NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Northern Corroboree Frog Pseudophryne pengilleyi Wells & Wellington, 1985 (family Myobatrachidae) is a small endemic Australian frog, with adults reaching a length of between 2.5 to 3 cm. The species has a distinctive dorsal colouring of greenish-yellow with shiny black stripes that are frequently broken and interconnected (Pengilley 1966; Cogger 1992). This pattern extends over the limbs and flanks. The underside is marbled with black and white, or black and yellow. A large flat femoral gland is present on each hind limb and the inner metatarsal tubercle is low, round and not shovel-shaped. The inner toe has a single phalanx.
2. Two species of corroboree frog are known in Australia; the southern, Pseudophryne corroboree and the northern. The two species are distinguished by differences in range, colour-pattern, morphology and call (Pengilley 1966; Osborne et al. 1996), skin biochemistry (Daly et al. 1990) and genetics (Roberts & Maxson 1989; Osborne & Norman 1991; Morgan et al. 2008). The lime-yellow, narrow broken pattern of stripes of the Northern Corroboree Frog distinguishes it from the Southern Corroboree Frog (P. corroboree) which is brighter yellow and has a broader unbroken striped dorsal pattern (Osborne 1991). In addition, P. pengilleyi has a smaller body and tibia length than P. corroboree (Osborne et al. 1996).
3. The Northern Corroboree Frog has a highly restricted distribution, occurring only in the high montane and sub-alpine bog environments in the northern Australian Alps of NSW and high country around the ACT. The species is known from sites within three disjunct geographic areas in NSW which represent three subpopulations: Fiery Range, southern Brindabella Range and northern Brindabella Range (Morgan et al. 2008; D. Hunter pers. comm. 2009).
4. The Northern Corroboree Frog is a habitat specialist, utilising two distinct habitat types throughout its life cycle: a breeding habitat associated with pools and seepages in sphagnum bogs, wet tussock grasslands and wet heath, and a terrestrial non-breeding habitat in forest, sub-alpine woodland and tall heath, usually within 10-30 m of the breeding area (D. Hunter pers. comm. 2010). The Northern Corroboree Frog feeds mostly on small ants, and to a lesser extent, other invertebrates (Pengilley 1971b; Osborne 1990).
5. The overall geographic range of the species is highly restricted. In NSW, the extent of occurrence (EOO) is estimated to be less than 2 000 km2 and the area of occupancy (AOO) is less than 340 km2 (based on 2 x 2 km grid cells, the scale recommended by IUCN (2008) for assessing AOO).
6. Breeding in the Northern Corroboree Frog occurs from January to March (Pengilley 1966; 1971a; 1973). Females deposit 16 to 38 eggs in nests occupied by breeding males. Tadpoles develop within the egg capsule and hatching occurs at four to six months through autumn and winter, during periods of high rainfall or snowmelt. Tadpoles move out of the nest site and into an adjacent pool before undergoing metamorphosis in early summer (Pengilley 1966; 1973; Hunter et al. 1999). As they grow larger, the juveniles leave the breeding area and move into the adjacent non-breeding habitat where they are thought to remain until adulthood.
7. The majority of male Northern Corroboree Frogs will reproduce four years after metamorphosis (Hunter 2000). In the lower altitude sites (northern Brindabellas and Fiery Range) females also reproduce four years after metamorphosis, however in the high altitude sites (southern Brindabellas) females take an additional year to mature (D. Hunter pers. comm. 2009). Annual survivorship estimates for the adult life stage are restricted to information on breeding males as limited information is available for females (Hunter 2000). Maximum age is likely to be 10 years (D. Hunter pers. comm. 2009); however, average longevity is around six years (D. Hunter pers. comm. 2009). Annual survivorship for adult males is between 50% and 60% (Hunter 2000). ‘Generation length’ (IUCN 2008) is estimated to be five to seven years.
8. Based on the number of calling males recorded in surveys undertaken in 2008 and the number of eggs in nests, the total number of mature individuals of the Northern Corroboree Frog in NSW is estimated to be between 2 000 and 3 000 (D. Hunter & R. Pietsch pers. comm. 2009).
9. Populations of the Northern Corroboree Frog in NSW have experienced significant decline in recent years. For example, in 1988 the number of adult males in the Brindabella Ranges (northern and southern subpopulations combined) was estimated to be 2 000-3 000 (Osborne 1988), yet in 2009 just 25-75 adult males were thought to be present (D. Hunter & R. Pietsch pers. comm. 2009). This represents a decline of between 96 and 99% over 21 years (or three generations). Similarly, tens of thousands of adult males were believed to be in the Fiery Range subpopulation in 1988 (Osborne 1988), and although this estimate is very broad, assuming a minimum historic population of 10 000 males and based on the 2009 estimate of between 1 000 – 1 400 males (D. Hunter & R. Pietsch pers. comm. 2009), this subpopulation has experienced a decline of between 86 and 90%. In addition, many of the previously known breeding sites in the Brindabella Ranges no longer contain the species, or contain extremely low numbers of individuals (Hunter et al. 2006). The vulnerability of the Brindabella subpopulations is increased by the linear nature of the area occupied by the frogs, which restricts migration between breeding sites within the subpopulation.
10. Genetic studies indicate there is highly restricted gene flow between the known subpopulations of the Northern Corroboree Frog (Morgan et al. 2008), probably as a result of physical barriers restricting movement (e.g. the Goodradigbee River valley and the Coolamine plains) and the reduction of suitable habitat between subpopulations. Several breeding sites of the species have been destroyed or damaged (Osborne 1988; 1991) with annual monitoring suggesting an estimated 50% of sites are now ‘lost’ across the species’ range (D. Hunter & R. Pietsch pers. comm. 2009). As a result, there is evidence that subpopulations of this species are now severely fragmented.
11. The major cause of decline in the Northern Corroboree Frog over the last three decades is believed to be the introduced Amphibian Chytrid Fungus (Batridiochytrum dendrobatoides) (Berger et al. 1999; Hunter et al. 2006). Initial decline of this species coincided with the first appearance of chytrid in the population during the early 1990s (Hunter unpublished data). ‘Infection of frogs by amphibian chytrid causing the disease chytridiomycosis’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.
12. As the Northern Corroboree Frog occurs in a narrow climatic range (the sub-alpine and alpine regions of eastern Australia), any climate change is also likely to have a serious impact on this species (Bennett et al. 1991). Potential impacts include; altering the timing of breeding so that egg and tadpole development occur earlier or later than is optimal, influencing the hydrology of breeding pools, and affecting the growth and dynamics of vegetation in the breeding habitat. ‘Anthropogenic Climate Change’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.
13. Feral Pigs (Sus scrofa) and Horses (Equus equus) damage both the over-wintering and breeding habitats of the Northern Corroboree Frog (DECC 2007). Trampling by wild horses has caused considerable disturbance to breeding sites in the Fiery Range (DECC 2007). Feral Pigs can cause extensive damage to the vegetation and soil in frog breeding areas (Alexiou 1983), and when used as wallows can cause considerable damage to ponds containing tadpoles (Helman et al. 1988). ‘Predation, habitat degradation, competition and disease transmission by Feral Pigs Sus scrofa Linnaeus 1758’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.
14. Fire is also likely to affect the Northern Corroboree Frog through direct mortality of individuals and from longer-term impacts resulting from habitat alteration. Regular burning of understorey litter and grass cover in woodland and heath habitats may reduce available shelter, making the Northern Corroboree Frog more susceptible to predation, dehydration or freezing during winter (Osborne 1991). ‘High frequency fire resulting in the disruption of life cycle processes in plants and animals and loss of vegetation structure and composition’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995.
15. Invasive exotic plant species occur at a number of Northern Corroboree Frog breeding sites in the Fiery Range and Northern Brindabella Range subpopulations (Osborne 1990; NSW NPWS 2001). The two species considered most detrimental to the frogs are Rubus fruticosus (Blackberry) and Mimulus moschatus (Monkey Musk), which can cover large areas of Northern Corroboree Frog breeding habitat.
16. The Northern Corroboree Frog is listed as a Vulnerable species under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and as Endangered in the Australian Capital Territory (ACT) under the Nature Conservation Act 1980.
17. The Northern Corroboree Frog Pseudophryne pengilleyi Wells & Wellington, 1985 is eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, it is facing a very high risk of extinction in New South Wales in the near future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2010:
Clause 6 Reduction in population size of species
The species has undergone, is observed, estimated, inferred or reasonably suspected to have undergone or is likely to undergo within a time frame appropriate to the life cycle and habitat characteristics of the taxon:
(a) a very large reduction in population size,
based on:
(a) an index of abundance appropriate to the taxon.
Dr Richard Major
Chairperson
Scientific Committee
Proposed Gazettal date: 17/12/10
Exhibition period: 17/12/10 – 11/02/11
References:
Alexiou PN (1983) Effect of feral pigs (Sus scrofa) on subalpine vegetation at Smokers Gap, ACT. Proceedings of the Ecological Society of Australia 12, 35-142.Bennett S, Brereton R, Mansergh I, Berwick. S, Sandford K, Wellington C (1991) ‘The Potential effect of the Enhanced Greenhouse Climate Change on Selected Victorian Fauna’. Arthur Rylah Institute for Environmental Research, Heidelberg.
Berger L, Speare R, Hyatt A (1999) Chytrid Fungi and Amphibian Declines: Overview, Implications and Future Directions. In ‘Declines and Disappearances of Australian Frogs’. (Ed. A Campbell) pp. 23-33. (Environment Australia: Canberra)
Cogger HG (1992) ‘Reptiles and Amphibians of Australia.’ (AW Reed: Sydney)
Daly JW, Garraffo HM, Pannell LK, Spande TF, Severini C, Erspamer V (1990) Alkaloids from Australian frogs (Myobatrachidae): Pseudophrynines and pumiliotoxins. Journal of Natural Products. 53, 407- 421.
DECC (2007) ‘Draft NSW and National Recovery Plan for the Southern Corroboree Frog Pseudophryne corroboree’. DECC, Queanbeyan, NSW.
Helman CE, Gilmour PM, Osborne WS, Green K (1988) ‘An ecological survey of the Upper Cotter Catchment, ACT.’ Report to the Conservation Council of the South-eastern Region and Canberra.
Hunter D (2000) Population demography and conservation of the Southern Corroboree Frog. Master of Applied Science Thesis, University of Canberra.
Hunter D, Osborne W, Marantelli G, Green K (1999) Implementation of a population augmentation project for remnant populations of the Southern Corroboree Frog (Pseudophryne corroboree). In ‘Declines and Disappearances of Australian Frogs’. (Ed. A Campbell) pp. 158-167. (Environment Australia: Canberra)
Hunter D, Pietsch R, Marentelli G (2006) ‘Recovery actions for the southern and northern corroboree frogs (Pseudophryne corroboree and Pseudophryne pengilleyi): Annual report and recommendations’. Unpublished report to the Department of Environment and Climate Change.
IUCN (2010) ‘Guidelines for using the IUCN Red List Categories and Criteria. Version 8.0.’ (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland).
Morgan MJ, Hunter D, Pietsch R, Osborne W, Keogh JS (2008) Assessment of genetic diversity in the critically endangered Australian corroboree frogs, Pseudophryne corroboree and Pseudophryne pengilleyi, identifies four evolutionarily significant units for conservation. Molecular Ecology 17, 3448–3463.
NSW NPWS (2001) ‘Approved Recovery Plan for the Southern Corroboree Frog (Pseudophryne corroboree).’ NSW NPWS, Hurstville NSW.
Osborne WS (1988) ‘A survey of the distribution and habitats of Corroboree Frogs, Pseudophryne corroboree in Kosciusko National Park: with a reference to ski resort development’. Report prepared for NSW NPWS.
Osborne WS (1990) The conservation biology of Pseudophryne corroboree Moore (Anura: Myobatrachidae): a study of insular populations. Ph.D. thesis, Australian National University, Canberra.
Osborne WS (1991) ‘The biology and management of the Corroboree Frog (Pseudophryne corroboree) in NSW.’ NSW NPWS, Species Management Report Number 8, Sydney.
Osborne WS, Norman JA (1991) Conservation genetics of Corroboree Frogs, Pseudophryne corroboree: population subdivision and genetic divergence. Australian Journal of Zoology 39, 285-297.
Osborne WS, Zentelis RA, Lau M (1996) Geographical variation in Corroboree Frogs, Pseudophryne corroboree Moore (Anura: Myobatrachidae): A reappraisal supports recognition of P. pengilleyi Wells and Wellington. Australian Journal of Zoology 44, 569-587.
Pengilley RK (1966) The biology of the genus Pseudophryne (Anura: Leptodactylidae). M.Sc. thesis, Australian National University, Canberra.
Pengilley RK (1971a) Calling and associated behaviour of some species of Pseudophryne (Anura: Leptodactylidae). Journal of Zoology 163, 73-92.
Pengilley RK (1971b) The food of some Australian anurans (Amphibia). Journal of Zoology 163, 93-103.
Pengilley RK (1973) Breeding biology of some species of Pseudophryne (Anura: Leptodactylidae) of the Southern Highlands, New South Wales. Australian Zoologist 18, 15-30.
Roberts JD, Maxson LR (1989) A molecular perspective on the relationships of Australian Pseudophryne (Anura: Myobatrachidae). Systematic Zoology 38, 154-165.
Wells RW, Wellington CR (1985) A classification of the Amphibia and Reptilia of Australia. Australian Journal of Herpetology Supplement Series 1, 1-61.