declining Amphibian Populations Task Force (DAPTF).
Stan A. Orchard
Canadian Amphibian and Reptile Conservation Network, including the IUCN/SSC Task Force on Declining Amphibian Populations in Canada (DAPCAN), 1745 Bank Street, Victoria, British Columbia, CANADA, V8R 4V7 (sorchard@islandnet.com)
The international research effort to unravel the mysteries of declining amphibian populations has had considerable "success" since its formation in 1992 - but how do we measure its success? More scientists are involved in studying the conservation biology of amphibians than ever before.
The communications links between amphibian researchers have never been better. Mountains of data are being gathered, analysed and the results published. Public awareness of the issues is improving and public sympathy appears to be growing. In spite of all this, there are still very few examples of how this newly acquired knowledge and public sentiment will be applied to successfully reverse declining population trends. Thus, while those of us involved in these research and monitoring efforts perceive success and growing momentum, from an amphibian survival perspective the future is not much brighter today than it was in 1992.
One of our espoused tenets is to promote means by which declines can be halted and reversed, but we may be largely ignoring this aspect of our work in our rush to make scientific discoveries. Ultimately, we should be striving to create a "frog-friendlier" world, and not simply adding more statistically defensible documents to the historical record of amphibian demise.
K.R. McDonald* and R.A. Alford#
* QLD Dept. of Environment PO Box 834 Atherton QLD 4883
# Dept. of Zoology and Tropical Ecology, James Cook University Townsville QLD 4811
Eleven frog species have declined or disappeared since 1985 and 1989 in the Central Mackay Coast and Wet Tropics Biogeographic Regions respectively.
Declining species are associated with rainforest streams in upland areas. Declines are sudden for highly susceptible species which have close association with streams. Despite considerable effort the causal factor(s) have not been determined.
Declining species are considerably different in taxonomic relationships, morphology, reproduction, behaviour and microhabitat preferences.
Species outside rainforests are under localised anthropogenic pressures especially in the sugar cane expansion areas of the coastal lowlands.
Current studies are focused on population monitoring by community groups, the Department of Environment and James Cook University. Recovery plans have been compiled but have not been signed off by Government. Future efforts need to address translocation experiments, management of water usage and wider community based participation in monitoring and surveys.
Michael Mahony
Department of Biological Sciences, The University of Newcastle, Callaghan NSW 2308.
This paper deals mostly with the bell frog species that occur/occurred in south eastern Australia, namely, Litoria aurea, L. castanea/flavipunctata, and L. raniformis.
There is now considerable support for the earlier reports that the tablelands populations of L. aurea, L. castanea/flavipunctata and L. raniformis, have disappeared. Reconstruction of the time at which the decline/disappearances occurred indicates a period in the early 1980's. Litoria castanea/flavipunctata occurred only on the tablelands, and is now presumed to be extinct. Litoria aurea is now restricted to lowland populations, and the distribution, abundance, and status of this species has been recently reviewed (see papers in Pyke and Osborne, 1996). The status of L. raniformis is less certain. Populations in the Murray River Valley appear to be robust, although no standardised method of estimating abundance have been applied.
The bell frogs are in some respects similar to the other Australian frogs which have declined; high altitude species and populations are effected. However, they differ from most other declining species; they are not stream, vernal pool or forest frogs, and declines were not restricted to uplands. L. aurea has declined over extensive areas at low altitude. Finally, the introduced Mosquito fish (Gambusia holbrooki) has been implicated in population reductions. In biology it is often the exception to the general pattern that helps focus attention on what is important and what is unimportant in a pattern. Litoria aurea provides one of the best models to understand the phenomenon of frog declines in Australia; it is the only declining frog that has been bred for several generations in captivity, several thousand offspring have been used in translocation programs, it is a relatively large species (adults 70 to 90 mm), and disease has been observed in several populations.
W.S. Osborne*, D.A. Hunter* and G.J. Hollis#
* Applied Ecology Research Group, University of Canberra
# Department of Natural Resources and Environment, Warragul VIC 3820
There has been no overall systematic field assessment of the status of frogs in the Australian Alps. There have, however, been several major surveys conducted for particular species of concern in this region. Specifically, over the last decade, extensive surveys have been conducted for the following species: Litoria verreauxii alpina (alpine tree frog), Pseudophryne corroboree (southern corroboree frog), P. pengilleyi (northern corroboree frog) and Philoria frosti (Baw Baw frog). These endemic high altitude species have all suffered extensive population declines, and all but P. pengilleyi have undergone extensive contractions of their geographic range. Persistence sites for L. v alpina occur at the lower altitudinal limit of the species and are all associated with artificial water bodies such as dams and gravel excavation pits. Persistence sites for P. frosti are also at lower altitudes where the species is associated with breeding sites in deep gullies in dense montane forests. P. corroboree appears to have contracted to the wettest part of its range and has declined at both high and low altitudes. P. pengilleyi has declined only at higher altitudes.
Populations of P. corroboree have been in decline since at least 1986, and the species has become extinct at over 80% of all former sites. This has resulted in a massive contraction of the geographic range of this endemic species. It is likely that without active experimental management, the species will become extinct within a few years. P. pengilleyi has not declined to the same extent as P. corroboree although all subalpine populations are in serious decline. It is still common at many montane sites, particularly in woodland and forest. Philoria frosti is confined to the Baw Baw plateau. Surveys undertaken in 1983 and 1984 indicated that it was widespread and abundant on the plateau. Surveys undertaken annually since 1994 indicate that this species has declined extensively and disappeared from much of the exposed plateau and more open areas. Most remaining breeding sites occur in deep gullies in dense montane forest.
Graeme Gillespie
Department of Natural Resources and Environment PO Box 137 Heidelberg VIC 3084
The temperate regions of south eastern Australia contain 12 species of frog which breed in streams. Of these, nine are obligate stream breeders and the other three are facultative. The current status of these species is reviewed in the context of reported population declines, and recommendations are made for future directions. Two of these species are currently considered to be endangered, one is vulnerable and three are insufficiently known, as listed in The Action Plan for Australian Frogs (Tyler 1997). One species (Litoria piperata) may have disappeared, and three species (L. booroolongensis, L. spenceri and M. balbus) have suffered major population declines in recent years. Six other species have been reported to have declined in some parts of their ranges, but their status is otherwise poorly known or believed to be secure. Only two species are not reported to have declined; however, survey and monitoring data are not adequate for a reliable assessment.
Knowledge of distribution and abundance is inadequate for most species. Systematic monitoring is currently only being conducted for a few species. A comprehensive monitoring program exists for only one species, L. spenceri. Knowledge of ecology and potential threatening processes are non existent for most species. A range of potential threatening processes exist throughout or in part of the ranges of these species. These include habitat destruction, introduced fish, forestry practices and grazing. There is a strong requirement for systematic surveys to ascertain the magnitude and nature of the observed declines. Research is required on habitat requirements and community ecology of these frogs, to specifically examine existing processes potentially responsible for observed declines.
Roberts, JD*, Conroy, S* & Williams, K#
*Department of Zoology, University of Western Australia, Nedlands, WA 6907
#Department of Conservation and Land Management, Central Forest Region, Boyanup Road, Bunbury, WA 6230
Three frog species are currently listed on Schedule 1 of the WA Wildlife Conservation Act: Geocrinia alba, G. vitellina and Spicospina flammocaerulea. They are the only frog species of conservation concern in WA.
Spicospina flammocaerulea - this species is now known from a total of 13 sites (two sites are further subdivided by roads) covering a range of approximately 150 km2. The area of suitable habitat has not been reliably estimated but is about 0.1 km2 at the largest known site. Eight of thirteen sites are in state forest (in six management blocks), five on private land. The species is known from three drainages: Kent, Frankland and Bow rivers. The impacts of fire are unclear. Peak numbers of calling males observed in 1994 post fire have never been matched since. Calling activity may be affected by temperature with frogs calling preferentially on very hot nights. Current field work aims to relate calling activity to temperature and to improve range resolution. The IUCN status is unclear pending current field work - probably vulnerable at worst.
Geocrinia vitellina - IUCN status - vulnerable. The species is known from six discrete drainages over 6 km2. Population monitoring has occurred at two sites, 1992 - 1996 indicated increasing population size associated with fire exclusion. However, one of two monitored populations declined in 1997 before burning. Wildfire in October 1997 burnt out three major populations, one on Geo creek and two on Spearwood Creek as well as burning part of Hutt Pool. Impacts of this fire are being monitored. There was immediate loss of males from the Geo Creek breeding site but long term impacts are unknown. Females and juveniles may be at much greater risk than calling males in spring fires.
Geocrinia alba : IUCN status - endangered. Recovery Plan 1995 recorded 54 populations (1983 - 1994) with 13 further subdivided by major roads or changes in adjacent land use for a total of 72 management units. By 1994, 14 sub-population sites had gone extinct. Surveys in 1997 have shown further extinctions and apparent population reduction in some small populations. Only 8 sites were known to have populations of more than 100 calling males in 1997. Current management strategies involve fencing sites on private land, maintenance of fuel reduction burn strategies on public lands (spring burns only) and encouragement to private land holders to eliminate burning from swamps. Causes of extinctions are unknown though on private land they are more common where there is adjacent cleared land. Current research is directed to developing PVA models and studies of egg mass ecology for directing introduction or reintroduction programs.
Reinier Mann* and Joseph Bidwell
* School of Pharmacy and Medical Sciences, University of South Australia, North Terrace, Adelaide SA 5000
Three questions are addressed in this presentation:
1. What are the chemical assaults to which Australian frogs are exposed?
Pesticides, salinity, industrial effluents, eutrophication, and endocrine disrupters (EDCs) are discussed.
2. What tools are available to study toxic effects on frogs?
There are few standardised tools available for assessing amphibian susceptibility to chemical contaminants. Standard Acute Toxicity tests allow for the incorporation of tadpoles, but there are no standard protocols for adults.
FETAX (Frog Embryo Teratogenesis Assay-Xenopus) has been used extensively over the last 7-8 years but has been developed to study potentially mutagenic compounds in vertebrates rather than provide a tool for frog conservation.
Microcosm/Mesocosm protocols have been used to study intra- and inter-specific community relationships and can be developed to study toxicology at an ecocosm level.
Field validation is required to determine whether indeed a given toxicant is available for uptake by frogs.
3. What are the problems associated with amphibian toxicology?
The frog/tadpole dichotomy presents the biggest problem for amphibian toxicology. The literature which deals with toxic effects in adults is sparse and lacks uniformity in methodology.
Species variability provides the strongest argument for a more thorough examination of as many species as possible where a potential threat has been identified.
A constant supply of test animals is impossible when relying on field collected animals, and highlights the importance of commercial suppliers.
Graeme Gillespie
Department of Natural Resources and Environment PO Box 137 Heidelberg VIC 3084
Many species of exotic fish have been introduced into Australia. Of major concern within Australia are carp, trout and Gambusia species, which have wide distribution within Australia and have invaded many frog breeding habitats. Research conducted on the impact of these species on amphibians overseas and within Australia is reviewed. Available information indicates that introduced fish may be having a major impact upon amphibian communities through predation of eggs and tadpoles. Several pond-breeding species are vulnerable to predation by the Mosquito Fish (Gambusia holbrooki) and it has been implicated in the declines of the Green and Golden Bell Frog (Litoria aurea). Brown and Rainbow Trout have been found to exert significant predation pressure upon several temperate riverine species. Trout are considered to be the major cause of decline of the Spotted Tree Frog (Litoria spenceri), and may be a major contributing factor in the declines of other temperate riverine species in New South Wales.
More research is required into the extent of impact of introduced fish in amphibian populations in Australia. Measures are required to exclude introduced predatory fish from critical frog habitat where feasible, and limit further introductions.
Jean-Marc Hero1, Stephen E. Williams2 and William E. Magnusson 3
1. School of applied Science, Griffith University Gold Coast, Gold Coast Mail Centre, QLD 4217
2. Department Zoology and Tropical Ecology, James Cook University, Townsville QLD 4811 Australia.
3. Departamento de Ecologia, Instituto Nacional de Pesquisas da Amazonia - INPA. CP 478, 69011-970, Manaus, Amazonas, Brasil
Analysis of patterns in nature is a fundamental tool for studying the process of extinction. Herein, we demonstrate that the declining species of frogs from relatively undisturbed sites at high altitudes throughout eastern Australia, share a combination of ecological characteristics that distinguish them from non-declining species. Statistical analyses (logistic multiple-regression) demonstrate that declining species (species that have gone missing or whose populations have severely declined in recent years) have aquatic eggs and larvae that develop in the stream habitat, and small clutch size (low number of ovarian eggs/female). Non-declining species may share some but not all of these characteristics. Phyllogenetically independent analyses suggest that these characteristics are not clearly related to phylogeny at the generic or species level.
We suggest that the combination of these ecological characteristics makes some species more susceptible to population declines and extinction than others. These results (that declining frogs have a common set of ecological characteristics throughout eastern Australia) give some support to the hypothesis that the declines in amphibian populations are related to a single cause, and not due to a series of isolated events at the local scale. Furthermore this data suggests that the cause of the declines is in some way associated with the stream environment (pollution or pathogen ?) and those species with low fecundity are more susceptible than highly fecund species.
Harold Ehmann
PO Box 9, Blackwood SA 5051
The sustained high public profile of threatened frogs (and their enthusiastic and entertaining advocates) has captivated the community. Secondary school and public involvement in Frogwatch, Frogcensus and similar programs have met with exceptionally high community support for up to nine years. Frog and tadpole interest groups are active in all states, and more are forming. Frog weeks and frog days are now fixtures in calendars at the national and state level. Resources such as frog facts sheets, retailed tape recordings of frog calls, and information books and booklets have sustained strong community interest. Many community groups and individuals are involved in frog habitat rehabilitation and monitoring activities.
Many types of community groups are involved with frogs. These including frog and tadpole interest groups, landcare groups, recovery teams (which include people from professional and voluntary backgrounds), science teachers and conservation groups. Frog and tadpole interest groups have provided many of the resources for school talks and presentations, raised direct funding for declining frogs research, and mounted public displays at shows, fairs, pet expos and open days. They have assisted schools with wetlands habitat projects. Some are involved in frog survey work in an assisting capacity as well as on their own initiative.
The public's support and involvement can be better realised in three ways.
The Australian Frog Count (AFC) in more detail.
Tape recordings (hard data) are made by volunteers. The tapes may be provided by a corporate sponsor and sent out to participants who provide locality, time and collector contact details on the tape as a voice over. The tapes are centrally processed (listened to, scored for species and numbers heard, stored on CD-ROM for later rapid access and checking of uncertain or important calls, and a reply and report is sent to the volunteer). A data base is centrally maintained with ready access for participants to non-threatened species data. This system has already been prototyped (except for CD-ROM storage) by FATSG NSW (Inc) and is also used by the South Australian Environmental Protection Authority for its Frogcensus program.
The tape recordings can be processed by visually impaired people many of whom have acutely developed aural capabilities and keyboard skills. The visually impaired organisations have access to funding for appropriate training provided that it leads to employment.
Deborah Pergolotti
Cape York Herpetological Society, PO Box 2731, Cairns QLD 4870 and Tablelands Frog Club Inc. PMB 71 Yungaburra QLD 4872
As more and more issues - environmental and social - scream for attention and funding, the less money there is to go around. It has become a necessity for the community to be actively involved with wildlife conservation and recovery activities as governments and non government organisations can no longer fully meet the ever increasing demand for available resources. Amateur naturalists and interested citizens can make valid and useful contributions to the work of scientists.
For example, in Far North Queensland, volunteers are being used to undertake frog monitoring of declining species. This involvement came out of the community's concern over the cessation of 'official' monitoring after a change of government in Queensland. Experienced volunteers collect the desired data and train novices in work which does not require scientific expertise. There are other projects which the community can participate in such as collection of life history and juvenile development information, species location mapping and captive breeding. There are prerequisites, however, to the inclusion of volunteers: the first is sufficient funds for proper coordination and expenses; and the second is a legal mechanism to allow non professionals to participate within the limitations of existing legislation.
Jeremy Morante
NSW North Coast Frog Study Group, PO Box 61, Lismore NSW 2480, email: jmoran10@scu.edu.au
The recently formed community-based NSW North Coast Frog Study Group is working towards the ultimate goal of conserving Australia's unique frog species. Based in Lismore, in the beautiful northern rivers region of northern NSW, this group aims to increase the knowledge and appreciation of the rich frog fauna of the far north coast of NSW, assist in the preservation of the threatened frog species on the north coast of NSW and to foster an active interest in frogs in general.
One of the innovative new projects coming up for the NSW NCFSG is the Urban and Rural Frog Count Programs. These projects aim to document and assess the status of this regions' amphibians on privately owned lands and in the urban areas, mainly through field-based surveys. Surveys will be carried out during the period of most frog activity, October to March, in school holidays. Other planned events associated with these programs include the establishment of information stalls at local markets and the creation of a world-wide web (WWW) page so that everyone can freely access information about this regions' unique frog fauna.
Michael Mahony, John Clulow, Robert Browne, and Melissa Pomering.
Department of Biological Sciences, The University of Newcastle, Callaghan NSW 2308
The extent and pattern of declines and disappearances among Australian frogs has been covered in regional reviews and in several published papers. In the past ten years focus has switched to detection of the cause of declines, with the goal to prevent, control, and reverse the process. A number of candidates, with supporting field and laboratory evidence, have been postulated for the cause; UV-B radiation, a virulent pathogen, pollution, and stable synthetic hormonal antagonists in the atmosphere.
What could we do if any of these factors were identified as being widely responsible?
It is most unlikely that any of these could be mitigated in the short term.
If we accept this scenario, then Risk Assessment and Contingency Strategies must be a vital part of research and planning. We should keep in mind that it has taken 17 years, since the first disappearances occurred, to have narrowed the focus on potential causes, and in this time nine species have disappeared. Risk assessment requires a pro-active experimental approach to identifying which species are susceptible to decline, so that contingency means can be developed. The approach is to recognise that the frogs themselves are the sensitive end point and they should be exposed to determine susceptibility.
To prevent the total loss of species and genetic diversity among populations, a program of gene banking is desirable. Reproductive technologies provide powerful tools such as, methods for the non-intrusive collection of gametes using hormonal induction, in vitro fertilisation, and cryopreservation of gametes and possibly embryos.
Of course this approach is not a replacement to retaining species in functioning communities and ecosystems, however, it is vastly better for example than knowing that the entire subfamily Rheobatrachinae has vanished without any stored genetic material. These methods do not reduce the need to find the cause of declines, or to monitor populations, they are a contingency measure, a port of last resort to prevent the worst situation which is the total loss of unique evolutionary entities - species.
Gerry Marantelli
Amphibian Research Centre, PO Box 424 Brunswick Victoria 3056.
The need to utilise all available resources in the effort to stem amphibian declines has seen a certain amount of attention focused on husbandry and the use of captivity as a tool in the conservation process (e.g. Bloxam & Tonge 1995, Snyder et. al. 1995).
Numerous projects employing captive breeding or rearing to re-establish or bolster wild populations of frogs have been attempted with varying levels of success (e.g. Banks 1996, Tonge & Bloxam 1989). By their nature, conservation projects incorporating captive care achieve among the highest profiles of all conservation efforts. They place conservation actions within population centers and provide the public and media with easy access to otherwise 'invisible' species. Such access and exposure brings with it the opportunity to educate and influence as well as secure funds and resources not readily available to other less popularised or more remotely located conservation efforts. If not carefully handled this exposure may also lead to an unrealistically optimistic estimation of the true value of husbandry in such conservation projects.
Potential stakeholders in captive conservation represent a multitude of different interests and disciplines. The effective networking and correct utilisation of all such parties remains the only way to ensure the most beneficial outcomes from the use of husbandry in the conservation of Australia's anurans.
Banks C.B., 1996
A Conservation Program for the Threatened Romer's Tree Frog (Philautus romeri). Advances in Herpetoculture 1-5
Bloxam Q., Tonge S J., 1995
Amphibians: suitable candidates for breeding-release programmes. Biodiversity and Conservation 4 636-644
Tonge S., Bloxam Q., 1989
Breeding the Mallorcan midwife Toad Alytes muletensis in captivity. Int. Zoo Yb 28 45-53
Snyder N., Derrickson S., Beissinger S., Wiley J., Smith T., Toone W., Miller B., 1995
Limitations of Captive Breeding in Endangered Species Recovery. Conservation Biology 10(2) 338-348
RK Browne, J Clulow and M Mahony
Dept of Biological Sciences, The University of Newcastle, NSW 2308
In the future, captive breeding programs are likely to become increasingly important in the management of endangered amphibian species. Such programs are likely to be a source of animals to guard against extinction in the wild, and also to supply animals for repopulating areas which have lost or experienced substantial reductions in populations. One imperative on such programmes will be a requirement to be as cost effective and efficient as possible with the husbandry procedures employed. Bearing this in mind, we have conducted a preliminary study using eggs and tadpoles from the spotted grass frog, Limnodynastes tasmaniensis, to determine whether it is feasible to raise tadpoles to metamorphosis at very high densities. The fundamental strategy utilised a regime of high water exchange rate (to prevent build-up of toxic metabolic products) and saturated feeding. The results of the preliminary trial are very promising, with densities of tadpoles as high as 52 per litre achieving metamorphosis in 4 weeks (at 20-25o C), whilst maintaining high growth rates with no mortality in metamorphs (high density treatment growth rates were as high as low density controls). The results suggest that many of the approaches employed in fish aquaculture should be successfully applied to intensive husbandry of endangered amphibians.
J Clulow, RK Browne, M Pomering & M Mahony
Dept of Biological Sciences, The University of Newcastle, NSW 2308
The decline of amphibian species occurring over the last two decades is a problem unique in the history of conservation biology in that no cause has been established for the decline of most of the species involved. Consequently, no means of reversing declines or preventing the onset of new declines exists. Even if current research being undertaken on causes of amphibian decline is successful, it is highly likely that no effective means of reversing such processes in the natural environment of the affected species will be available (eg if the causal agent is UV light, or a viral epidemic). Consequently, new approaches to the problem of amphibian conservation need to be investigated if further species extinctions are to be prevented.
Cryopreservation of amphibian gametes (sperm and eggs) and embryos, and captive husbandry offer exciting possibilities for establishing "insurance" against species extinction in the case of complete loss of field populations. Recent advances in our laboratory have established that spermatozoa from a number of native amphibian species can be successfully frozen and thawed, with retention of motility and fertilising capacity. As well, we have shown that sperm can be collected in the urine of male frogs and successfully frozen, removing the necessity to kill males for sperm collection. Future research in our laboratory will investigate the feasibility of cryopreserving amphibian eggs and embryos.
Frank Lemckert
Forest Research and Development Division, State Forests of NSW PO Box 100 Beecroft, NSW 2119
The hip-pocket frog (Assai darlington) breeds in the leaf litter of rainforests and wet sclerophyll forests of northern NSW and southern Queensland. Surveys for this frog have continued in the Dorrigo area since 1993 with eight populations having been located. Seven of these populations were found within old growth forest, with the eighth being found in forest logged the previous year. In 1994 an uncontrolled wildfire destroyed the "logged population" and back-burning severely reduced another.
These results suggest that this frog is sensitive of disturbance, however the species remains common in logged areas in more northern parts of its range. Individuals in the Dorrigo area may be less able to cope with disturbance because they are at the southern limit of the species' range and so at the extremes of their physiological tolerance. This has implications when considering the conservation of other rare species.
B. Lewis and R. Goldingay
School of Resource Science and Management, Southern Cross University, Lismore, NSW 2480
The green and golden bell frog, Litoria aurea has declined dramatically in NSW over the last 20 years and it is now listed as endangered. Historically its distribution in NSW extended from the Victorian border to as far north as Byron Bay. In order to adequately secure this species it is important to conserve populations throughout its historic range.
The first step is to conduct detailed surveys to determine its current distribution and abundance. The extent to which this has been done varies throughout NSW. The aim of this study was to conduct detailed surveys for this bell frog within its historic range in north-eastern NSW, north of Coffs Harbour. There were six historic sites within our study area. We identified one further site record from discussions with local zoologists. We surveyed each of these sites and seven additional sites containing potential habitat during 1996 and 1997. Each site was visited during the day and at night, and most sites were surveyed on at least five separate occasions. Bell frogs were detected at only two of these sites, both within Yuraygir National Park where they have been recorded during the last three years and both within dispersal distance of each other.
Despite extended surveys, the total number of frogs recorded was less than 10. This confirms earlier records of a small population of bell frogs in Yuraygir. We also conducted surveys for the mosquito fish across all sites and found that it was present at low density at virtually all sites except those in Yuraygir. There are several conclusions from this study: i) the demise of the bell frog in this region may be due to habitat destruction, the presence of the cane toad and the mosquito fish, ii) there appears to be only one population remaining in northern NSW and, iii) the remaining population is anything but secure, despite being located within a National Park. We recommend that a management plan is urgently needed for the bell frogs in Yuraygir and that further surveys be conducted over the next two years to verify that only one population remains.
Karen Thumm and Michael Mahony
Department of Biological Sciences, The University of Newcastle, Callaghan NSW 2308
The Red-Crowned Toadlet (Pseudophryne australis), is a vulnerable species which is restricted to the Sandstone Basin around Sydney. Urbanisation is leading to the destruction and degradation of its habitat. Although the reason for the loss of populations appears evident, there is no room for complacency, as unexplained declines have been documented for other congeners (e.g. P. corroboree and P. bibroni).
After detailed field examination and habitat analysis of over 55 extant and former sites, we conclude that Pseudophryne australis is an ecological specialist, breeding typically below the first sandstone escarpment in ephemeral first-order drainage lines.
Reproductive losses are high with a large proportion of the terrestrial egg masses and tadpoles drying up before replenishing rain falls. Houses in Sydney are generally built on top of sandstone ridges. There is immediate destruction of habitat as well as the indirect degradation of habitat by stormwater pollution, changes to hydrology, removal of bushrock for landscaping, clearing for fuel set-back zones, and frequent fire hazard reduction burns.
In order to assess the sensitivity of the species to various and cumulative human impacts, data on the reproductive output of field populations and of individual captive females is being studied. Specific studies are being carried out on the plasticity observed in clutch size, ovum diameter, embryonic behaviour and weights at metamorphosis as well as the relationship between inter-clutch interval and clutch size. In order to remove the threats to this species and to develop and implement conservation management procedures it is vital to understand its reproductive ecology and its population demography.
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