Publications
NSW National Parks and Wildlife Service, July 2001
ISBN 0 731 36213 6
The recovery objectives, actions and criteria listed below are based on the need for determining the cause of the ongoing population decline in the Southern Corroboree Frog. The approach taken is both experimental and proactive; the general philosophy follows that of Caughley and Gunn (1996). Caughley and Gunn state that "the effectiveness of treating a decline depends on the accuracy with which its causes have been diagnosed. More than one factor may be driving a decline which increases the need for an experimental investigation. A shotgun approach with a suite of recovery treatments is seldom, if ever, the answer. Diagnosis will reveal the magnitude of how different factors are affecting the decline and that, in turn, will guide priorities for the treatments". Once such a diagnosis has been made, management actions additional to the general management prescriptions proposed for populations in Kosciuszko National Park by Osborne (1991) can be implemented. These may include, for example, artificial maintenance of breeding pools or deliberate flooding of oviposition sites to reduce mortality in the early life-history stages.
In the long term, the overall objective of the recovery program is to downlist the species from critically-endangered to endangered within ten years (based on IUCN criteria of population size and trends, extent of occurrence and probability of extinction). The immediate objective is to prevent the continuing decline in population numbers and through experimental management increase the size of selected representative populations across the geographic range of the species.
Populations of Southern Corroboree Frog stop decreasing and remain stable or increase directly due to recovery actions at six key sites over five years.
The design will include the following treatments: altitude, precipitation, pool abundance, catchment size, original population size, breeding habitat, non-breeding habitat and metapopulation position. Monitoring will include tadpoles to determine whether breeding has been successful.
Population monitoring is an important component of the recovery process for threatened frogs in Australia (Tyler 1997). However, a lack of long-term studies has hampered efforts to determine the full extent of decline in amphibian populations, and the question as to whether population declines are indicative of a population collapse, or simply part of longer-term fluctuations in response to local weather patterns, or some other cyclical phenomena remains unresolved for many species (Pechmann et al. 1991; Pechmann and Wilbur 1998).
Implementation of an effective program to monitor representative populations, including known extinction sites, for twenty years.
Research will be undertaken to identify the most sensitive period of the life-history. This research is essential for the undertaking of any form of population viability estimation, and will include determining at what stage the highest mortality is experienced. Research initially will focus on the pre-metamorphic stage (eggs, tadpoles) because this is the stage that usually suffers the highest levels of mortality through predation, competition and pond-drying (Wilbur 1980; Duellman and Trueb 1986).
Because of the already seriously depleted size of most local populations of the Southern Corroboree Frog, studies of embryonic and tadpole mortality will have to be undertaken somewhat opportunistically. To reduce disturbance to egg clutches, embryonic mortality will be assessed only in conjunction with the collection of eggs to be used in recruitment enhancement research (see Action 2.1). Similarly, tadpole mortality studies will be undertaken at the recruitment enhancement sites. This will involve partitioning sections of each experimental pool (chosen randomly) in order to allow for an accurate census. Since the aim of the population enhancement project is to reduce early life history mortality the use of enclosures is desirable because tadpoles can be easily gathered and moved to safer waters if the pools start drying. It will also allow for a direct comparison of survival rates of field-hatched tadpoles compared to tadpoles hatched in the laboratory and maintained over winter (Action 1.3) . Embryonic mortality will be determined by checking randomly located egg masses just prior to hatching.
Research completed which determined which life-history stage is contributing most to the current demographic failure and decline.
It will be almost impossible to undertake direct research on juvenile frogs and adults in the field because of their small size (difficult to fit transmitters or other electronic marking devices) and because they are likely to disperse into extensive areas of thick heath and woodland where there is little likelihood of finding individuals.
Although it may be difficult to undertake direct studies of survivorship in juveniles and adults it will be possible to compare the age structure of breeding adults present in the populations now with samples of adults collected and preserved in museums prior to the decline. In recently completed preliminary research funded by the University of Canberra, D. Hunter successfully examined the age structure of adult breeding males of Northern Corroboree Frogs from a number of low altitude and high altitude sites. Individual males were toe-clipped to obtain bone material for ageing, and their throat pattern was sketched for individual identification. Other data collected included sex, weight, snout-urostyle length, tibia length, whether the males had been successful in mating, and the number of eggs in nest sites. Information was also obtained on the effect of disturbing males in their nest site.
Information on the age structure of the adult breeding population obtained.
Serious declines affecting many species of frogs have occurred at high altitudes in undisturbed mountain environments (eg. Crump et al. 1992; Carey 1993; Fellers and Drost 1993; Kagarise, Sherman and Morton 1993; Gillespie et al. 1995). The global distribution of declines in such habitats suggests causal agents that exert their influence on a global scale. One plausible explanation for the declines is that exposed tadpoles or eggs are being damaged by UV-B radiation as a result of ozone layer depletion (Blaustein et al. 1994). High elevation regions have experienced the greatest increase in solar Ultraviolet-B (UV-B) radiation (Herman and Larko 1994) and for this reason the potential effects of UV-B on the survival of the Southern Corroboree Frog will be investigated.
Field experiments determining the sensitivity of eggs, embryos and tadpoles of the Southern Corroboree Frog to ambient ultraviolet radiation completed.
The premise behind this action is that the high egg and tadpole mortality observed during the over-winter phase is significantly contributing to the current regulation of population size. The first phase of this action is to investigate possible techniques which may be used to increase over-winter survival. The second phase will involve monitoring the number of breeding males between mortality-reduced populations and control populations to investigate the potential for this procedure to increase the breeding adult population size.
Two possible techniques for reducing over-winter mortality are currently being tested. The first involves removing eggs from nest sites during autumn, rearing them in captivity through to an early stage tadpole at the Amphibian Research Centre (ARC), and returning them to their natal pools in early spring after snow melt. During the 1997, 1998 and 1999 breeding seasons, a comparison between levels of field survivorship and captive reared survivorship through to metamorphosis was undertaken. The results showed that the process of captive rearing significantly increases survivorship though to metamorphosis (for details of the methodology and results refer to Hunter et al. in press).
The second technique being investigated involves removing the eggs from the nest sites during autumn, after the breeding pools have filled with water, and placing them directly into the pools. Preliminary results suggest that this technique may also be used successfully to reduce early life-history mortality. An investigation will be undertaken in 2000-2001 to compare survivorship of field control, captive reared individuals and eggs placed directly into the water. This will allow the choice of the most appropriate technique for incorporation into this project.
Action 2.1 was initiated in 1997 with survivorship through to metamorphosis being increased in three remnant populations. An additional four populations were incorporated into the project during 1998 and 1999 to make a total of seven populations where recruitment enhancement is being undertaken. Since the Southern Corroboree Frog takes three years to reach reproductive maturity from the egg stage, it will probably not be until January 2002 before we will have any indication as to the success of this project. Furthermore, given that the Southern Corroboree Frog may live for up to six years as a breeding adult, successive years of recruitment enhancement may provide more conclusive results due to the cumulative effect on the breeding population size. Further populations may be incorporated into the project if the initial results prove successful.
Further decline in population numbers at sites with extant populations has been prevented through active management of eggs and tadpoles in the field.
Because of the major collapse of the wild population, development of a captive breeding program for the Southern Corroboree Frog is now an essential component of the recovery program. The aim of this breeding program is to provide a source of animals for future experimentation and reintroduction projects, secure the genetic diversity of the species in the event of further population declines and extinctions and provide an educational resource and focus for fund raising efforts. The initial phase of this program will involve developing adequate captive husbandry techniques for this species. The ultimate timing and scale of this program will be largely determined by the success of this initial phase.
Captive husbandry research commenced in 1997. The NPWS contracted the ARC in Melbourne to undertake private research on methods for maintaining and breeding both the Northern and Southern Corroboree Frogs in captivity. A small number of adult Northern Corroboree Frogs have been maintained in captivity for two years however breeding has not been achieved at this stage. Similarly, a small number of Southern Corroboree Frog tadpoles, which were obtained from the population enhancement program (refer to Action 2.1) during 1997, 1998 and 1999, have been successfully reared over the last three years. Because they have not yet attained reproductive maturity, their breeding potential cannot be assessed. Additional tadpoles of the Southern Corroboree Frog and adults of the Northern Corroboree Frog will be supplied to the ARC during 2000 and 2001 for further development of this program.
At present the captive husbandry program is being conducted exclusively at the Amphibian Research Centre. Because of the possibility, however remote, that a single captive population could be destroyed by accident or become infected by a pathogen, a second captive colony would be highly desirable. This possibility will be considered by the Recovery Team subject to the availability of necessary funding and sufficient numbers of captive animals from the initial captive breeding program to make it feasible.
An increase in population numbers at sites targeted for recruitment enhancement through the captive husbandry program is achieved.
While the effect of disease on amphibian populations is poorly known, the possibility that a disease is affecting the populations of Southern Corroboree Frog should not be ignored. Moreover, given recent concern about a particularly virulent fungal disease affecting captive frogs (Lee Berger, personal communication), the risk of introducing a disease into wild populations from captive-reared animals should be considered. Returning captive-reared animals to extant populations is considered to be highly undesirable due to the risk of introducing a disease into the population.
A prudent approach, with regard to avoiding disease transmission, would involve the screening of all individuals just prior to their release (Dodd and Seigel 1991). Therefore, a sample of both field and captive tadpoles will be tested for pathogens before the release of the captive population back into the wild.
One additional action that will be considered in the future is determining whether the chytrid fungus is currently present in the wild population.
A screening program designed and implemented for the presence of pathogens in field and captive reared Southern Corroboree Frogs returned to field populations.
The specific breeding habitat requirements of Corroboree Frogs have been studied in detail by Osborne (1990). The main feature of the breeding habitat is the presence of shallow pools or seepages, which occur in open areas away from trees or large over-hanging shrubs. Because of the lengthy (6+ months) larval period of the frogs, the water bodies used as tadpole development sites necessarily must be of long duration. Osborne (1990) also found that the frogs prefer large, shallow pools which warm during the day and have an edge protected by moss and other vegetation that provides suitable calling and oviposition sites. As previously mentioned some ecologists suggest that, following the removal of grazing and associated disturbance, wetlands have undergone seral changes (generally interpreted as a form of recovery), however the hydrology of the breeding habitat and the range of pools available for breeding may differ in some unknown manner from the pre-European condition (I. Pulsford pers. comm.). Whilst we suggest that it is highly unlikely that the current decline has been brought about by these changes (in some locations the frogs have declined or completely disappeared from numerous sites with large numbers of pools present; Hunter and Osborne in prep.), it is prudent to attempt some form of habitat manipulation to test this hypothesis. This research could also be done in association with a translocation program should tadpoles be available in the future. Before any habitat manipulation was initiated, chosen sites would be checked for possible presence of Carex raleighii (which commonly grows in Sphagnum areas) and other threatened species.
Using an experimental design (yet to be determined but including unmanipulated control sites and manipulated experimental sites), pools will be created or modified to provide additional potential breeding habitat at selected sites. In the former instance habitat manipulation will involve the construction of artificial pools of different sizes. In the latter the provision of artificial depressions in existing pools to provide refugia for tadpoles as the pools dry out. This manipulation would only take place close to extant populations.
If suitable numbers of tadpoles are available for translocation, an attempt will be made to re-establish the Southern Corroboree Frog at a suitable site or sites, or an attempt will be made to increase the population size of breeding adults at existing experimental sites. Careful monitoring will be required to determine the success of such habitat manipulation. A research plan and appropriate experimental design will be prepared for this proposal in the near future.
Successful completion of experimental population translocation to known extinction sites in conjunction with habitat enhancement (eg. pool construction) and maintenance of suitable hydrological conditions.
The main Actions undertaken by NPWS are described below. Many of these Actions are undertaken routinely during normal park management activities and have not been costed in this Recovery Plan.
All known Southern Corroboree Frog breeding sites in Kosciuszko National Park will be given full protection from direct human disturbance. In particular, the larger remaining breeding sites in the Dargals Range, Ogilvies Creek, Jagumba Range and Round Mountain region will be accorded a very high priority. Sites in this region represent the only remaining substantial breeding aggregations that still maintain some semblance of a metapopulation structure. Because of the possible attraction of the frogs to tourists, or other potential collectors, the exact location of breeding sites in this region will not be made public. The present classification of the frogs as 'Significant Natural Features' (NPWS 1984a) will remain, and will help with the protection of potential breeding sites in the resort areas and elsewhere.
The Kosciuszko National Park Plan of Management currently provides for the exclusion of fuel reduction burning from Southern Corroboree Frog breeding and non-breeding habitat (NPWS 1984b). Every effort should also be made to protect these areas from wildfire.
Southern Corroboree Frogs are completely dependent on continued water seepage into the shallow breeding pools. During the lengthy (approximately six-month) period that the tadpoles are developing they are vulnerable to mortality if the pools dry. Consequently any activity that reduces water flow into the breeding habitat is potentially detrimental to the continued existence of the frogs at the site. Activities in the catchments of the breeding sites which may be deleterious include road construction, the laying of surface and sub-surface drains, cables and sewerage mains and the construction of aqueducts. Such activities, which may intercept and reduce water flow into breeding sites, are not compatible with the protection of the breeding habitat.
Vehicle use and excessive human trampling within the breeding habitat is likely to damage both the pools and the moss used as breeding sites by the frogs. Such activities will be prevented in order to protect the breeding pools, drainage lines and seepages.
At the end of the breeding period adult and sub-adult frogs disperse up to 300 metres or more from the breeding pools (Osborne 1988). Most individuals leave the moist breeding habitat and spend winter in the woodland and drier heathland that surrounds the breeding sites. In these areas some frogs hibernate beneath logs but most probably shelter beneath a ground layer cover of litter, grass and other vegetation. The frogs can be expected to occur in these drier non-breeding season habitats during much of the period from May to December when the soil in these areas is relatively moist from autumn and winter rains.
Although Corroboree Frog non-breeding habitat is dispersed and extensive, when compared to the breeding areas, large scale disturbance from activities such as land clearing and burning would be potentially damaging to the frogs. Clearing of vegetation, and in particular burning of the understorey litter and grass cover, would reduce the shelter available to the frogs and make them more vulnerable to dehydration during dry weather. Because prescribed burning (control or fuel reduction burning) has the specific purpose of greatly reducing ground litter cover, and because the burns are usually carried out in autumn when the frogs have moved into woodland and heath, such programs will not be implemented near Southern Corroboree Frog breeding sites (see earlier section on protection of breeding sites).
Apart from the NSW National Parks and Wildlife Service, a number of other organisations and authorities operate facilities in Kosciuszko National Park (details listed in National Parks and Wildlife Service 1984b). In particular, the Snowy Mountains Hydro-Electric Authority has responsibilities that may affect the conservation of Corroboree Frogs. A number of Southern Corroboree Frog breeding sites occur near aqueducts and roads maintained by Snowy Mountains Hydro-Electricity Authority. Although the existing usage of these areas is unlikely to further damage frog breeding sites, any major new construction in areas frequented by the frogs may adversely affect their breeding habitat and would require full assessment of potential impacts.
Disturbance to vegetation and soil from pig rooting by Feral Pigs (Sus scrofa) in some areas can be extensive, and pools containing Corroboree Frog tadpoles are sometimes used as wallows by the pigs. Although the frogs may on occasions breed in small pools caused by pig disturbance, the overall impact on Corroboree Frogs is considered to be harmful. In keeping with the general policy of KNP on feral animal control, pig numbers will be monitored and controlled in areas known to have Southern Corroboree Frogs.
Habitat management prescriptions are implemented, including high priority management protocols to prevent disturbance to remaining occupied breeding sites and adjacent non-breeding habitat; through management actions, protection of sites from fire, vehicle disturbance and the activities of pest animals, particularly pigs.
Extension and media activities will be continued and targeted at educating teachers, bushwalkers, skiers, campers and the public about the precarious situation of the frog and the importance of the recovery program. Interpretive signs or similar material will be placed at sites where visually conspicuous recovery actions are taking place near areas visited by walkers or other users (eg. at breeding sites where pools have been modified or constructed).
Training will be provided for management, field and planning staff (NPWS, SMHEA, ski resorts, etc.) to promote an understanding of the ecology and monitoring of the Southern Corroboree Frog, and ensure compliance with protection of breeding and non-breeding habitat. NPWS staff, community groups and tertiary students will be involved in the monitoring.
Support from conservation organisations and industry in the form of financial and other assistance to the recovery program will be sought.
Community information brochures, interpretation signs, and informative articles prepared and representatives of relevant authorities trained to assist with appropriate research and management activities.
A Recovery Team has been in existence since 1995. The Recovery Team includes participants with the range of skills necessary for determining recovery actions and for setting priorities associated with recovery research and management. Expertise on the Recovery Team includes amphibian biology and ecology, amphibian husbandry, wildlife management, national park management, human resources and project development and financial management.
The Recovery Team will be responsible for implementing the Recovery Plan, including the detailed planning required for the program, such as the identification of actions, targets, responsibilities and time-lines for completion. The Recovery Team will also monitor and assess implementation of the Recovery Plan, and will carry out administrative tasks relating the recovery effort, including preparing contracts for the components of the program, and obtaining relevant permits to enable work to proceed. The major cost for management of the recovery program will be met by NPWS. Other participating agencies will be responsible for their own costs.
The Recovery Team continues to operate and recovery actions continue to the implemented.
