The Giant Barred Frog is the largest of the barred frogs and Australia’s second largest frog. Females are larger than males, having a snout-to-vent length (SVL) to 120 mm and weighing around 190 g. Males reach 88 mm (SVL) and weigh up to 80 g. The skin is finely granular above and smooth below. The dorsal surface is beige to dark brown with darker blotches. Typical of barred frogs, an irregular, dark, vertebral stripe is present. The stripe commences between the eyes and extends to the vent, sometimes breaking up into a series of blotches along the midline. The flanks are pale yellow with irregular dark spots or mottling. The ventral surface is yellow to white. The head is large and broad with a prominent projecting snout, giving the species a more triangular shape than other Mixophyes species. A black stripe commences at the snout and continues through the nostril and eye, extending over a distinct tympanum, before terminating at a point above the shoulder. The ventral surface of the chin is typically yellow with fine brown mottling. The upper lip has irregular darker markings. The eyes are prominent with a vertical Mixophyes iteratus (Giant Barred Frog) Conservation Advice Page 2 of 22 black pupil. The iris is pale silvery-white to pale gold and often brighter in the top half. The limbs are long and muscular and have a series of dark and pale crossbars of similar width along their length. The hind limbs are proportionately larger than in other Mixophyes species, with the back of the thigh ranging from black, with a few large yellow spots, to being marbled black and yellow. There is often a rust colouration along the outer toes and fingers. The fingers lack webbing, while the toes are fully webbed, with only the last two joints of the fourth toe free (as opposed to three joints of the toe being free of webbing in the other Mixophyes species). The outer metacarpal is poorly developed. The inner metatarsal tubercle is well developed but only half as long as the first toe (versus being nearly of equal length in the other Mixophyes species). Discs are absent on the toes and fingers.
Giant Barred Frog |
Mixophyes iteratus
Status: Vulnerable on the EPBC Act list
Government evidence of impact of climate change:
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Australian Government, Conservation Advice, Mixophyes iteratus
Climate Change Increased temperature Known Climate change is expected to cause a pronounced intensity frequency and current increase in extinction risk for frog species over the change to precipitation coming century (Hagger et al. 2013 Pearson et al. patterns 2014).
Climate projections for eastern Australia include reduced rainfall; increased average temperatures; and more frequent droughts.
Climate change impacts are compounded by the Giant Barred Frog s restricted area of occupancy; low population density at sites (particularly within the south of the species range); short generation length (4 5 years); and large body size.
These variables are identified as increasing the risk of local extinction (Oza et al. 2012 Hagger et al. 2013 Pearson et al. 2014) and are amongst the strongest predictors of species vulnerability to climate change (Pearson et al. 2014).
Tanner McAllister et al. (2018) developed conceptual models for four World Heritage National Parks to predict the likely impact to stream dwelling frogs from climate change.
This sort of event is increasingly likely to reoccur as a result of climate change.
However; the absence of the species from some historic locations; very low abundance at others (particularly in the southern limit of the range); and isolation of remaining subpopulations (DPIE 1999 Hines the South east Queensland Threatened Frogs Recovery Team 2002); together with the low dispersal ability (and associated poor recolonisation potential) of the species (Lemckert Brassil 2000); has reduced the likelihood of recovery from future extreme events associated with land clearing; climate change; or disease (Hagger et al. 2013).
The Giant Barred Frog is highly vulnerable to climate change; having physiological and ecological traits that confer both low resistance and low resilience to climate change.
Disease and climate change have already greatly impacted the population; with a decline in the 1970s to 1990s likely the result of Bd infection (Ingram McDonald 1993 Laurance et al. 1996 DPIE 1999 Goldingay et al. 1999 Lemckert Brassil 2000 Hero Morrison 2004 Lemckert Shoulder 2007 Hines 2012 Berger et al. 2016); and the impact of the 2019 20 bushfires suspected to be significant (see Criterion 1).
Further; the Giant Barred Frog is highly vulnerable to climate change; having the physiological and ecological traits that confer both low resistance and low resilience to climate change (Hagger et al. 2013 Tanner McAllister 2018).
Understand the potential influence of climate change on the long term survival prospects of the species; due to altered temperatures; rainfall patterns; bushfires; environmental stressors and diseases.
Increased Known Localised extinction of frogs has been observed intensity frequency of current through wildfire events.
An analysis by a team from the National Environmental Science Program (NESP) Threatened Species Recovery (TSR) Hub showed that 37 of the distribution of the Giant Barred Frog was affected by these fires (with 13 burnt in high to very high severity fire); and the estimated proportional population change for this species from pre fire levels to 1 year after the fire was an overall decline of 10 from pre fire levels; but that the decline could be as large as 37 (bound of 80 confidence limits) (Legge et al. 2021).
The fires may have accelerated any population decline; through direct mortality; and the unfavourable post fire conditions (loss of shelter; increased susceptibility to predators; and loss of prey); as well as a reduction in future recruitment (egg and tadpole death and breeding site degradation).
A structured expert elicitation process was used to estimate the proportional population change for this species from pre fire levels to immediately after the fire and then out to three generations after the fire; when exposed to fires of varying severity.
For comparison; experts also estimated the population change over time in the absence of fire by three generations; the overall population of the Giant Barred Frog after the fire was estimated to be four percent lower than it would have been had the 2019 fire not occurred (Legge et al. 2021).
Early observations in Queensland are that the 2019 20 bushfires affected some habitat of the low density subpopulation at Nixon Creek in Lamington NP; while more widespread and ecologically severe fire is likely to have had a significant impact on subpopulations at Canungra Creek and Coomera River in Lamington NP.
Given the extent of the 2019 20 bushfires; which are believed to have impacted 37 percent of the distribution range of the Giant Barred Frog (with 13 percent burnt in high to very high severity fire); these broad zones can be identified as three separate locations; each of which could be rapidly affected in a single bushfire season (which can involve multiple fire events).
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