6 Frog Declines and Associated Management Response in South-Eastern Mainland Australia and Tasmania
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6 Frog declines and associated management response in south-eastern mainland Australia and Tasmania David Hunter, Nick Clemann, David Coote, Graeme Gillespie, Greg Hollis, Ben Scheele, Annie Philips, and Matt West INTRODUCTION the species appear to be in imminent risk of extinction Within south-eastern Australia there are 19 species of (Skerratt et al. 2016). frogs currently listed as threatened at a national level This chapter summarises current knowledge of the under the Commonwealth (federal) Environment Protec- conservation status, management responses, and future tion and Biodiversity Conservation Act 1999 (EPBC Act), directions for conservation of frogs in the temperate areas and/or at a state level under the Victorian Flora and of south-eastern mainland Australia and Tasmania. Fauna Guarantee Act 1988 (FFG Act), the New South Wales Threatened Species Conservation Act 1995 (TSC Act), the ACT Nature Conservation Act 1980 (NC Act), or GEOGRAPHIC AREA AND AMPHIBIAN the Tasmanian Threatened Species Protection Act 1995 DIVERSITY (TSP Act) (Table 6.1). Ten of these species also are listed The geographic area covered by this chapter includes tem- as either Vulnerable, Endangered, or Critically Endan- perate south-eastern mainland Australia and all of Tas- gered on the International Union for the Conservation of mania (Plate 6.1). South-eastern Australia has a diverse Nature Red List (IUCN Red List). Four of the species are range of habitats and vegetation communities, from open listed only in Victoria on the Threatened Species Advi- grasslands to cool temperate rainforests. This broad varia- sory Lists (TSAL) (Table 6.1), which is a non-statutory list tion in habitats is related to variation in topography, rain- of species that may or may not also be listed under the fall, and fire regimes over this region, which includes the EPBC Act or the FFG Act. Although not currently listed southern portion of the Great Dividing Range, and moun- at either a state or national level, the Tasmanian treefrog tainous regions of Tasmania. Annual average rainfall Litoria burrowsae may be at risk of further substantial throughout this region varies from 500 to 2400 mm, with declines in the near future (Cashins et al. 2015). higher elevations on both the mainland and Tasmania Despite the possible extinction of six species further having a consistent cover of snow throughout winter north in eastern Australia (Skerratt et al. 2016), no spe- (Bureau of Meteorology 2017). Rainfall in this region gen- cies in south-eastern Australia are known to have erally follows a Mediterranean style pattern of wet winters become extinct. One species, the southern barred frog and drier summers; however, this contrast diminishes up Mixophyes balbus, has not been observed in this region the eastern coast of the mainland. since 2001, despite being found in reasonably high abun- Associated with this environmental heterogeneity is a dance further north (Hunter and Gillespie 2011). Five of broad range of freshwater aquatic habitats that support a 171106 Status of Conservation and Decline of Amphibians 2pp.indd 39 19/12/2017 09:33:19.15 40 Status of Conservation and Decline of Amphibians Table 6.1. Threatened frogs occurring in the part of south-eastern Australia covered in this chapter, and their current status at state level (New South Wales: Threatened Species Conservation Act 1995 [TSC Act]; Victoria: Flora and Fauna Guarantee Act 1988 [FFG Act], [TSAL]; Tasmania: Threatened Species Protection Act 1995 [TC Act]), Commonwealth level (Environment Protection and Biodiversity Conservation Act 1999 [EPBC]), and global level (International Union for the Conservation of Nature [IUCN] Red List of Threatened Species). CR = Critically Endangered, EN = Endangered, VU = Vulnerable, LC = Least Concern, DD = Data Deficient. National IUCN Species EPBC Act State Red List Green and golden bell frog VU NSW – EN (TSC Act) VU Litoria aurea Vic – Not listed (FFG Act) Vic – VU (TSAL) Booroolong frog EN NSW – EN (TSC Act) CR Litoria booroolongensis Vic – Threatened (FFG Act) Vic – CR (TSAL) Yellow-spotted bell frog EN NSW – CR (TSC Act) CR Litoria castanea Bleating treefrog Not listed NSW – Not listed (TSC Act) LC Litoria dentata Vic – Not listed (FFG Act) Vic – VU (TSAL) Littlejohn’s treefrog VU NSW – VU (TSC Act) LC Litoria littlejohni Vic – Threatened (FFG Act) Vic – EN (TSAL) Growling grass frog VU NSW – EN (TSC Act) EN Litoria raniformis Vic – Threatened (FFG Act) Vic – EN (TSAL) Tas – VU (TSP Act) Spotted treefrog EN NSW – CR (TSC Act) CR Litoria spenceri Vic – Threatened (FFG Act) Vic – CR (TSAL) Alpine treefrog VU NSW – EN (TSC Act) LC Litoria verreauxii alpina Vic – Threatened (FFG Act) VIC – CR (TSAL) Sloane’s froglet Not listed NSW – VU (TSC Act) DD Crinia sloanei Vic – Not listed (FFG Act) Vic – Not listed (TSAL) Giant burrowing frog VU NSW – VU (TSC Act) VU Helioporus australiacus Vic – Threatened (FFG Act) Vic – CR (TSAL only) Southern barred frog VU NSW – EN (TSC Act) VU Mixophyes balbus Vic – (FFG Act) Vic – CR (TSAL) Baw Baw frog EN Vic – (FFG Act) CR Philoria frosti Vic – CR (TSAL) Bibron’s toadlet Not listed NSW – Not listed (TSC Act) LC Pseudophryne bibronii Vic – Threatened (FFG Act) Vic – EN (TSAL) Southern corroboree frog CR NSW – CR (TSC Act) CR Pseudophryne corroboree Northern corroboree frog CR NSW – CR (TSC Act) EN Pseudophryne pengilleyi ACT – EN (NC Act) 171106 Status of Conservation and Decline of Amphibians 2pp.indd 40 19/12/2017 09:33:19.26 6 – Frog declines and associated management response in south-eastern mainland Australia and Tasmania 41 National IUCN Species EPBC Act State Red List Southern toadlet Not listed Vic – Not listed (FFG Act) LC Pseudophryne semimarmorata Vic – VU (TSAL) Martin’s Toadlet Not listed NSW – Not listed (TSC Act) DD Uperoleia martini Vic – Threatened (FFG Act) Vic – CR (TSAL) Striped mash frog Not listed NSW – Not listed (TSC Act) LC Limnodynastes peronii Vic - Not listed (FFG Act) Vic – Not listed (TSAL) Tas – EN (TSP Act) Giant banjo frog Not listed NSW – Not listed (TSC Act) LC Limnodynastes interioris Vic – Threatened (FFG Act) Vic – CR (TSAL) diverse range of frog species. At least 46 species occur in geographically isolated populations of P. corroboree, spot- the area covered by this chapter (Atlas of Living Australia ted treefrog (Litoria spenceri), and alpine treefrog (Litoria 2017). The distributions of these species range from high verreauxii alpina) (Hunter et al. 2009b, Clemann et al. elevations where only one or two species occur, to coastal 2009; Gillespie et al. 2015). Emergence of B. dendrobatidis areas where more than 15 species may occur in a relatively in these naïve populations was associated with rapid small area. There are 10 species found only in the region declines and extirpation, thereby providing direct and covered by this chapter, with a number of these having unequivocal evidence that B. dendrobatidis – in the very restricted distributions, such as the southern cor- absence of other threats – is capable of causing the loss of roboree frog (Pseudophryne corroboree), which was only populations. Despite the capacity for B. dendrobatidis to known from an area of 500 km2 (OEH NSW 2012a), and cause rapid demise, some remnant populations of all the Baw Baw frog (Philoria frosti) which was found only focal species have persisted. However, in remnant popula- in an area of 135 km2 (Hollis 2011). tions, B. dendrobatidis is an ongoing threat and the path- ogen’s presence is maintained by reservoir hosts (West 2016; Scheele et al. 2017b). A key reservoir species in the KEY THREATS AND CAUSES OF THE high country is the common eastern froglet (Crinia signif- DECLINES OF FROGS era), a widespread, highly abundant, non-declining spe- The primary cause of recent declines for many of the cies that often carries severe B. dendrobatidis infections threatened frogs covered in this chapter is the disease (Hunter et al. 2009b). Reservoir hosts can amplify the chytridiomycosis, which is caused by infection with the impact of disease in co-occurring species, and some amphibian chytrid fungus Batrachochytrium dendroba- threatened species are clearly persisting at greater abun- tidis (Berger et al. 1998, 2009). Precipitous declines asso- dance only in habitats where reservoir hosts are absent, or ciated with the emergence of B. dendrobatidis occurred in at low abundance (Scheele et al. 2017b). the 1980s and 1990s, consistent with major declines Although B. dendrobatidis has been the primary cause reported in other regions of Australia and globally of rapid and noticeable declines of frogs since the late (Hunter et al. 2010a; Gillespie et al. 2015; Scheele et al. 1970s, the pathogen’s impact on many species has been 2016, 2017a,b). Sampling museum specimens from the exacerbated by other threats that have reduced the frogs’ Australian Alps, Hunter et al. (2010a) found that chytrid geographic range and the resilience of their populations. fungus was absent in individuals collected before 1980, An alternative and practical way of viewing this is that B. but was common in specimens collected from declining dendrobatidis has increased their susceptibility to other populations during the 1990s, consistent with the hypoth- threats. Because we are currently limited in our ability to esis that B. dendrobatidis is an introduced pathogen in directly mitigate the impacts of B. dendrobatidis (Wood- the region. Mass declines associated with the initial hams et al. 2011), it is important to target other threats that emergence of B. dendrobatidis were unobserved; however, are more manageable. This is particularly the case when emergence has been directly observed in several loss and degradation of habitat is contributing to ongoing 171106 Status of Conservation and Decline of Amphibians 2pp.indd 41 19/12/2017 09:33:19.42 42 Status of Conservation and Decline of Amphibians declines. Widespread loss and degradation of habitats is populations remain large and robust in East Gippsland common in the tablelands, slopes, and lowland regions and (Gillespie 1996; Howard et al.